S1049: Integrated Management of Pecan Arthropod Pests in the Southern U.S.

(Multistate Research Project)

Status: Inactive/Terminating

S1049: Integrated Management of Pecan Arthropod Pests in the Southern U.S.

Duration: 10/01/2010 to 09/30/2015

Administrative Advisor(s):


NIFA Reps:


Non-Technical Summary

Statement of Issues and Justification

The pecan industry now has a highly effective and sophisticated insect and mite pest management system in place that conserves the foliage and nut crop. This was achieved through research by the USDA/CSREES regional research projects in collaboration with extension specialists, private industry and cooperating pecan growers. Pecan foliage can be protected from aphid and mite feeding injury with bottom-up control methods where fertilizers, pesticides and ground cover plants are applied to the soil or with top-down control methods where the foliage is treated directly (usually with an airblast sprayer) with: insecticides; miticides; repellents; biological control agents, such as, insectary-reared insects and mites or cultured-microbes or their byproducts; natural products, primarily plant extracts; or soaps and surfactants that modify the leaf surface. Pecan nuts are currently protected by top-down controls with insecticide sprays timed to be applied when the pest populations occur in the orchard in sufficient abundance to cause economic injury to the crop. The key to effective nut pest control is to have an effective insect monitoring program ongoing in the orchard from budbreak to harvest. Pecan growers, throughout the U.S., have many control options including both federally registered insecticides and miticides and proven biological controls. Scouting techniques are also effective, well-known and used by a significant portion of growers. The system is not static and changes from season to season because of four main factors. First, INNOVATION leads to the development of new and more effective control methods each year. Second, REGULATION of insecticides and miticides can result in the gain/loss of their registration for use on pecan. Third, SELECTION within pest populations can develop a tolerance or resistance to certain chemical controls. Fourth, STATUS of the orchard changes with each season with respect to: climate; types and abundances of pests; value and size of the nut crop locally and across the region; and costs of production. The regional research approach has been an effective forum for finding alternative insect and mite controls and monitoring methods for pecan growers in the southern region of the U.S. since 1976. The current project S-1017, terminates on September 30, 2010 and the following narrative outlines our research plans for 2010 to 2015 seasons. Cooperating States Agricultural Experiment Stations and Agencies are: (Alabama, Florida, Georgia, Louisiana, Texas, USDA).

The need for research as indicated by stakeholders - Pecan growers universally demand improvements in insect and mite pest management. No pecan growing region is without some type of arthropod pest problem and multiple problems are the norm. Differences occur between the pecan growing regions in the portion of the insect or mite pest complex that is abundant at a sufficient level to cause economically significant injury to the trees, foliage or the nut crop. California, Arizona, New Mexico and West Texas pecans typically have aphid and mites on the foliage and pecan nut casebearer and hickory shuckworm as nut pests. In East Texas and north to Oklahoma to southeastern Kansas then east through to the east Atlantic Coast of Georgia the major pecan insect and mite pests are: aphids, pecan weevil, pecan nut casebearer, and hickory shuckworm. Pecan leaf scorch mite and Prionus root borers are key pests east of the Mississippi River in the southeastern U.S. Recent crop profiles for pecan production in Georgia (Guillebeau 2001) and Texas (Smith et al 2002), Kansas (Kadir et al 2001), North Carolina (Parker et al 1999), and Arkansas (Johnson et al 2003) indicate that the pecan weevil and kernel feeding hemipterans are the major late season kernel pests facing the U.S. pecan industry.
Insecticides are the main controls used for reducing damage by these two pest problems. The research committee of the Georgia Agricultural Commodity Commission for Pecan ranks black pecan aphid as the most serious foliage feeding insect pest. Stakeholders also want better resources placed on the internet to aid their in-season decision making on key pests.

The importance of the research work, and consequences if it is not done - Since 1976, regional research in the southern states on pecan entomology has produced effective methods for detecting, predicting and managing insect and mite outbreaks in pecan orchards. Pecan orchards that are not managed for insect and mite control each season will typically stop producing a significant nut crop within two seasons. The damage potential of the nut feeding insects is sufficient to injure or destroy the entire nut crop each year and foliage insects can defoliate the trees early in the season throwing the trees in to a non-productive period that can last for several seasons (Dutcher et al 1984).

The technical feasibility of the research  The primary problem in accomplishing pecan research goals is the establishment of a research site for field experiments to test new control methods. Prior to 1976, most of the field experiments were run on the farms of cooperating growers often without nontreated controls and only limited (or no) local controls, randomization and replication of treatments. Since 1976, several experimental sites have been planted and are available for controlled field experiments under more uniform conditions at state agricultural experimental stations (SAES) and the USDA field stations. The work at these locations has produced control methods that are thoroughly tested, interpreted, analyzed, refined and retested in statistically valid experiments. The trials determine the efficacy as well as the probability of achieving the efficacy. Methods developed at these sites are readily transferred to commercial orchards. Also, efficacy trials at the SAES sites have found methods that are ineffective or cause ancillary problems, such as, resurgence of secondary pests, or insecticide resistance and pest replacement problems. Biological control methods are new to pecan growers. Advantageous interactions between cultural methods and pest populations are recently measured and just now being understood and manipulated by growers. Considerable extension and educational efforts will have to be initiated to ensure that growers understand how to use these new ideas in the field. As examples: identification of beneficial insects and mites will become important and is not a skill that most growers have at this time; more frequent application of reduced rates of fertilizer coupled with aphid and mite scouting information is not currently practiced by growers; the use of clover as an intercrop is widespread but the movement of predators from the cover crop to the tree with food sprays and sicklebar mowing is not a common practice; identification of the fungi that attack aphids and coupling reduced frequency of fungicide sprays to encourage these fungi is not commonly used by growers. The implementation of these known positive interactions is typically not associated with increased input costs and has been shown to be effective in research trials and limited grower demonstrations. Additionally, new developments in Information Technology provide a novel opportunity to develop deliverables with complex underpinnings using the computer and posting results on the internet. The initial phase for this has been established at http://pecan.ipmpipe.org/

The advantages for doing the research work as a multistate effort  The advantages of working as a team of entomologists across the pecan growing regions are: 1. Methods can be innovated at one location and then tested under a broad range of conditions and then altered to fit the conditions at each region; 2. Information of recent work can be presented and discussed each year by all participants so that scientists can access the results before the material is published since the publication process can take a year or more; 3. Regional experiments can be conducted during the same season to measure the influence of environmental factors on the efficacy of the control methods and seasonal occurrence of the pests; 4. Extension specialists and growers and publicists can be invited to the annual meetings to make presentations on important issues giving the technical committee members a better perspective on conditions in the pecan industry.

