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Title: TRI-TROPHIC INTERACTIONS AND PREDATION RATES IN CHRYSOPERLA SPP. ATTACKING THE SILVERLEAF WHITEFLY

Author
item LEGASPI, JESUSA - TEXAS AGRIC. EXPT. STN.
item Nordlund, Donald
item LEGASPI, BENJAMIN - TEXAS AGRIC. EXPT. STN.

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The silverleaf whitefly is an important pest of many crops in the U.S. and caused about $500 million in crop loss in 1991. Because it is difficult to control with insecticides, many scientists are studying the use of insect predators, which feed on the whitefly. Among the most effective predators of whiteflies are green lacewings, which are sold commercially. Previous studies showed that lacewings are better at controlling whiteflies on some plants than on others. We performed several experiments to find some of the reasons for this to learn how to best use lacewings for whitefly control. In our first experiment, we found that whiteflies avoid laying their eggs on leaves where we had previously placed lacewings. Apparently, whiteflies try to avoid the lacewings to prevent their young from being eaten. The longer the lacewings were on the leaves, the fewer the eggs that were layed by the whiteflies after the lacewings were removed. We also wanted to see how different plants affected the lacewings by feeding them whiteflies raised on cucumbers, cantaloupes, poinsettias and lima beans. We found that whiteflies raised on cucumbers and cantaloupes caused the lacewings to grow faster, live longer and weigh more than did those from poinsettia and lima beans. Poinsettias and lima beans may contain harmful plant products consumed by the whiteflies and passed on to the lacewings or produce whiteflies of low nutritional value to the lacewings. Finally we compared two lacewing species to find if one ate more whiteflies than the other but found that they both ate 25 - 75 whiteflies per day. This study shows that lacewings can be more effective in controlling whiteflies and other pests in some host plants than in others.

Technical Abstract: We investigated tri-trophic interactions among the host plant, the silverleaf whitefly (SLWF), Bemisia argentifolii, and the predatory lacewings Chrysoperla rufilabris and C. carnea. To test if the lacewings produce whitefly oviposition deterrents, lacewing larvae were placed on host plant leaves for durations of 2, 3, or 4-d. Control leaves had no predators. B. argentifolii females avoided ovipositing on leaves on which C. rufilabris larvae were previously located; this tendency increased with increasing exposure time of the predators. To investigate the effects of host plant on SLWF as prey, SLWF immatures were reared on poinsettia, cucumber, cantaloupe and lima bean and fed to C. rufilabris.. We measured the effects of host plant on body weight, developmental duration and survivorship of the lacewing. Lacewings that fed SLWF reared on cucumbers and cantaloupes developed more rapidly, showed increased survivorship, and weighed more as newly-emerged adults than those raised on poinsettia and lima bean which did not survive to the pupal stage. SLWF reared on poinsettia or lima bean may have been nutritionally inadequate for C. rufilabris development or the whiteflies may have accumulated plant compounds detrimental to the development of the lacewings. Finally, we compared predation rates between C. rufilabris and C. carnea. There was little difference, although C. carnea may consume significantly more whiteflies during certain intervals. Both species generally consumed between 25 and 75 whiteflies daily.