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Insects in Pulse Crops

pea aphid
Pea Aphids Detected in Pulse Crops 2010
by: Janet Knodel, Extension Entomologist, NDSU and Kevin Wanner, Extension Entomologist, MSU

Low levels of pea aphids have been detected in peas grown in the north central and northwest regions of North Dakota. This is the most common insect pest found in field pea. They are small, about 1/8+ inch long, and pale green.

Last year, producers were surprised by pea aphid in their pea fields and lost up to 10 bu/acre. So, it is wise to scout pea fields for aphids when 50-75% of the peas are flowering by using either a sweep net or examining the number of aphids per plant tip. Take 180-degree sweeps using a 15-inch sweep net or check at least five 8-inch plant tips from four different locations in the field. Population estimates should be calculated by averaging counts taken from four separate areas of the field.

Economic Thresholds:
Economic thresholds may vary depending on the value of the crops and cost of control, as well as impacts of precipitation and heat stress. The economic threshold in peas at $5.71 per bushel and average control cost of $6.73-$9.25/acre is 2 to 3 aphids per 8-inch plant tips, or 9 to 12 aphids per sweep (or 90 to 120 aphids per 10 sweeps) at flowering. If the economic threshold is exceeded, a single application of insecticide when 50% of plants have produced some young pods will protect the crop against yield loss and be cost-effective. Cultivars of peas may also vary in their tolerance to feeding by pea aphids. Thus, economic injury levels may differ between cultivars. The economic thresholds presented above were developed using "Century" field peas.

Aphid feeding on peas in the flowering and early pod stage can result in lower yields due to less seed formation and smaller seed size. Protein content and other quality issues do not appear to be affected.

Research in Manitoba has shown that insecticides applied when pods first form protects pea yield better than earlier or later applications. Control at the early pod stage provides best protection through the pod formation and elongation stages, which are very sensitive to aphid damage.

For insecticides registered in North Dakota for pea aphid control, consult the 2010 Field Crop Insect Management Guide at:

Janet Knodel, Extension Entomologist
contact me

Kevin Wanner, Extension Entomologist
contact me
Montana State University

The following material is published by NDSU Extension Service. It is for the 2009 crop year only.

2009 Field Crop Insect Management Guide

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