Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2006
Publication Date: June 1, 2006
Citation: Legaspi, J.C., Simmons, A.M., Legaspi,Jr, B.C. 2006. Prey preference by Delphastus catalinae (Coleoptera: Coccinellidae) on Bemisia argentifolii (Homoptera: Aleyrodidae): effects of host plant and prey stages.. Florida Entomologist. 89(2). Interpretive Summary: A ladybeetle, Delphastus catalinae, is a predator of an important pest, the silverleaf whitefly, Bemisia argentifolii. We studied the preference of this predator in attacking the whitefly in major crops such as cotton and vegetables as well as ornamental plants. Leaf cuttings from the following plants were tested: cotton, tomato, cowpea, collard greens, and Hibiscus. In a separate experiment, we determined whether this ladybeetle prefers certain immature stages of the whitefly prey. The prey stages tested in tomato leaf cuttings were eggs, small prey (first to third stage nymphs) and large prey (fourth stage nymphs to pupae). We found that the beetle preferred to feed on whitefly in cotton, followed by whitefly in collards, cowpea, tomato, and Hibiscus. The difference in prey preference by the predator may be due to attraction to certain plant chemicals released by the leaf cuttings. We also found that D. catalinae preferred to feed on silverleaf whitefly eggs and small nymphs compared to large nymphs and pupae. Our findings suggest that this species of ladybeetle may be most effective as a biological control agent when the cotton plants are young and/or when whitefly eggs are most abundant.
Technical Abstract: Host plant and insect host stage preference were studied in the predator Delphastus catalinae (Horn) (= pusillus) (Coleoptera: Coccinellidae) feeding on the silverleaf whitefly (Bemisia argentifolii Bellows and Perring) (Homoptera: Aleyrodidae). To study host plant preference, immature whitefly prey were presented simultaneously to starved predator adults on leaf cuttings of five different host plants: cotton (Gossypium hirsutum L.), tomato (Lycopersicon esculentum Mill.), Hibiscus (Hibiscus rosa-sinensis L.), cowpea (Vigna unguiculata [L.] Walp.) and collard greens (Brassica oleracea L.). Percentage predation over 24 h was significantly highest on cotton, followed in approximate order by collards, cowpea and tomato, and lowest on Hibiscus. Different predation rates may have been caused by differential attraction to volatile secondary compounds released by the leaf cuttings. Host stage preference was studied by presenting individual predators with equal numbers of prey (200 per replicate) in three aggregate life stages: eggs, small nymphs (1st to 3rd instars) and large nymphs (4th to pupae). Significantly higher numbers of eggs were consumed in a 24-h predation period, compared to small or large nymphs. Findings suggest that Delphastus catalinae may be most effective on early-season cotton or immediately after whitefly infestation when eggs are predominant.