What the likely impacts will be from successfully completing the research work -Compare the % mortality required to prevent annual increases in the insect and mite populations (Table 1) with the relative efficacies of the current control methods (Table 2) and it is obvious that improved control methods are needed against all the key insect and mite pests listed.
Table 1. The mortality that is needed each season to cause a reduction in the season to season abundance are estimated from literature values for the reproductive capacity (RC) and generation time (GT) for certain pecan insect and mite pests with the formula:


% Mortality = 100´ (1  (1 ¸ (SR ´ RC)GT)).

Pest* Reproductive Capacity Generation Time % Mortality

Pecan weevil 75 eggs/female .33 or .50 gen/yr 3053/season**
Pecan nut casebearer 50-150 eggs/female 2 gen/yr 99-99.9/season
Hickory shuckworm unknown 2-5 gen/yr unknown
Black pecan aphid 35 nymphs/female 26 gen/yr 99.9/season
Yellow pecan aphid 38 nymphs/female 32 gen/yr 99.9/season
Black margined aphid 125 nymphs/female 16 gen/yr 99.9/season
Pecan leaf scorch 9-36 eggs/female 7-8 gen/yr 99.9/season
Mite
Fall webworm 300-1000 eggs/female 4 gen/yr*** 98-99.9/season
Walnut caterpillar 120-880 eggs/female 2 gen/yr 99-99.9/season

* Kernel feeding hemipterans are not listed since they invade the orchard and do not breed in the orchard.
** 97.3 % mortality per generation is required to prevent pecan weevils from increasing in the orchard. 30 % (53%)mortality per year will control weevils with a 3 (2)year life cycle.
*** 2 overlapping broods occur each season

Table 2. Control methods for the eight major pecan arthropod pests in North America.

Pest Control method for pest Relative efficacy

Pecan weevil Broad spectrum insecticides High
Curculio caryae (Horn) Quarantine High
Risk rating and spot treatment Moderate
Trunk treatment Moderate
Entomopathogens, nematodes Low
Red imported fire ant as predator Low

Pecan nut casebearer Broad spectrum insecticides High
Acrobasis nuxvorella Biorational insecticides High
(Neunzig) Mating disruption Low

Hickory shuckworm Broad spectrum insecticides High
Cydia caryana Fitch Biorational insecticides High
Sanitation Moderate

Black pecan aphid Organophosphate insecticides High
Melanocallis caryaefoliella Neonicitinoid insecticides Moderate
Davis Insecticidal soap High
Harmonia axyridis (Pallas) Moderate
Interplanting crape myrtles Low

Yellow pecan aphid Soil applied systemic insecticides High
Monelliopsis pecanis Bissell Neonicitinoid insecticides High
Insecticidal soap High
Harmonia axyridis (Pallas) Low
Introduced parasites Low

Blackmargined aphid Soil applied systemic insecticides High
Monellia caryella Fitch Neonicitinoid insecticides High
Insecticidal soap High
Harmonia axyridis (Pallas) Low
Introduced parasites Low

Pecan leaf scorch mite Miticides High
Eotetranychus hicoriae Sulphur High
(McGregor) Predatory mite release Moderate
Dormant oil sprays Low

Kernel-feeding Hemipterans Broad spectrum insecticides Moderate
Pentatomidae and Coriedae Trap crops Low
Removing alternate host plants Low

* Control methods listed in the table have shown benefits greater than the costs.

** Efficacy ratings: Total = 100%; High - 96% to 99%; Moderate  80 to 95%; and, Low < 80%.

The impact of the research is nothing short of saving the U.S. pecan crop each season from devastating insect and mite injury. The reproductive potentials of the insect pests translate into significant damage potentials when the insects and/or mites occur at levels of abundance that cause economic injury to the tree, foliage and nuts. The new control and delivery methods will however require more extension and educational efforts to be effectively applied by pecan growers. Training is needed in the identification of beneficial organisms and interactions between methods.

Related, Current and Previous Work

The insect complex associated with pecan in native and improved systems includes 180+ species of phytophagous insects (Payne and Johnson 1979, Harris 1983) and each is associated with a diverse array of natural enemies (Tedders 1985). Insect management strategies range from total reliance on natural enemies to intensive integration of chemical and biological controls (Dutcher et al. 2003b). The fruit and foliage in pecan orchards are susceptible to insect injury that can result in economic losses continuously for seven months each season. Preventive insecticide applications are not practical over this long period of time. For example, the first defense against aphid injury is the enhancement of insects that prey on aphids, so-called aphidophaga. The second defensive method is to adjust the fertilizer application rates and times to prevent a flush of nitrogen in the leaf that causes an increase in the reproductive rate and survival of the pecan aphids. The third defense is the find pesticides for control of nut feeding pests that do not disrupt natural control of the pecan aphids by aphidophagous insects and entomophagous fungi. The final defense is to apply an aphidicide.

Safer Insecticides. - Chemical control strategies for pest outbreaks in pecan orchards have shifted in recent years from a reliance on broad-spectrum insecticides to the use of biorational insecticides that are safer for the applicators and the environment as well as beneficial insects and mites. Initially, insect growth regulators were evaluated for insect control against pecan weevil and lepidopterans (Payne and Dutcher 1985, Tedders 1977). Efficacy was much lower than the broad-spectrum insecticides and registration was not pursued. Broad-spectrum insecticides became the main control measures for preventing pest damage and are currently the only effective controls for pecan weevil, hickory shuckworm, kernel-feeding hemipterans and black pecan aphid. Recently, newer insect growth regulator insecticides have gained acceptance among growers for control of lepidopteran pests (Dutcher et al 2003a). However, the effective use of insect growth regulators in pecan orchards relies on an effective monitoring and prediction of oviposition and date of first significant injury for pecan nut casebearer and long residual activity for effective control of hickory shuckworm. Growers in Georgia, however, have found that pheromone trap catch is not related to the amount of damage by pecan nut casebearer. For these growers, a spray of chlorpyrifos at the time when the first nut injury is found in the orchard has better efficacy than the insect growth regulator sprays at the time of nut injury predicted from scouting (R. Grebel, personal communication).

