Location: Fruit and Nut Research2012 Annual Report
1a. Objectives (from AD-416):
1. Develop alternative control strategies for the pecan weevil: (1.1) Determine the efficacy of biocontrol agents such as entomopathogenic nematodes (Steinernema and Heterorhabditis spp.) and entomopathogenic fungi (Hypocreales), and (1.2) investigate the basic biology and ecology of these agents to enhance efficacy. (1.3) Investigate improved methods of production, formulation, and delivery of these biological control agents, and integrate optimum biocontrol tactics with other management strategies. 2: Develop alternative control strategies for black pecan aphids through (2.1) assessment of pecan susceptibility (foliar damage ratings, aphid development, and aphid mortality), (2.2) use of plant growth regulators, and (2.3) microbial control agents including Beauveria, Isaria or Metarhizium spp. 3: Develop alternative control strategies for key peach pests (plum curculio, peachtree borers, and stink bugs) via (3.1) reduced-risk insecticides (such as thiamethoxam, flonicamid, and novaluron), (3.2) mating disruption, and (3.3) entomopathogenic nematodes.
1b. Approach (from AD-416):
Suppression of pecan weevil will focus on developing microbial control tactics including multi-stage entomopathogen applications, enhanced entomopathogen persistence through the use of cover crops, and synergism via combinations of entomopathogens and chemical insecticides. Additionally, pertinent basic studies on entomopathogens will be addressed. Management strategies for the black pecan aphid will use a long term approach to screen pecan for low aphid susceptibility (for use in pecan breeding), whereas, a short term approach will use plant growth regulators and microbial control. Suppression of key peach pests via reduced-risk insecticides, mating disruption, and entomopathogenic nematodes will be examined.
3. Progress Report:
Novel strategies for controlling a key pecan pest, pecan weevil, with microbial control agents were investigated as were new methods of applying beneficial fungi (e.g., with a compost amendment) and suppression using a bacteria-based bio-insecticide. Additionally, experiments measured the efficacy of entomopathogenic nematodes in suppressing key peach pests (e.g., plum curculio) and the most virulent agents were defined. These biocontrol approaches are promising for use against pecan weevil as well as key peach pests; grower adoption of the tactics has been initiated and has potential for expansion. Furthermore, fundamental research was conducted to explore dispersal mechanisms in beneficial nematode host-finding behavior, and stabilization of beneficial biocontrol traits. Novel methods of insect host and beneficial nematode production were investigated resulting in an issued patent on a mechanized insect separation system; the insects are used for mass production of nematode biopesticides. Continued research progress was made screening pecan germplasm for resistance to the black pecan aphid along with determining that plant growth regulators, used against the black pecan aphid, have no appreciable impact on the subsequent year’s return bloom of pecan. Insecticide assays identified compounds that show activity against both stink bugs and plum curculio. Further research regarding mating disruption for management of the lesser peach tree borer shows potential for managing this serious peach pest without insecticides.
1. Protecting pecan foliage from Black Pecan Aphids with plant growth bioregulators. Maintaining healthy pecan foliage is critical to the economic viability of producing and selling pecan nuts. ARS researchers at Byron, GA, found that treating pecan foliage with certain plant growth bioregulators (e.g., gibberellic acid) improves canopy health by lessening the negative impact of chlorophyll degradation from feeding by the black pecan aphid. Application of these plant growth regulators also increases season-long photosynthesis by retaining foliage longer into the autumn. Additionally, return bloom is not affected, and there appears to be little or no negative impact on beneficial insects. This new management tool is beginning to be adopted by growers and the approach is applicable to other crops experiencing pests that elicit leaf chlorosis through feeding.
2. Stabilization of beneficial traits enhances effectiveness of biological control. Safe alternatives to chemical insecticides are needed because of environmental and regulatory concerns. Biological control (the use of predators, parasitoids, or pathogens for pest suppression) is a viable option; however, during mass production biological control agents can lose beneficial traits, such as virulence and reproductive capacity, that result in the organism being less effective in pest suppression. ARS researchers at Byron, GA, and colleagues at Brigham Young University and Rutgers University, discovered that beneficial trait loss can be deterred through selection of homozygous inbred lines. These inbred lines are then used to mass produce high quality biological control agents. This inbred line technology has now been adopted by three commercial companies that produce insect-killing nematodes.
Shapiro Ilan, D.I., Bruck, D.J., Lacey, L.A. 2012. Principles of epizootiology and microbial control. In: Vega, F., Kaya, H.K., editors. Insect Pathology. 2nd edition. San Diego, CA:Elsevier. 29-72.