No abstract

Studies on effects of chemical control of the cotton aphid during the early season on (1) the growth and fruiting characteristics and yield of cotton, and (2) pest and natural enemy number and pest damage during the mid and late season, were conducted during the period from 1984 to 1989 in cotton fields in coastal areas of East China. Chemical control of the cotton aphid during early season does not affect the number of lateral bud, node, boll and summer boll produced per plant, nor does it decrease square sheds or increase pre-frost bloom rate and lint yield of cotton plants. Instead, chemical control during the early season reduces the number of natural enemies and increases the number of pests and amount of pest damage on cotton during the mid and late season.

Fungal leaf blight diseases caused by Cercospora carotae and Alternaria dauci occur annually on processing carrot in New York, with growers applying up to eight fungicide sprays to manage these diseases. An integrated pest management (IPM) program involving the use of a 25% disease incidence threshold to prompt the first fungicide application and timing subsequent sprays by monitoring for increases in disease severity and weather forecasts in conjunction with a 10- to 14-day spray interval was evaluated in grower fields in 1997 and 1998. The IPM plots, compared with the grower plots, required two to six fewer fungicide applications but showed no yield reduction. From 1999 to 2004, the IPM program was validated and the effect of crop rotation and carrot cultivar susceptibility also were assessed. Carrot plants growing in fields with 2-year or longer crop rotation intervals reached the 25% disease incidence threshold later in the season and required fewer fungicide applications. The less-susceptible carrot cultivars also reached the 25% disease incidence threshold later, required fewer fungicide applications, and were less severely diseased than more susceptible cultivars. Validation of the IPM program in New York showed that both fungal leaf blights can be managed effectively using a 25% incidence threshold to prompt the first fungicide spray and making the subsequent fungicide applications based on increases in disease severity, weather forecasts, and a 10- to 14-day spray interval.