Insect-Orchard Interactions. - Scientific literature on pecan IPM has many records of relations between insect outbreaks and orchard conditions. Various management techniques, tree phenology, cultivars, and weather events and conditions all affect insect and mite populations. As examples, pecan cultivars and trees of different ages (sizes) differ considerably in susceptibility to injury by pecan weevil, kernel-feeding hemipterans and black pecan aphids (Dutcher et al. 2001, Kaakeh and Dutcher 1994, Worley and Mullinix 1997) and most growers have detailed maps of the orchard that had cultivars and tree age. Yet entire orchards are sprayed at the same time with the same chemical control when considerable savings could be accrued if the only more susceptible trees were treated. Certain pecan cultivars have a narrow window of susceptibility to pecan weevil oviposition with either a short kernel development time, or an early or late onset of kernel development (Harris 1985). Weevil can be controlled in these cultivars with 2-3 applications of carbaryl compared to 4-5 applications for standard cultivars. Significant risk of hemipteran kernel damage is associated with pecan cultivar and with legume plantings (and other alternate host plants) adjacent to the pecan orchard. Spot treatments of insecticide sprays to the trees in the first two border rows adjacent to the alternate host plants are effective in reducing stink bug damage (kernel spot) throughout the orchard. Legume trap crops between the trees and the alternate host plants are effective and have been used by pecan growers for reducing kernel spot. Black aphid populations on susceptible cultivars cause significant leaf damage and defoliation at population levels of a few aphids per leaf (Wood and Reilly 1998). However, on less susceptible cultivars the onset of the outbreak is often several weeks later than on susceptible cultivars.

Optimism for the effectiveness of precision applications of carbaryl to tree trunks and spot treatments in highly infested portions of the orchard stems from recent reported research results that indicate that nut damage in a pecan tree is significantly correlated to the density of pecan weevils emerging from the soil directly beneath the tree (Dutcher et al 2003a). In early replicated field trials, trunk sprays effectively killed adult weevils on the trunk for up 13 days after application of carbaryl (Cottrell and Wood 2003). It has been estimated that 70  80 % of the adult weevils, fly to the trunk first (Raney and Eikenbary 1968) and could thus be targeted for insecticide application to manage pecan weevils. This could reduce entire canopy sprays, which are known to be detrimental to natural enemies and flare aphid and mite populations (Dutcher and Payne 1983). The trees in native groves have a unique nut phenology in each tree adding to the variability in pecan weevil distribution (Reid and Mulder 2003). Spot treatments of only the weevil infested portions of the pecan orchard has not been tested as a pecan weevil control method. Pecan weevil distribution in the orchard can be estimated from tree-to-tree measurements of % nut damage, crop load, and known population parameters of the weevil (Harris 1985) and then validated by extensive trapping of emerging adults with cone emergence traps from a known area of the soil surface (Raney et al.1970). Accurate weevil distribution maps would allow the precision application of soil applied biocontrol agents and foliage and trunk sprays of carbaryl, thus reducing costs. Research is needed to determine if spot spraying infested areas in orchards with localized infestations of weevils will effectively prevent nut damage in the entire orchard.

Intercrops. - Previous studies have shown increased diversity and abundance of native aphid-feeding insects (aphidophaga) by planting intercrops in pecan orchards. Crapemyrtle aphid, commonly infests crape myrtle in the southeastern US and is a natural prey of multicolored Asian lady beetle in Southeast Asia. Crape myrtle interplanted in pecan orchards may be important in increasing multicolored Asian lady beetle populations (Mizell and Schiffhauer 1987). Significantly higher populations of lady beetles were found in various cool (Bugg et al 1990) and warm-season (Bugg and Dutcher 1989) covers. Rice et al. (1998) found clover plus vetch to harbor significantly larger populations of lady beetles than mowed grass cover. Unfortunately in both cases biological control of pecan aphids did not increase significantly. Even though Rice et al. (1998) did not find a significant increase in biological control overall in groundcover-enhanced orchards, they did observe an increase in one isolated orchard where multicolored Asian lady beetle had recently become established. Red imported fire ants can impede biological control by attacking other natural enemies of pecan aphids. Dutcher (2004) observed greater biological control of pecan aphids when red imported fire ants were kept out of trees with an insecticide applied to tree trunks. Combinations of red and white clovers or clover plus vetch also provide adequate nitrogen for pecan tree nutrition (Diver and Ames, 2000).

Ant Control - Insects are a major source of nutrition for red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae). These ants are important predators of pests including southern green stink bug (Krispyn and Todd 1982), cowpea curculio (Russell 1981) and pecan weevil (Dutcher and Sheppard 1983). Pecan weevil larval populations are consistently reduced by 33% after the larvae drop to the soil surface from the pecans and before they burrow into the ground (Dutcher and Sheppard 1981). Red imported fire ants also interact with aphids and aphidophaga in the pecan trees (Tedders et al 1990). Ant foraging can be partitioned with insecticide barriers sprayed on the tree trunks so that red imported fire ants will remain on the soil surface to prey on weevils and not interfere with aphidophagous insects in the trees. The effect of these trunk sprays has been effective in reducing aphid populations in the Desirable trees in Georgia (Dutcher et al 1999) and ineffective in reducing aphid populations in Cheyenne trees in Texas (Harris et al 2003). Red imported fire ants can tunnel under the insecticide barrier without becoming intoxicated and produce a trail to the tree crown, esp. on older trees with heavy bark. Farnesol, an ant repellent that forms an impassable odor plume around the trunk successfully prevents Argentine ants from foraging in citrus trees (Shorey et al 1996). Current research has found that farnesol was not an effective repellent of ants on pecan trees but certain plant extracts (neem extract, sesbania extract), natural compounds (methyl anthranilate, methyl myristate) and an industrial repellent (methyl carbitol) are effective ant repellents that prevent foraging in pecan trees (Dutcher, manuscript in press).

