Location: Fruit and Nut Research2011 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 cover crop) and long-term suppression using entomopathogenic nematodes. Additionally, experiments measured the efficacy of entomopathogenic nematodes in suppressing key peach pests (e.g., lesser peachtree borer and plum curculio). 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. Additionally fundamental research was conducted to discover mechanisms of beneficial nematode host-finding behavior, determine the genetic basis of beneficial trait changes, and develop improved methods for biopesticide production. Research progress was made screening pecan germplasm for resistance to the black pecan aphid along with obtaining a better understanding of how plant growth regulators affect both black pecan aphid development and nut production. Progress regarding stink bug control has been made and shows that only certain pyrethroid insecticides provide better control than many other insecticides against the brown stink bug. Reduced-risk insecticides alone did not provide sufficient control but were beneficial when tank-mixed with other insecticides. Mating disruption for management of the lesser peach tree borer shows potential for managing this serious peach pest without insecticides.
1. Plant growth regulators improve health of pecan foliage. Maintaining healthy pecan foliage is critical to the economic viability of producing and selling pecan nuts. ARS researchers at Byron, GA have shown that treating pecan foliage with certain plant growth regulators improves canopy health by lessening the negative impact of chlorophyll degradation from feeding by the black pecan aphid. Application of some plant growth regulators also increases season-long photosynthesis by keeping leaves on the tree longer in the fall. Negative impacts against beneficial insects are not known. It is likely that these results are directly applicable to other crops, e.g., wheat, that have a similar pest problem.
2. Enhancing biological control through stabilization of beneficial traits. Due to environmental and regulatory concerns, safe alternatives to chemical insecticides are needed. Biological control (the use of predators, parasitoids, or pathogens for pest suppression) is often a viable option. However, during mass production biological control agents can lose beneficial traits such as virulence and reproductive capacity thereby making the organisms less effective in pest suppression. The basis for the trait deterioration phenomenon must be elucidated and methodology to overcome the problem must be developed. ARS scientists at Byron, GA and colleagues at Brigham Young University described the genetic basis for trait loss in entomopathogenic (insect-killing) nematodes and discovered that the problem is primarily due to inbreeding. The results indicate that trait deterioration can be deterred through the selection of homozygous breeding lines; thus, biological control efficacy can be enhanced.
Shapiro Ilan, D.I., Reilly, C.C., Hotchkiss, M.W. 2011. Comparative impact of artificial selection for fungicide resistance on Beauveria bassiana and Metarhizium brunncum. Environmental Entomology. 40:59-65.