Tuesday, May 28, 2024

Economically Important Arthropod Pests

worm pest of peanutsInsects and mites can cause severe economic loss, but not every field will be infested with damaging populations every year. Pest species also vary from year to year and field to field within a year.

Understanding the risk factors that contribute to pest outbreaks and weekly scouting are the foundations of successful insect management. Below are some of the most common and economically important arthropod pests, conditions that favor their development and scouting tips.

⇒ Thrips: Found in most fields, but early planting, conventional tillage, single-row pattern and no at-plant insecticide increase the injury risk.

– Scouting Tips: Look for adult and immature thrips in the first three to four weeks after emergence. Immature thrips are usually found in folded terminal leaflets.

⇒ Lesser Cornstalk Borer: Found in hot, dry, well-drained sandy soils and open crop canopy.

– Scouting Tips: Look for wilted stems and silk tubes, remove plants and check tap root, pods and stems for feeding injury and larvae. Moths are a good sign of LCB infestation. Plants in a “skip” or at the ends of rows with bare soil around them will usually be attacked first.

⇒ Three Cornered Alfalfa Hopper: Found in most fields, but densities are highest in adequate soil moisture. Populations increase as the summer progresses.

– Scouting Tips: Adults fly when disturbed and are easily collected in sweep nets. Nymphs, responsible for much of the injury, are difficult to see. Beat sheet sampling or careful examination of vines is required to find nymphs. For treatment decisions, consider the relative abundance of adults, nymphs and stem injury and the risk of flaring secondary pests.

corn rootworm⇒ Southern Corn Rootworm: In heavy-textured soils with good moisture. Larvae cannot survive in dry soil.

– Scouting Tips: Larvae live entirely below ground. Dig adjacent to peanut rows or remove plants to examine pods for damage and check the soil for larvae.

⇒ Potato Leafhopper: Found sporadically in peanut fields. Infestations often begin along field margins.

– Scouting Tips: Adults fly when disturbed; nymphs are similar in appearance to adults but cannot fly. Look for hopperburn (V-shaped yellowing of leaflet tips), especially near field edges. Hopperburn will persist after the insects have left the field, so it is important to determine if infestations are active before making a treatment decision.

⇒ Velvetbean Caterpillar: Does not overwinter in Georgia. The first moths are often detected in South Georgia in June, but infestations do not typically reach threshold until later in the summer.

– Scouting Tips: Vigorously shake vines to dislodge the insects onto the ground or a beat sheet. Sampling three feet of row at 10 locations is sufficient for a typical 40- to 80-acre field. All caterpillars should be identified, counted and their size noted.

⇒ Two Spotted Spider Mite: Found when conditions are hot and dry. Non-irrigated corners of irrigated fields are often severely injured while the irrigated portion has few or no mites. Field margins, especially near dirt roads, are usually infested first. Mowing infested weedy vegetation adjacent to fields can result in mites migrating to the crop in large numbers.

– Scouting Tips: Check field edges. Small patches of yellowing peanuts are an early indication of infestations. At low densities, mites are difficult to see and are usually found on the lower surface of leaves. Early detection is important. PG

Information from Mark Abney, University of Georgia Extension and research entomologist.

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