Trap Crops. - Two conditions of pecan known as black pit and kernel spot are caused by several species of true bugs belonging to the families, Pentatomidae and Coreidae. Initially, black pit and kernel spot were thought to be caused by diseases and treated as such until it was proven (Adair 1927) that these conditions were caused by several species of kernel feeding hemipterans. The primary kernel feeding hemipteran pests of pecan include the southern green stink bug, Nezara viridula; green stink bug, Acrosternum hilare; brown stink bug, Euschistus servus ; Dusky stink bug, Euschistus tristigmus and the leaffooted bugs Leptoglossus phyllopus and L. oppositus. All of these insects are phytophagus and feed on a wide range of plants (McPherson and McPherson 2002). Stinkbugs find crops such as cowpeas and soybeans more appealing than pecan trees when plots of these crops are planted near pecan orchards, gravitating toward the trap crop and away from the trees. The primary challenges pecan producers face in managing these pest include the lack of economic thresholds to make management decisions, the long period of susceptibility to damage (nut set to harvest), the difficulty in scouting for damaging populations and the limitations on insecticide use near harvest. Leguminous trap crops, sown adjacent to seedling and improved pecan orchards, effectively and consistently reduce the incidence of kernel spot by 50% in improved pecan orchards (Smith 1996, 1999). The trap crops are sprayed as the pods mature with an insecticide to kill the hemipterans before they enter the orchard (Coolman 2003). Growing trap crops is beneficial for owners of small pecan orchards, as well as people who want to grow their pecan crops organically. Growing a trap crop around the orchard will control stink bugs without spraying the trees (Smith 1999). Sunflower, sorghum and millet are also attractive to kernel-feeding hemipterans and produce seed that is attractive to hemipterans in the early fall at the same time as the pecans are susceptible to kernel spot. Mizell et al. (2008) have recently developed a generic trap cropping system that attracts the primary stink bug pests- the brown, dusky, green, southern green and leaffooted bugs as well as many of the minor stink bug species. This scheme is neutral relative to farm scale and farmer philosophy and can be used in large containers for small acreage, organic or homeowners. Stink bug damage phenology varies across the pecan belt often occurring throughout most of the growing season in the central states (Smith 1996, 1999), but occurring mostly in fall in the eastern states (Dutcher and Todd 1983). The trap crop is customizable for the entire growing season and relies on fall plantings of hairy vetch, crimson clover and triticale for early spring, followed by buckwheat, sunflower, sorghum and millet for the rest of the season. Millet and sorghum can be ratooned to extend the life of plantings reducing establishment costs and buckwheat can be used as relay crop for quick maturity because it matures attractive seed within 5 weeks of planting. All of these trap crop species provide the additional ecological service of enhancing biological control agents and pollinating species as well as providing food for wildlife (Mizell et al. 2008). In addition, yellow traps and stink bug pheromones (Mizell and Tedders 1995, Mizell et al. 1996) are available to increase the efficacy of trap crops by increasing the attraction of stink bugs to the plots away from the orchard. Trap crops must be strategically placed to intercept stink bugs as they move into the orchard and more research is needed at the landscape level to determine and exploit these ecological relationships.

In native pecan groves, trap crops or broad scale application of pesticides to control stink bugs populations are not practical since livestock and poultry are part of the system. The mid-summer weeds in the groves are attractive to kernel-feeding hemipterans and the weeds provide a place for stink bug populations to develop within the grove itself and mowing of these weeds is an alternative control technique. Trap crops also provide excellent food for quail. Many pecan growers already plant small grains near the orchard border in the fall to feed wildlife and improve hunting, esp. for quail.

Vertebrate Predators. - Pecan growers have developed an interest in insectivorous birds and bats as vertebrate predators of pecan insect pests. Insects are a major source of nutrition for free-range poultry. Turkeys, chickens, Muscovy ducks and guineafowl are well adapted to free-range production in the southern U.S. Free-range poultry on the pecan orchard floor may be compatible with pecan production if the birds effectively control pecan weevil and kernel feeding hemipterans and eliminate the need for late season insecticide sprays. Turkeys are used for insect control in tobacco. In pecan orchards free-range turkeys eat insects but also will eat pecan nuts. Muscovy ducks are effectively used by pecan growers in New Mexico for insect control. Ducks have also been used for fly control on dairy farms and insect, snail, and slug control in gardens. Guineafowl have a diet that consists primarily of insects and small seeds. Guineafowl control insects in pastures and gardens (Fanatico 2002). Guineafowl also control the Lyme Disease-bearing deer tick (Duffy et al 1992). Growers indicate that guineafowl control June Bugs and Japanese Beetles and forage for soil insects in vineyards and one grower was able to control pecan weevil and kernel-feeding hemipterans in northern pecan trees by free-ranging 13 adult birds on a 13 acre orchard. These are only testimonials but many successful insect monitoring and control methods in fruit and nut crops began as early observations of growers or techniques devised by growers. Guineafowls natural diet is a high protein mix of small seeds (pecans are too large) and insects and the birds can be trained to stay in the orchard by supply supplemental feed at regular locations (Darre 2001). Guineafowl prey on insects during the day and roost in the trees away from predators at night. Insectivorous bats are voracious feeders and compliment the free-range poultry by preying on moths and other insects starting at dusk until dawn. Two species commonly cultured or enhanced in Georgia pecan orchards are Brazilian free-tailed bat, the evening bat and the southeastern myotis. Apparently pest populations declined soon after bats were enhanced by setting out bat houses near the orchards.

Predatory Mite Release.  Native phytoseiid mites (predators of pecan leaf scorch mite) in U.S. pecan orchards are a diverse group yet in improved orchards pecan leaf scorch mite outbreaks are very common. Introduction of western predatory mite, Galendromus occidentalis, has been successful in young trees (20 years) and early indications are that they can also become established in older pecan trees. The level of pecan leaf scorch mite control varies, however, from very good to none. Western predatory mite will feed on pecan leaf scorch mite and the predators will disperse from one tree to the next. Populations of the predators also increase by the end of the season and in young trees populations will carry over to the next season.

