Submitted to: Annual Southern Conservation Tillage Conference for Sustainable Agriculture
Publication Type: Proceedings
Publication Acceptance Date: 5/3/1995
Publication Date: N/A
Interpretive Summary: The use of conservation tillage to produce cotton is increasing in the southeastern USA. Changing tillage systems may impact the number of insect pests and their natural enemies in a cotton field. In this study, we monitored the populations of cotton bollworm, tobacco budworm, and some natural enemies in cotton grown with different conservation tillage systems. We found that highest populations of tobacco budworm and cotton bollworm occurred in July. Their numbers were reduced in August because a tiny wasp that kills the pest eggs was very active. Throughout the season, the most abundant natural enemies of the two pest insects were bigeyed bugs, lady beetles, and ants. Ant populations were highest in the tillage system that did not use between-row mechanical cultivation for weed control. In that tillage system, pest egg populations were reduced compared to the tillage systems that had mechanical between-row cultivation. These results will help scientists develop better management techniques for pest insect control in conservation tillage cotton.
Technical Abstract: Populations of the tobacco budworm, Heliothis virescens (F.), the cotton bollworm, Helicoverpa zea (Boddie), and their natural enemies were monitored 27 April - 8 September 1993 and 21 April - 1 September 1994 in crimson clover (Trifolium incarnatum L.) and a subsequent conservation tillage cotton (Gossypium hirsutum L.) crop. Treatments included winter cover (crimson clover and fallow) and midrow weed control method (herbicide-glyphosate and V-blade cultivator). Thrips were counted weekly 18 May - 17 June 1994. Predaceous arthropods (mostly the bigeyed bug, Geocoris spp.) and parasitoids (Hymenoptera:Braconidae) were very active against H. zea and H. virescens populations in crimson clover during May. Pest population densities remained low through June in cotton. The peak in tobacco budworm/cotton bollworm population densities occurred during July. Bigeyed bugs, lady beetles, and ants were the most abundant predators. Densities of ants were highest in plots that had a clover cover and were not cultivated, and tobacco budworm/cotton bollworm egg reductions were detected in noncultivated plots. Egg parasitism by Trichogramma spp. was important in helping to reduce bollworm populations during August. Thrips numbers were low and highly variable among treatments with no clear patterns.