Edamame are soybeans harvested at a physiologically immature (R6) stage as a specialty food item for fresh and processed (frozen) markets. The soybean aphid, Aphis glycines Matsumura, is a newly introduced insect pest of soybeans in North America. This field study was to provide baseline information on the impact of A. glycines on the edamame soybean. This study determined the population growth rate of A. glycines on two edamame soybean cultivars, ‘Butterbeans’ and ‘Envy,’ at two planting dates during 2004 and 2005 in Nebraska. Aphid population growth was significantly higher on 'Butterbeans' than on 'Envy' for the first planting date in both 2004 and 2005 seasons, whereas the second planting date only had significant higher soybean infestations on 'Butterbeans' during the 2005 season. The infestation difference was the greatest on plants at the late reproductive growth stages, R5 and R6, in 2005. Aphid’s infestation at 'Butterbeans' growth stages in 2005 was significantly different for the first and second planting dates. The aphids were higher on plants at the R6 and R5 growth stages than the other stages for first and second planting dates, respectively. However, ‘Envy’ growth stages in 2005 did not exhibit significantly different average aphid infestation during the first and second planting dates. This study revealed that soybean aphid population growth on edamame soybeans is affected by the planting date, season, and cultivar choice.
Key words: Growth stages, cultivars, infestation, planting date
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