These new insect and mite control methods can be used by pecan growers to reduce insect pest populations to manageable levels. The overall goal of the regional research efforts is to maintain effective pest control for the pecan industry in the U.S. This will be accomplished by research in the development of: more effective monitoring and forecasting methods to measure and predict the activity of insects and mites in the orchards; improved control methods for key insect and mite pests that are effective and maintain or improve nut production; and, web-based integration techniques that enable pecan growers to access to pertinent information for making decision in pest management that will be compatible with their pecan production methods.

Objectives

  1. Improved Monitoring and Forecasting Methods for Field Populations of Pecan Arthropods
  2. Improved Control Systems for Pecan Arthropod Pests
  3. Integrate Pecan Arthropod Pest Control Methods with Pecan Production Methods
  4. Develop real-time Decision Aids for Delivery on the Internet

Methods

Research Sites. Over 300 acres of pecan orchards are available for the field trials Georgia, Louisiana, Arkansas, Texas, Florida and U.S.D.A. for research and demonstration plots. The high acreage is needed for the proposed research because trees are the sample units for many experiments and tree density ranges from 10-27 trees per acre. As examples, areas for research include: Cultivar evaluations can be conducted at University of Georgia at Tifton in a provenance collection where numerous bearing pecan trees of old and new cultivars are planted and cultured for research. The University of Georgias Coastal Plain Experiment Station in Tift Co., Ga. with 50A of 20 year-old pecan trees at Ponder Farm, 33A in at the Southeastern Branch Station near Midville and 35A of leased pecans near Plains. USDA-ARS Research Station, Byron, GA contains approximately 400 A of pecan for research purposes, the pecan blocks are interspersed with peach and forested land (the total area of the research farm is approximately 1200 A). Biological sources. Pecan insect and mites for various proposed bioassays will be produced naturally at highly infested and nontreated orchards. Pecan weevil adults will be collected by mass trapping with emergence traps; larvae will be collected as they emerge from early harvested, infested nuts at the Plains, Carter, Cook and Midville Farms. Kernel-feeding hemipterans will be collected from insecticide-free plots of legumes, sorghum and millet planted at the Coastal Plain Experiment Station. Blackmargined and black pecan aphids are ubiquitous and easily collected in large numbers from infested pecan trees. Microbial control agents will be produced on-site or purchased from commercial suppliers. Laboratory colonies of black pecan aphid, yellow pecan aphid and blackmargined aphid will be maintained on greenhouse-grown pecan seedlings. Brown stink bugs are polyphagous and easily collected in pheromone traps throughout the summer and early fall. Statistical Analysis of Data. Standard software used for analysis will be SAS v. 9.2 (SAS 2008) though alternatives such as Microsoft Excel (Microsoft 2007) enhanced with Poptools (Hood 2009) will also be used for data storage and analysis. Each variable measured in controlled replicated trials will be analyzed for distribution and normal variables or variables transformed to approximate the normal distribution will be analyzed by univariate analysis of variance. Significant differences (P< 0.05 level) between treatment means will be determined by the appropriate mean separation procedure, e.g. LSD-test for simple experiments with 2 or 3 treatments, Scheffe test for trials more than 3 treatments and with unbalance design, Tukeys test for large experiments with balanced design. Relative variance will be estimated by calculating the coefficient of variance for each random variable and those with CV > 50% will be interpreted with caution (Steel and Torrie 1980). Objective 1. Monitoring and Forecasting Methods 1.1 Georgia and Florida - Identify semiochemicals (host-plant volatiles and pheromones) for attracting weevils to traps, and repelling weevils from pecan nuts. Surface extracts of the pecan shuck have many volatile compounds that may attract pecan weevil adults. These compounds (91 compounds from hexane extraction and 214 compounds from solid phase microextraction) have been identified by GC-MS (Harrison and Mizell, unpublished work in progress). Compounds will be tested for attractiveness in the field each season. Baited traps will be compared to non-baited traps and compounds that attract more adult pecan weevils will be combined in mixtures and tested for attraction in the field. 1.2 Georgia - Pheromone baited aerial malaise and pitfall traps will be compared as monitoring and control methods for Prionus root borers. The protocol places the pheromone over the opening to a pail-shaped (~1 l cap.) pitfall trap with the sides sprayed with RainX to prevent the beetles from crawling out. In 2009, these traps successfully caught Prionus laticollis and P. umbricornus adult males. The pheromone is anticipated to be commercially available in 2010. During the course of the proposed research project, experiments will be conducted to compare trap catch in traps place along the border of the orchard to trap catch in traps placed in the center of the orchard. Traps for female Prionus spp. beetles will be developed as pitfall traps amended with vanes radiated over the ground out from the center of the trap so that beetles will follow the vanes into the trap once the encounter the distal end. The pheromone tested in 2009 was derived from P. californicus and were attractive to southeastern Prionus spp. (P. laticollis and P. imbricornis) 1.3 Georgia  A comparison of beneficial insects in the tree canopy and on the orchard floor will be assessed with sticky boards fastened to the tree limbs for ladybeetles and lacewings, and malaise traps for parasitic hymenopterans, and syrphid and dolichopodid flies. Experiments will compare the canopy vs. orchard floor insects in plots with different types of ground covers or intercropped plants that have shown promise as habitat for beneficial insects. These plants include red clover, buckwheat, sesbania and crape myrtle. We will also test attractants for beneficial insects for their ability to cause migration of beneficial insects from the orchard floor to the tree canopy. Pheromone traps have been developed for lacewing adults and we have show that the traps are more effective when the pheromone is combined with plant volatile compounds. These traps will be tested as monitoring tools and the pheromone + volatiles combination will be tested as an attractant to cause migration of the lacewings to the pecan tree canopy. 1.4 Louisiana - Pecan phylloxera emergence data will be collected from orchards known to have infestations of pecan phylloxera located throughout Louisiana and southern Arkansas. Orchards will be selected from north to south and east to west across the state. The method used for obtaining the emergence data will follow the procedure outlined in Hall et. al., 2006. Bud development will be documented and photographed on each sample date. Consultation with a statistician will determine the appropriate statistical procedure to use for analyzing the data. 1.5 USDA - Aphid distribution on leaf surfaces, resulting from different feeding requirements, will be determined followed by a determination of aphid predation rates by lady beetles and lace wings resulting from the differential distribution of aphid species on leaf surfaces. Distribution of pecan aphid spp. on leaf surfaces will be examined in the laboratory and in the field. Laboratory assays will consist of examining nymph occurrence on upper or lower leaf surfaces when a) adults of a single species are placed on one leaf surface or the other, b) adults of a single species are released and allowed settle on leaf surfaces of their choice, c) similar numbers of adults of all species are released and allowed to settle on leaf surfaces of their choice. Field data on aphid distribution will also be collected. Predation experiments will be done in the lab using larval lacewings and coccinellids. Larval search patterns on leaf surfaces will be documented along with aphid survival for the different leaf surfaces. 1.6 Regional Research (All states and U.S.D.A.) - Integration of weather and trapping information with biorational insecticides for control of pecan nut casebearer. Trapping of adult moths, egg laying and first nut damage will be measured in similar experiments across the pecan belt. The time of and duration of occurrence of these insect activities will be correlated with climatic variables at the trapping sites to further define existing degree-day driven models. The emergence of the adults is later in the north than in the south and apparently the differences can be described by the accumulation of degree-days at each location. The research basis for the degree-day model, however, lacks any direct measure of the effects of temperature on insect growth, development of metabolic rate. The current prediction model uses degree-days calculated from a base temperature interpolated from the correlation of field catch at different locations to the accumulated degree-days at each site. Objective 2. Control Methods 2.1 Georgia - Mite pest management will be developed by integrating biological and chemical control methods. Phytoseiulis persimilis and Galendromus occidentalis have been shown to be effective as biocontrols of pecan leaf scorch mite. The predatory mites will be purchased and released in six commercial pecan orchards in Georgia (three orchards will receive P. persimilis, three orchards will receive G. occidentalis) as an inoculative release (release mites in one tree per acre) during the Fall of the first season of the project. Each month from July to Oct the abundance of pecan leaf scorch mites and phytoseiid mites will be monitored in the release tree and trees adjacent to the release tree and trees two tree spaces from the release tree. These orchards will be managed without any changes from the growers standard methods. The demonstrations will continue for three seasons. Techniques for the transfer of predatory mites from donor orchards  orchards where predatory mites have been released in the previous season and have successfully overwintered and become established  to recipient orchards that lack predatory mites yet have pecan leaf scorch mite will be developed for pecan by testing methods that have been successful in fruit crops. Overwinter predatory mites will be collected by pruning limbs in the donor orchard and affixing them to limbs in the recipient orchard during the early spring before budbreak. Budbreak in pecan occurs later in the spring when ambient temperatures are already over the thermal threshold for mite activity. The transfer of overwintering mites will be tested at three dates in mid-January, mid-February and mid-March. The second technique is to transfer leaves with predatory mites from the donor site to the recipient site during the summer and fall. This technique will be tested on three dates. Successful transfer techniques will create a sustained system and eliminate the purchase insectaries after the initial purchase. 