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Vol. 16, No. 16
Article 5 of 9
September 1, 2006
Soybean Aphid found in Northeast Missouri
By Wayne Bailey
Clinton Meinhardt, MU extension agronomists in northeast Missouri, has
found soybean aphid in several producer fields. Soybean most at risk
are double crop or late planted beans in the early reproductive stages
of growth. Most fields in the area are in the late reproductive stages
of R5 or R6 and should have reduced risk from this pest. Cool
temperatures will favor the growth of aphid infestations, but
beneficial insects will help reduce numbers. This insect is capable of
very rapid reproduction with a new generation produced ever 5-10 days
depending on temperatures. Adults give birth to living young with all
sizes of aphids sucking juices from soybean plants. The economic
threshold at which treatment is justified is an average of 250 or more
aphids per plant during growth stages of R1 (flowering) to R5 (pod
fill). There is some data from Canada that suggest yields can be
protected even when beans are sprayed with an insecticide in growth
stage R6. Most more northern states have not found this to be the case
in their states. The greatest benefit from control of this pest is
realized at the early stages of reproductive growth (R1-R3) and
diminishes as the plants develop through the later reproductive
stages. Several insecticides are labeled and effective at reducing
pest numbers. Due to the late date of the soybean aphid infestations
in northeast Missouri, the soybean aphid is unlikely to be a major
economic pest in most soybean fields this season. Although numbers are
low in most fields, producers are encouraged to scout for the aphids
in order to determine pest status in their fields.
Wayne Bailey
Entomology
573-882-2838
573-864-9905
