Project Summaries

11-844VA  Project Manager: P. F. O'Leary


D. Ames Herbert, Virginia Polytechnic Institute and State University


    1. To assess potential pyrethroid resistance in bollworm using the adult vial test (AVT) system.
    2. To evaluate the effectiveness against bollworm and costs associated with double-insect-toxin (Bollgard II and WideStrike) cotton varieties.
    3. To evaluate conventional (non-Bt, non-Roundup Ready) cotton varieties for yield performance, and to weigh costs (including seed, herbicide, and insecticide) versus lint value.
    4. To evaluate the effectiveness of selected insecticides against the bollworm/budworm complex.

Objective 1 found that the mean bollworm survival rate of 37.1% in our 2012 adult vial tests was the highest that we have seen in Virginia since resistance monitoring began back in 2003.  Some "peak" survival rates reached 58%.

In Objective 2, Test 1, yields were comparable between conventional and double-gene insect-resistant cotton varieties when two bollworm sprays were applied to conventional cotton (increasing conventional cotton yields by 183 lb lint per acre).  Similar to previous research findings, double-gene insect-resistant cotton varieties that received one insecticide spray targeting bollworm usually had a slight yield boost from the application; the average yield increase in 2012 was 65 lb lint per acre.  In Test 2, bollworm damage reached 40% in unsprayed cotton.  We found that even with two sprays, conventional varieties sustained 2.5 to 12.5% bollworm damage.  Twice-sprayed plots had an average yield increase of 142 lb lint per acre.

In Objective 3, large replicated strip trials with three conventional varieties were conducted on four cotton producers' farms.  We scouted these locations and advised the grower when to apply insecticides targeting bollworm.  As a result, bollworm damage was low, often less than 1%.  Yields varied across locations, but were similar among varieties within each location.

From Objective 4 we learned that (at the rates evaluated) a single application of Belt was not as effective as single applications of Besiege, Prevathon, or Radiant in reducing worm-induced boll damage, nor was it as effective as two applications of Baythroid, Karate, or Brigade.  Yields, however, were statistically similar among all treatments.


Project Year: 2012

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