2.2 Georgia  Vertebrate predators will be investigated as possible biological controls. Mexican free-tail bats may be important predators of lepidopteran pecan pests. A grower cooperator has an organic pecan farm near Quitman, Georgia that has several bat houses standing within the orchard and these are seasonally occupied by thousands of Mexican free-tail bats year. One impact of the bat feeding on insects may be a reduction in pest damage by pecan nut casebearer and hickory shuckworm. Research is underway to detect DNA from these two pecan insect pests in the excrement of the bats that is collected beneath the bat houses. Insect pest injury, light trap catch and pheromone trap catch in the organic farm with bats will be compared to injury and trap catch in pecan trees near at one mile distances from the organic farm to determine if distance from the high concentration of bats has an effect on these parameters. 2.3 Louisiana - Trees of different ages and bark thickness will be used to evaluate the efficacy of trunk sprays for control of pecan phylloxera. Comparisons will be made between application dates and bark thickness to determine if the method is viable and, if it proves efficacious, the optimum time to apply the insecticide application, and the maximum bark thickness at which control is achieved. Trees with surface applied irrigation will be used for evaluating the efficacy of a fall applied systemic insecticide for control of pecan phylloxera emerging the following spring. Rates to be used, timing of application, and method of application of the insecticide will be determined upon consultation with the manufacturers product development representative. A single application of an insecticide will be applied at each of the seven stages of bud and leaf development. The experimental design used will be either a randomized or randomized complete block design with a minimum of four trees per treatment, with each treatment being a single insecticide application made at each of the seven stages of bud and leaf development. Insecticide trials will continue to be conducted at the Pecan Research-Extension Station and at commercial pecan orchards. The experimental design used for the trials will either be a randomized block or randomized complete block design with four trees per treatment. Sampling methodology used will depend upon the arthropods being targeted. The effects various insecticides have on non-target arthropods and resurgence of secondary pests will be evaluated as well. Various devices will be used to capture non-target arthropods following treatment applications, while counts of secondary pests (i.e. yellow aphids, mites) will be made at 3, 7, 14, and 21 days following treatment applications. Methodology is currently being discussed with potential collaborators to evaluate procedures to be used for determining the modes of resistance to the formation of galls by pecan phylloxera. Investigations into the modes of resistance will again look at phenological differences between cultivars, morphological differences in plant tissue, and at possible biochemical differences. 2.4 Regional Research (All states and U.S.D.A)  New chemical microbial controls for pecan insects and mites will be evaluated for efficacy in controlled field experiments with a nontreated control and standard pesticide treatment. Insects and mites will be monitored by standard methods in the plots and treatments will be applied when a pest population reaches a level of abundance greater than the prescribed action or economic threshold level. Plots will be monitored for the injury caused by the pests and for the abundance of secondary aphid, leafminer and mite pests to determine if the new treatments cause secondary pest resurgence. Baseline toxicological data will be collected by using laboratory bioassays of the mortality caused by a series of concentrations of the new insecticides or miticides to a sample of the pest population collected from the field. Typically, a slide dip bioassay is effective for aphids, bollweevil test is effective for pecan weevil and treated leaf disc bioassay is effective for pecan leaf scorch mite. Bioassays for pecan nut casebearer and hickory shuckworm have not been developed due to the lack of an effective rearing method. Gregarious caterpillars  fall webworm and walnut caterpillar  can be tested by treating whole leaves and excising the leaflets and feeding them directly to the caterpillars. Novel microbial controls and entomopathogens such as previously untested nematode or fungal strains or species will be tested under laboratory conditions for virulence to pecan weevil or other major pecan pests based on Shapiro-Ilan et al. (2003). If laboratory results indicate significant potential the pathogens will be tested under field conditions based on Shapiro-Ilan et al. (2007). A variety of application and formulation approaches will be tested as well. Certain plant growth regulators have been shown to prevent leaf chlorosis elicited by black pecan aphid feeding. These plant growth regulators will be tested for efficacy in controlled field experiments to ascertain their practical application in pecan production systems. New chemical controls for stink bugs will be evaluated against existing controls to provide efficacy as well as residual activity data. Stink bug efficacy tests will be conducted against brown and green stink bugs. Pecan nuts on trees will be sprayed with insecticides and brought to the laboratory 1, 4, and 7 days after insecticide application. For each day after application that stink bugs are tested, one stink bug will be placed into a cup with one nut and mortality assessed at 24 and 48 hr. Objective 3. Integration of techniques at points of known positive interactions between factors. 3.1 Georgia, U.S.D.A. - Integration of legume intercrops to increase soil fertility and enhancement of biological control of pecan aphids by ladybeetles will be investigated in controlled field experiments to determine methods for attracting ladybeetles from the legume intercrops to the tree canopy and the planting density of cool and warm season intercrop plants that will increase the abundance of ladybeetles on the orchard floor. Application of lower amounts of commercial formulations of complete fertilizers will be investigated by improving the placement and timing of applications. Standard broadcast application of fertilizer will be compared to fertilizer: placed near the areas wetted by the irrigation system and fertilizer; placed in the herbicide strips; and, added to the planting clover in the cool season as a cover crop followed by the application of manures in the spring. The timing of the fertilizer application will be investigated to prevent rapid increases in leaf nitrogen levels that precede aphid outbreaks. A single spring application at the full rate will be compared to three monthly applications in the spring and early summer. The frequency of fungicide sprays for pecan scab can lead to increases in pecan aphid populations by suppressing aphidophagous fungi leading to an aphid outbreak. Eleven hours of leaf wetness triggers a pecan scab outbreak. Leaf wetness will be monitored in the experimental orchard and fungicides will be applied when the leaf wetness period exceeds 11 hours to reduce the frequency of fungicides and reduce control costs and enhance biological control of pecan aphids by entomopathogenic fungi. Trials will be conducted to compare the incidence of entomopathogenic fungi in pecan aphid populations from orchards with full season fungicide cover sprays and orchards with sprays applied on a timing schedule based on leaf wetness. We will also compare the incidence of entomopathogenic fungi in pecan aphid populations in pecan trees treated with various fungicides. Integrated approaches using both chemical insecticides and fungicides and microbial agents will be explored. Additionally integration of microbials with other orchard management practices such as cover cropping will be tested as well. Objective 4. Develop real-time Decision Aids for Delivery on the Internet. 4.1 Regional Research (All states and USDA) - All states and USDA will participate in cooperation with the Pecan ipmPIPE Producer Advisory Board and producers in the planning, development and delivery, in association with extension, of decision aids to improve adoption and use of IPM by stakeholders. This will include continuing to recruit and train producers cooperating in the current program as well as involvement in new efforts as they evolve. A number of orchards to represent different latitudes across pecan growing areas of the southeastern U.S. will be monitored with pecan nut casebearer traps and supplemented with nutlet counts to determine the need for and timing of insecticide sprays. Results will be compared to an available degree day model for model validation.

