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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #72791
Title: FIELD PERSISTENCE OF A MULTIPLE NUCLEAR POLYHEDROSIS VIRUS OF THE CELERY LOOPER, ANAGRAPH FALCIFERA, ON SWEET CORN SILKS

Author
item PINGEL, RANDALL - IOWA STATE UNIVERSITY
item LEWIS, LESLIE

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: The corn earworm is one of the most destructive insects of vegetable crops in the United States. Currently, the earworm is controlled on sweet corn with chemical insecticides. Problems associated with chemical insecticide use have led to the search for alternative forms of management of the corn earworm. An insect virus has been identified for control of the corn earworm. There are however, factors that limit the use of viruses in insect management. One is the inactivation of the virus by sunlight. Previous research has shown rapid inactivation of insect viruses by sunlight in the field. The lack of persistence would lead to more frequent application and/or a considerable increase in the initial spray concentration to provide adequate pest control; thus, the use of viruses as microbial insecticides would not be economical. We measured the persistence on sweet corn silks of a recently discovered insect virus alone and when formulated with starch and the sugar, sucrose, as a possibl protectant. Our results indicated that the nonformulated virus maintained residual activity at approximately 80% after nine days, and there was no increase in the persistence of the formulated virus. The high degree of persistence was unexpected, but very encouraging relative to management of insect pests of the corn ear. Our results show that the virus can be used as an alternative to chemical insecticides. Use of the virus will substantially reduce the amount of chemical insecticides necessary to produce sweet corn.

Technical Abstract: One factor limiting the use of nuclear polyhedrosis viruses as microbial insecticides is their inactivation by sunlight. To protect viruses from sunlight and prolong their activity, various materials have been added to viral sprays to increase the efficacy of field applications. We measured the residual activity of Anagraph falcifera multiple polyhedrosis virus (AfMNPV) alone and when added to a starch-based adjuvent. The treatments were sprayed on sweet corn silks in the field; the silks were collected on the day of application and 1, 3, 6, and 9 days after application. The viral residuals retrieved from the silks were fed to neonate corn earworms, Helicoverpa zea, using a modified droplet method, and subsequent mortality was recorded. Results showed no significant difference between the virus and virus+starch treatments: percentage of original activity was maintained for at least three days (?90%) and after nine days was 78 and 64%, respectively.