Threecornered alfalfa hopper (TCAH) is commonly seen in Georgia peanut fields each year. This insect is highly mobile as an adult, and large numbers can very quickly move into and out of a field. The adults are easily identified by their triangular shape and bright green coloration, and they will flush up from the foliage as you walk through the field.
Adult and nymph TCAH feed on plant phloem, but it is the nymph stage that is thought to cause most of the damage. The nymphs create stem girdles by puncturing the plant’s vascular tissue with their needle-like mouth parts. The insects then feed on phloem that accumulates just above the girdle. The reduced transport of phloem to the roots and developing pods could result in decreased yield, though this has not been proven experimentally in Georgia. TCAH is one pest that is thought to prefer high moisture environments, but we have already had some reports of the insect in non-irrigated fields in 2015 in spite of the dry conditions in May.
TCAH nymphs are much more difficult to detect in the field than adults. They range in color from light tan to brown to green, and they are generally slow moving. Threecornered alfalfa hoppers are not hard to kill, but if and when to treat them is the real question. We are currently working to develop economic thresholds for the insect, but in the mean-time we will have to rely on past experience and our best guess when making management decisions. We do not want to be too aggressive with treating TCAH since the pyrethroids we use will eliminate natural enemies and can flare secondary pests.
Potato leafhopper is more sporadic in our peanut fields than threecornered alfalfa hopper, but the “hopper burn” that is caused by its feeding can be dramatic. The tips of leaves will turn bright yellow in a characteristic “v” shaped pattern. Very often, infestations go unnoticed until hopper burn is observed. The adult PLH is highly mobile and much smaller than the TCAH. When you visit a field that is showing hopper burn, it is very important that you verify that the pest is still present before recommending/making an insecticide application. Fortunately, PHL is easy to control, but unfortunately the pyrethroids we use can flare secondary pests.