Measurement of Progress and Results

Outputs

  • The project will generate new data on insect monitoring methods, chemical and biological pest controls and the interactions that occur in the field between soil fertility maintenance and pest control methods.
  • New information will be generated on the seasonal occurrence of various arthropod pest populations and their associated beneficial insects and mites.
  • Concurrent collection of climatic information will be analyzed for possible correlations between population dynamics and climate.
  • New data on the efficacies of new control methods, the impact of the new control methods on the other insects and mites in the orchard, the interactions between the new methods and cultural methods, particularly, the maintenance of soil fertility with cover crops and commercial fertilizers will be generated by work of the new regional project.
  • Decision aids and IPM education materials will be delivered on the Pecan ipmPIPE Platform and traditional extension service activities. These extension components should lead to measurable and documented changes in the learning of new pest control methods by pecan growers. The extension components will incorporate all existing pest management knowledge in addition to the current new knowledge generated by the research components of the regional project.
  • Output 6: Discussion groups and a survey will be used as evaluation tools to determine how effectively the current and new information is being learned and used by pecan growers.

Outcomes or Projected Impacts

  • Pest control and fertilizer costs are increasing rapidly in comparison to other pecan production costs. The greatest impact of the proposed research work will be the development of lower costs pest control and soil fertility maintenance costs for pecan growers.
  • The new methods outlined in the proposed work will be compared with standard methods for efficacy against the pests and residual control after the application.
  • New chemical controls that are more effective and have a longer residual control period than the standard method should be readily used by pecan growers.
  • The released biological control agents may offer sustained control the pests for several seasons and have additional value to the pecan grower.
  • Reduced fertilizer rates or the application of split applications of fertilizer several times during the season may reduce sudden flushes in leaf nitrogen and prevent aphid and mite outbreaks.
  • Outcome/Impact 6: Cover crops and inter crops add nitrogen to the soil and enhance biological control of aphids; Outcome/Impact 7: Tracking information extracted from the Pecan ipmPIPE Platform will be analyzed to identify who was accessing what information, when and how much they growers were accessing, and then interpreted to determine probable effects on adoption of IPM; these results will be additionally informed by on-line surveys on the platform and independent surveys conducted in the various states; Outcome/Impact 8: Overall, we expect producers to be better informed, increase adoption of IPM including biocontrol, apply fewer and better timed treatments and thereby reduce operating costs, risk of resistance and harm to the environment.

