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Scout for Pea Aphids in Pulse Crops (07/25/19)

Economic populations of pea aphids are being reported in NC and NW areas of ND.

Economic populations of pea aphids are being reported ient.11n NC and NW areas of ND. Pea aphids are small, about ⅛ inch long and pale to dark green with reddish eyes. 

Life Cycle:  Pea aphids have multiple generations per year and overwinter as eggs in alfalfa, clover or vetch. In the spring, nymphs hatch from eggs and appear similar to the wingless adult but smaller. Nymphs molt four times and mature into adults in 10 to 14 days. Pea aphids can reproduce rapidly when temperatures are around 65 F and relative humidity is near 80 percent. Infestations can originate from local alfalfa fields or migrate in from the Southern states.

Crop Damage:  Pea aphids have piercing-sucking mouthparts, went.12hich suck the juices from plants. Pea aphids are effective vectors of viral diseases. For example, pea seed-borne mosaic virus (PSbMV) is an economically damaging viral pathogen of field pea that can cause significant losses in seed yield and quality, especially when infections occur before or during flowering. Consult the NDSU Extension publication PP1704 Pea Seed-borne Mosaic Virus (PSbMV) in Field Peas and Lentils, for more information.

Pulse crops are especially susceptible from the flowering to early pod stage and during drought stress. An economic infestation 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 by aphid feeding.

Aphid populations are usually kept low naturally by heavy rains or beneficial insects including parasitoid wasps and predators, such as ladybird beetles and lacewings. Early seeding also can reduce damage caused by pea aphids.

Pest Management:  Scouting for aphids in pulse crops is conducted using a sweep net or examining the number of aphids per plant tip when 50 to 75 percent of the crop is flowering. Take 180-degree sweeps using a 15-inch sweep net or check at least five 8-inch plant tips from five different locations in the field. Population estimates should be calculated by averaging counts taken from five separate areas of the field.

If the economic threshold is exceeded, a single application of insecticide at 50 percent of plants in young pods stage will protect the crop against yield loss. If an insecticide application is necessary during flowering, spray when bee foraging is minimal, preferably during the evening hours (after 8 p.m.).

For more information, consult the NDSU Extension publication E1877 Pulse Crop Insect Diagnostic Series: Field Pea, Lentil and Chickpea, and E1143 North Dakota Field Crop Insect Management Guide.

Threshold for Chickpea:  There is no recommended economic threshold for aphids in chickpea. To prevent virus infection, select varieties bred for virus resistance.

Threshold for Field Pea:  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 are not impacted by pea aphid feeding injury. During early reproductive growth stages of field pea, an insecticide treatment is recommended when an average of 5 to 19 pea aphids per plant or 3 to 12 pea aphids per 180-degree sweeps with a 15-inch diameter sweep net.

Threshold for Lentil:  Insecticide treatment for pea aphid control should be considered (1) when an economic threshold of 30 to 40 aphids are collected per 180-degree sweep with a 15-inch diameter sweep net, (2) when few natural enemies are present, and (3) when aphid numbers do not decline over a 2-day period.

Janet J. Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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