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Functional Response of Selected Cotton Arthropod Predators to Bollworm Eggs in the Laboratory

Ram B. Shrestha, Megha N. Parajulee, and Carlos Blanco


The functional response study of the ten most common arthropod predators of cotton bollworm (Helicoverpa zea) eggs was conducted in the laboratory. Crab spider (Misumenops spp.) and assassin bug (Zelus renardii) did not consume any bollworm eggs under laboratory conditions and the scymnus lady beetle (Scymnus loewii) consumed very few (avg. 0.5 eggs per beetle) bollworm eggs in a 24-hour period. Functional response was measured by offering varying densities of bollworm eggs for each predator species and the functional response was recorded for 24 hours. Soft-winged flower beetle (Collops spp.), minute pirate bug (Orius spp.), hooded beetle (Notoxus spp.) and damsel bug (Nabis spp.) showed Type-I response, while lady beetle (Hippodamia convergens) adult, lady beetle larva, and green lacewing larva (Chrysoperla spp.) showed Type-II response; big-eyed bug adult (Geocoris spp.) showed Type-III functional response. Among the predators with Type-I functional response, the Collops beetle had the highest slope. Lady beetle larva had the highest handling time (0.185 h) followed by lady beetle adult (0.14 h) and green lacewing larva (0.08 h). Lady beetle adult and green lacewing larva showed a significantly higher attack rate or searching rate compared to lady beetle larva.

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Document last modified 04/27/04