Author
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HENNEBERRY, THOMAS |
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JECH, LYNN |
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BURKE, REBECCA |
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Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/1/1996 Publication Date: N/A Citation: N/A Interpretive Summary: The pink bollworm remains an economic pest of cotton in the southwesternUnited States and worldwide. Insecticides are the principal means of control. No biological agent is currently used to augment indigenous natural enemies and a biological component in management systems is urgently needed to reduce insecticide use. We treated soil in the laboratory with the entomopathogenic nematodes, Steinernema riobravis and S. carpocapsae, and found that low percentage of pink bollworm adults that emerged from pupae placed on the treated soil were infected. Higher percentages of larvae released on nematode treated soil were infected and higher percentages of larvae buried in the soil were infected with S. riobravis but high percentages of larvae were infected by S. Carpocapsae, when larvae were released on the soil surface. In the filed, S. riobravis persisted longer (over 60 days) than S. carpocapsae (15 days) as measured by soil sample bioassays. Both nematode species have potential for biological control of pink bollworm in cotton Technical Abstract: Pink bollworm, Pectinophora gossypiella (Saunders), (PBW) adults were 16.7-34.0% and 20.7-26.7% infected from pupae on soil treated with Steinernema carpocapsae (Weiser) or S. riobravis Cabanillas, Poinar and Raulston. In moist soil larval mortalities were 91.9% on the day 0 and 5.1% on day 35 following treatment for larvae on soil surfaces treated with hS. riobravis and 50.0 and 7.0%, respectively, for larvae buried 1.7 cm in the soil. Mortalities for larvae on S. carpocapsae soil surfaces were 90.5% on day 0 and 38.5% on day 35 after treatment. Mortality of larvae buried 1.7 cm in the soil was 31.0% on day 0 and 3.0% on day 35 after treatment. When soil treated with S. riobravis was allowed to dry between larval releases on soil surfaces or burial in soil, but wetted on the day of larval exposure, mortalities ranged from 37.3-97.8% for the soil surface and 62-84% for buried larvae. Also, S. riobravis parasitized higher percentages of buried PBW larvae than S. carpocapsae but less than S. carpocapsae for larvae released on the soil surface. Under field conditions, larval mortalities from plots treated with S. riobravis (5 per cm2) were 50% on day 0 and 2.5% on day 90. Mortalities with S. carpocapsae (5 per cm2) were 32.5, 15.3, 5.3 and 2.5, respectively, for day 0, 1, 7, and 15 following treatment at 25 nematodes per cm2 of soil surface, PBW larval mortalities ranged from 100% on day 0 to 7.5% on day 63 with S. riobravis and 92.5% on day 0 to 5% on day 7 following treatment with S. carpocapsae |
