Time to Scout for Corn and Soybean Aphids

Categories: GROWING, CORN, SOYBEANS
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Once pollination is complete, corn and soybean insect concerns return. Aphids are 1 such insect capable of causing late-season damage. With piercing, sucking mouthparts, they feed on plant sap. Aphids excrete sugar-rich honeydew that can cover the aboveground portion of plants. This honeydew can promote a sooty mold that interferes with plant photosynthesis.

Corn control

In recent years, aphid populations have grown in corn at somewhat alarming rates. While the impact of aphids on soybean yield potential is well-documented, the yield effect on corn is not quite as clear.

No threshold for aphids found in pollinated corn is currently defined. However, limited data from Iowa State University Extension suggests that when there are 500 or more aphids per plant in 80% of the field, an insecticide application will be beneficial.

Soybean management
University Extension specialists and industry agronomists agree it’s important to continue scouting for soybean aphids through the mid-R6 growth phase. Aphid feeding can damage soybean plants over time. This damage results in reduced photosynthesis, and eventually lower yield as plants abort pods and seeds. Viral diseases are also transmitted as feeding continues.



When temperatures are in the high 70s and low 80s, aphid populations can double every 2 to 3 days. Thresholds may vary depending on growth stage, soil moisture, and heat or drought stress. Soybeans in the 2.0 relative maturity group planted in May and early June generally reach R6.5 in early September, so continue scouting through the end of August.


​​​​​​​Source: Purdue University Extension

Scout several areas of the field for increasing aphid activity. Populations of 250 aphids per plant, or more than 80% of the field infested, justifies treatment. This allows about 1 week before reaching the economic injury level. Endigo® ZC insecticide combines 3 industry-leading technologies for quick knockdown and extended residual control of key foliar insect pests, including soybean aphids. The chart below shows how soybean aphid population growth compares to insect pressure per plant over time.

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Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.

Photos are either the property of Syngenta or used under agreement.

Syngenta hereby disclaims liability for third-party websites.


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