Extraction from soil of apterous Pemphigus populitransversus (Hemiptera: Pemphigidae) feeding on cruciferous vegetable roots

The poplar petiolegall aphid, Pemphigus populitransversus Riley (Hemiptera: Pemphigidae), is a gall-forming aphid attacking leaf petioles of Populus spp., its primary hosts. Its secondary hosts are the roots of cruciferous (Brassicaceae) plants, where it is also commonly known as the "cabbage root aphid." The apterous forms are destructive pests of cruciferous vegetables in many parts of the world. In our experiments, the root-feeding apterous forms were extracted from the soil using a Berlese funnel, which drives the aphids downward by using light and heat. The results show that a majority of apterous aphids (96.9%) were extracted from the soil in 2 h by using a 15-W light bulb in the Berlese funnels, whereas only 18.2% of aphids were extracted using a 25-W light bulb in a similar time period. The 25-W light bulb in the funnel generated too much heat (40-44 degrees C), which dried the soil too fast so that the aphids were unable to crawl downward to the collecting jars or killed the aphids directly. The advantages of using a Berlese funnel equipped with a 15-W light bulb as the light and heat source for sampling and extraction of the root feeding aphids include a uniform handling of each sample, less time spent, extraction of many samples at the same time, and storage of the aphids in containers for later counting in the laboratory. This technique seems to also be useful for extracting other mobile, small soil-dwelling arthropods.