ABSTRACT

A total of 7,200 ears of corn were sampled in mid to late July 2002 from 146 corn fields in 29 counties in Virginia to determine Helicoverpa zea larval population levels - and to make predictions regarding sequential infestation levels in cotton, soybean and peanut. An average of 45 to 75% of the ears sampled were infested with larvae or showed signs of damage, depending on region, which was up considerably from 2001 levels. Predictions were that growers could expect moderate to high infestation levels. Potential for insecticide resistance was evaluated using vials pretreated with either cypermethrin at 5 or 10-µg rates, spinosad at a 15-µg rate, or untreated (control). A total of 1,147 moths were captured live in mesh pheromone traps from June 25 through September 5 from two locations and placed into pretreated vials. An average of 5.0, 1.7, and 5.5% survived the 5 and 10-µg cypermethrin and 15-µg spinosad rates, respectively, which was similar to results from 2001, but lower compared with results from 2000. Heliothine eggs were collected from commercial cotton fields on 20 different dates from July 24 to August 30 and subjected to the Agdia Hel-ID egg testing procedure to determine the species. Heliothis virescens comprised about 29 to 80% of the total tested in July, dropped to about 5% in mid August, and increased to about 14% towards the end of August. A total of 618 Heliothine larvae were collected from peanut, soybean and cotton fields from August 9 to September 13 and identified to species in the laboratory. Over all sample dates, only 5.0 and 4.0% collected from peanut and soybean, respectively, were H. virescens, with the remainder being H. zea. However, the proportion of H. virescens varied from 0 to 11%. These data and the insights they provided were extended to growers and used to improve in-season worm management practices.