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Project description

The Development of a Marking Method for Assessing Field Survival and Dispersal of Aphytis melinus and Other Augmentative Biological Control Agents. (99FE024)
Program UC IPM competitive research grants program
J.G. Morse, Entomology, UC Riverside
R.F. Luck, Entomology, UC Riverside
Host/habitat Citrus
Pest California Red Scale Aonidiella aurantii; Yellow Scale Aonidiella citrina
Discipline Entomology
Aphytis melinus; parasitoids
Applied Field Ecology
Start year (duration)  1999 (Two Years)
Objectives Develop a method for marking and identifying field-released parasitoids.

Develop field collection and sampling methods to recapture marked natural enemies.

Test suitability of marking and collection methods for evaluating survival and dispersal of insectary reared parasitoids following field release.

Final report We have adapted and implemented a method to mark Aphytis melinus, a hymenopterous parasitoid of California red scale and yellow scale, with immunuglobulin proteins. To apply the marker, we expose the parasitoids to a fog of an aqueous solution of the protein. Detection of the marker is accomplished by means of enzyme-linked-immunosorbent-assay (ELISA). According to our tests, the marking method has negligible effects on survival and activity of the insects. We also developed traps to catch large numbers of A. melinus in the field (citrus orchards) with minimal labor. Traps consist of red scale-infested lemons as baits and oil covered yellow cards. The red scale-infested fruit evidentially emit volatiles attracting female Aphytis which subsequently become trapped in the oil on the yellow cards. With the goal of using the above marking and trapping methods for evaluation of parasitoid field survival and dispersal relating those to laboratory-assessed quality traits, we had to develop additional procedures: to estimate the numbers of live parasitoids in large batches (up to 100,000 wasps) as delivered by insectaries, we first separate live and dead parasitoids by releasing them in the center of an arena. Heating up the release area to 40°C (104°F) stimulates the live insects to move into the cooler parts of the arena whereas the dead ones remain in the warm center. Numbers are estimated by spreading the insects out on a background of contrasting color and taking digital photographs. Using image-scanning computer software, we automatically count the numbers of objects (insects) in the picture. We also developed tests to assess walking and flight activity of the parasitoids. The developed techniques can be used to obtain indicators of biological control of red scale and yellow scale by Aphytis. The trapping method can be used to evaluate the activity and population of Aphytis in specific orchards. Live-dead separation, counting, and flight- and walking-tests can be used to evaluate the quality of biological control agents received from the insectaries. We are in the process of testing the mark-recapture methods to evaluate field survival and dispersal of insectary reared Aphytis and how these attributes are related to the laboratory assessed flight and walking performance, and the size of the parasitoids.

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