Management of Aphids is Brassica Seed Crops with Selective Insecticides

Abstract

Replicated studies were conducted to examine aphid distribution and insecticidal control in a commercial cauliflower seed crop in 2001, and in large plots at the Yuma Agricultural Center in 2003. Results were generally consistent in both studies. The primary aphid species found colonizing pre-blooming crops were cabbage aphids, turnip aphids, and green peach aphids. During the bloom period (March-April), the population was almost exclusively cabbage aphid feeding on seed pods and extensions. During the pre-bloom growth period, green peach aphids tended to colonize plants slightly earlier and were found primarily on the older frame leaves low on the plant. In most cases, male and female plants were colonized to the same extent. Cabbage and turnip aphids did not appear to have a clear preference between older and younger leaves, and appeared to colonize males and females equally. Once the plant began to bloom and set seed, cabbage aphid was the primary species (>90%) found feeding on developing seed pods in both tests. These aphid populations were very susceptible to contact insecticides and quickly knocked down by both Capture and MSR. Of the selective, bee safe products, Pirimor provided the most consistent residual aphid control. Assail and Fulfill worked well against aphids on foliage, but did not provide comparable control on seed pods. Aphid densities were extremely high in the untreated check and resulted in almost complete loss of the crop in these plots. Seed yields were not taken due to heavy losses to Sclerotinia and bird damage.