Potato leafhoppers (PLH) often go unnoticed until their characteristic damage to alfalfa begins to appear in early summer. Potato leafhopper is tiny and non-descript, hence, it is easy to overlook. It is the key insect pest of second and third cutting alfalfa, as well as spring-seededalfalfa. The extended 70 to 90 day growth period before first harvest in spring seedings allows time for damaging numbers of leafhopper numbers to build and damage stands.
Significant numbers of leafhoppers often find their way into spring-seeded fields with a rapid increase during June and a peak in early July. Leafhoppers usually disappear from Kentucky alfalfa fields in late July. More frequent cutting of established alfalfa helps to manage potato leafhopper numbers.
Potato leafhopper is a migratory insect that moves north on warm winds from the Gulf States each spring. It generally arrives in May and their numbers will begin to increase rapidly during June to a peak in early July. Potato leafhopper is tiny and easily overlooked, but size has little to do with importance as a pest. Potato leafhopper can impact alfalfa in several ways. Insertion of their piecing sucking mouthparts to feed on sap physically damages vascular tissues of stems and leaves, and it blocks the phloem. This causes a characteristic symptom called hopperburn and results from the accumulation of photosynthates in leaves near the blockage. It begins as a V-shaped wedge of yellow extending from about the middle of the leaf to the tip.
This damage can result in stunted growth, premature leaf-drop, reduced root carbohydrate reserves, and drastic reductions in protein content of hay. PLH can reduce yields up to 25%, as well as lower crude protein, vitamin A, carotene, calcium, phosphorus, and digestible dry matter content.
Regular monitoring of spring-seeded fields alerts growers to potentially destructive potato leafhopper populations before they damage fields. Fields are sampled with a 15-inch diameter sweep net. Five sets of 20 sweeps are taken from randomly selected areas representing the entire field. These leafhopper numbers, coupled with the average plant stem height, is used to determine if a leafhopper treatment is needed. For more info, read UK publication ENTFACTS-115.
~ Ric Bessin, from Kentucky Pest News, June 2022.
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