Milestones

(0):estone 1.1 Design sampling methods for pecan weevil, pecan aphids, aphidophagous insects, pecan nut casebearer, Prionus root borers and pecan phylloxera that estimate insect density within ± 15% of the actual population size and a precision of 30-100% Sampling for pecan weevil, pecan aphids and pecan nut casebeaerer have nearly attained these goals and should be completed by 2011. Aphidophagous insect sampling should reach these marks by 2013 Phylloxerans and Prionus root borer sampling should be this accurate and precise by 2014 - 2015

(0):estone 1.2 Design damage assessment levels that estimate nut injury to the nearest 1-5% of the actual damage level. Pecan nut casebeaerer and pecan weevil nut injury varies with the size of the crop and this level of accuracy in the damage assessment should be attained by 2014 or 2015. Hickory shuckworm injury is already estimable within 1% but the actual damage will not be estimable without further research on the impact of injury on kernel quality. We may have an idea of this impact by 2015. Stink bug injury is fluorescent and is estimable by external examination with black light and this should hasten the attainment of this goal to 2012.

(0):estone 1.3 Develop forecasting models for pecan weevil, aphids and mites similar to the pecan nut casebearer forecasting model. Forecasting models for pecan weevil have to be developed from known relationships between crop size, cultivar, soil moisture (rainfall), and kernel phenology. Model development should be completed by 2013 with validation during 2014-2015 Pecan nut casebearer forecasting is already inuse across the region and is improved each season with results collected from over 200 locations region wide. Thid goal has been reached and will continue to improve through 2015. Pecan aphid population parameter estimates are well established in eastern and western locations of the U.S. A model is under development at Texas A&M and regional testing of the model should be completed by 2013. Mite population parameters a less known and modeling efforts are far behind the aphid work. 2015 would be the earliest time for completion of validation of any models for pecan leaf scorch mite and its predators.

(0):estone 2.1 Develop more effective control methods for pecan weevil and pecan aphids through field evaluations and insecticide resistance monitoring and concomitant evaluations for non-target effects of pesticides and biological controls. Insecticide resistance monitoring is in development for systemic insecticides such as imidacloprid as we are just now able to measure the concentration of this insecticide in the leaf. By 2013 a bioassay for systemic insecticides should be developed and in use to test aphids. Contact insecticides have bioassays in place for aphids, mites and pecan weevil. More effective biological controls for pecan weevil have been found in the previous regional research effort. These are insect pathogens and entomophillic nematodes. Testing requires several years since the life cycle of the weevil is 2-3 years long. 2015 is the earliest date that these controls will be used on commercial orchards Non-target effects of pecan insecticides are currently known for aphids and aphid predators and should be completed for phytoseiids by 2012 New pesticides are developed year by year depending on the innovation by the industry and registration processes. Typically two or three new pesticides are registered for use on tree nut crops (incl. pecans) and the dates that the process is complete is out of the control of research.

(0):estone 3.1 Conduct multi-factor field trials that compare the efficacy of insect control methods under varying conditions. The results will be completed in 2015 For objective 4 [Develop real-time decision aids for delivery on the internet] Milestone 4.1 Provide a central website for all pecan insect and mite related

Projected Participation

View Appendix E: Participation

Outreach Plan

Outreach - The current research work of the regional project will be reported in refereed publications of the Entomological Society of America, Georgia Entomological Society and other scientific journals. The pecan industry is fortunate to have a well-established network of state and regional grower associations that produce highly read and distributed, editor-refereed publications including The Pecan Grower, Pecan South, Proc. Southeastern Pecan Growers Association, Northern Nut Growers Journal and Proc. of the Western Pecan Growers Assoc. These associations also host annual meetings and field days that include educational sessions and equipment shows where the new control methods can be presented and demonstrated to the growers by the researchers or their extension counterparts. The information generated by the regional research project is also taken directly to the growers by extension specialist in all pecan producing areas of the U.S.

The current information will also be presented to pecan producers as a whole with previous research information and practical considerations by extension efforts by the technical committee members or their extension counterparts. The new and improved insect and mite control methods developed by the regional research will be implemented on commercial pecan orchards by extension efforts in five categories. First, traditional extension publications will be updated. Second, awareness development in the pecan growers will be improved by increasing the accessibility of the information nationally through ipmPIPE and locally though SAES and CES websites. Third, workshops will be held in major pecan producing counties and parishes with specific goals of learning how to: prepare the orchard for application of new methods (which intercrops or trap crops to plant, irrigation requirements, fertilizer applications, which cultivars to purchase); economic advantages of the new methods over the old methods that are being replaced; differences in timing of applications for new versus old methods (as examples, biocontrols take longer to reduce pest populations than insecticides but offer sustained control; or, insect growth regulator insecticides have to be applied earlier than contact insecticides) . Fourth, growers and researchers and extension specialists will have in-depth educational experiences through on-farm research. Fifth, the impact of the research and extension efforts will be determined by comparing the responses by growers to two surveys  one at the onset and one at the termination of the project. The allocation of pecan extension responsibilities differ between pecan-producing states. In some states, the pecan research and extension work is accomplished by one person. In other states, extension specialists and researchers have responsibilities in several crops including pecans. It is therefore, important that the new information generated by the regional research project be implemented under these different types of organization. The best way to accomplish this is to present the new methods in the context of the old methods, i.e., what has to be changed and what can remain the same with respect to the cultural practices in the orchard to make the newer methods successful and reap the financial and environmental benefits of their use. This level of organization is new to pecan production and may lead to better integration of pest control methods into overall orchard management.

Organization/Governance

Organization: The technical committee will have three officers - secretary, vice-chairman, and Chairman: A new secretary will be elected from the members of the technical committee each year to serve a three year term, the first year as Secretary, the second year as Vice Chairman and the third year as Chairman. The technical committee will meet one time per year to discuss research and plan new activities.

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