2013 Annual Report
1a.Objectives (from AD-416):
1. Survey organic orchards on predator release practices
2. Develop methods to allow differentiation between released and naturally occurring predators
3. Develop methods to optimize release methods
4. Conduct laboratory trials to compare efficacy of reared and released species
1b.Approach (from AD-416):
Organic apple growers will be surveyed to determine extent to which insectary reared natural enemies are released as components of biological control programs in orchards. We will develop molecular methods allowing us to differentiate among field-collected predators originating from releases versus naturally occurring populations. Tests of release efficacy will be done by comparing pest and predator densities in areas of the orchard receiving releases and areas in which no releases are made. Field trials will be done to assess how release methods (numbers released, timing of releases, stages of predator released, method of release) influences efficacy. Laboratory trials will be done to confirm that insectary-reared predators feed and develop on target pests. Documents Trust with WA Tree Fruit Research Commission. Log 41879. Formerly 5352-22000-017-62T (6/10); 5352-22000-019-26T (1/11).
The work summarized in this progress report relates to objective number 1 of the Project Plan for 001-00D: 1. Develop new knowledge of the behavior, genetics, systematic, physiology, ecology, and biochemistry of the insect pests of apple, pear, and cherry, and their natural enemies, that will aid in the discovery, development, and application of management methods and technologies.
Through interviews and surveys we found that many organic orchardists manually apply purchased lacewing eggs glued to paper pieces, in order to release lacewings into trees to control pest aphids. This is a labor-intensive approach and of unproven value prompting evaluation of lacewings application using liquid carriers. More than 50% of lacewing eggs sprayed onto trees in liquid carriers was lost on impact with the trees. We found that the insectary-produced lacewing, Chrysoperla rufilabrus, showed feeding capacity similar to our native lacewing, Chrysopa nigricornis. C. rufilabrus will hatch at an appropriate temperature in March to allow for early and more valuable predation on aphids.
Experimental mass releases of predator mites proved unsuccessful in suppressing pest spider mites. Pesticide residues prevented predator mite establishment in one year and a high number of existing predators in other studies showed there to be no effect of addition of predators through augmentative releases. Large release experiments of both lacewing eggs (2011) and mites (2010-2012) showed no increase in predators and in the case of lacewing eggs, no released C. rufilabris were recovered likely due to predation of eggs by ants and other predators. The dominant predator mite found in 5 orchards was Amblydromella caudiglans, stimulating new studies on the value of this predator compared to the more common, Western predatory mite.