Watch For Potato Leafhopper To Avoid Hopperbur

DR. RIC BESSIN

PRINCETON, KENTUCKY

Small insect pests often go unnoticed until their damage appears, and this is true with potato leafhopper. Potato leafhoppers 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-seeded alfalfa.  Spring-seeded alfalfa fields are more susceptible to injury by this pest because of the long period after seeding until the first cutting.  For this reason, producers should watch their spring-seeded fields closely and treat as necessary.

Potato leafhopper is a migratory insect that moves north on warm south winds from its overwintering sites in 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. But its arrival is dependent on active weather systems, which can carry it northward.

While potato leafhopper is a pest of alfalfa in general, it can be more problematic in spring-seeded alfalfa. Potato leafhopper is tiny and easily overlooked, but size has little to do with importance as a pest. Spring-seeded alfalfa needs to be monitored regularly for this pest until the first cutting. The extended 70 to 90 day growth period before first harvest allows time for damaging numbers of leafhopper numbers to build and damage stands. More frequent cutting of established alfalfa helps to manage potato leafhopper numbers. Significant numbers of leafhoppers often find their way into spring-seeded fields in spring with a rapid increase during June and a peak in early July, but usually disappear from Kentucky alfalfa fields in late July.

Damage

Potato leafhopper (PLH) 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.

Monitoring for Potato Leafhopper

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 information and treatment thresholds, read Potato Leafhoppers (ENTFACT-115). ∆

DR. RIC BESSIN: Entomology Extension Specialist, University of Kentucky