An Insect and Disease Scouting Guide for Protecting Yield from Emergence to Harvest
Effective pest management starts at emergence, and each growth stage brings different threats to the crop, both insects and diseases.
Scouting is key to managing pests before the crop and yield suffer. Knowing the area’s history, properly staging the plant and regularly walking the field are the first steps to effective scouting. Common approaches are to walk the field in a Z, W or diamond pattern to ensure the edges and interior of the field are inspected, stopping frequently to check the leaves, stems, ears/pods and roots for symptoms.
“The first thing you’ll want to do is go throughout the field and take a look at your overall uniformity of emergence,” said Jonathan Rotz, Pioneer strategic account manager. “The flat-bottom trowel or flat-bottomed spade is a great way to actually diagnose what’s going on below the soil surface.”
When to Scout for Key Corn Pests
Each pest requires its own scouting technique as they affect the plant differently at various stages of plant development, which is generally divided into vegetative and reproductive stages.
Common pests during the early vegetative phase are corn rootworm larvae and black cutworm. Corn rootworm larvae feed on the plants’ developing roots, threatening its nutrient supply. Black cutworm chew holes in the leaves and cut into the stalk, threatening the plant’s growing point.
European corn borer is an emerging insect threat around the V6 growth stage because they tunnel into stalks, ear shanks and ears, disrupting water and nutrient transport in the plant, which increases the risk of stalk lodging and ear drop. Gray leaf spot and northern corn leaf blight also come into play around this stage and continue through the reproductive stages, causing reduced photosynthesis from defoliation.
After silks appear, staging moves to reproductive and is based on the kernels of the primary ear until physiological maturity.
At this point, corn rootworm adults can cause silk clipping, which can inhibit pollination and harm yields. Stalk rots and ear rots are also possible as the ears develop to physiological maturity.
Critical Soybean Pests and Their Timing
Starting in the first two months after planting soybeans, soybean cyst nematode can damage the plants’ roots, enabling crop diseases such as sudden death syndrome or red crown rot to infect the plant.
Two months before the plant reaches its maximum height, soybean aphids and white mold become a threat to yield. Soybean aphids feed on all parts of the plant, causing leaf distortion, yellowing, and stunted growth, as well as producing honeydew that promotes sooty mold growth and reduces photosynthesis. White mold grows through dying plant tissue, causing tissue rot, rapid wilting, death of the upper part of the plant and potentially premature death of the entire plant.
After the flowers begin to bloom, sudden death syndrome and red crown rot start to appear in the field, even though they infect the plants early in the season through the roots. After foliar symptoms appear, it is a matter of mitigating risks in future seasons.
After noticing unusual activity in the field, growers should use available resources from local Extension or agronomists to identify the issue and act quickly.
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