Potato Leafhoppers on Hops

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

I usually do not get the chance to look at many hop fields, as only a few farms have them, but they are becoming a bit more common in the last 10 years (Fig. 1). Visiting two farms with hops I saw marginal leaf damage (Fig. 2) on some leaves (found some thrips there) and then marginal leaf scorch on others (Fig. 3). When looking on the underside of the leaf-scorched leaves, I found many potato leafhopper, Empoasca fabae, nymphs (no adults) (Fig. 4) on one farm and only a few on the other.


Figures 1 & 2. Hops vine and hops leaf with the start of hopper/thrips damage

Potato leafhoppers prefer warm, dry conditions and are commonplace in southern states where they overwinter; leafhoppers do not overwinter in our area. Potato leafhoppers (PLH) move into our area via storm systems from the south. PLH are generally seen in late April or early May, but are arriving on average in our area 7-10 days earlier than just 20-30 years ago. Females lay 2-4 eggs per day in the leaf stems or veins of hops. In 7 to 10 days nymphs emerge. Nymphs undergo five instars and reach maturity in about 2 weeks. The newly emerged nymph is nearly colorless with red spots that fade. Nymphs then become yellow, finally changing to pale green in the third and later instars. There are 3-4 generations each summer. Leafhoppers are capable of very rapid population increases so scouting is important to control the pest to avoid damage to hops. Alfalfa and a few other forage legumes are the primary hosts for the potato leafhopper and once the first cutting of the forage is done, PLH will move into other susceptible crops such as potato and hops.

Damage: The most obvious symptom of potato leafhopper feeding is hopper burn. Hopper burn is the yellowing of the leaf margin (Fig. 3). This damage is followed by leaf curling and necrosis. Hopper burn occurs because potato leafhoppers feed by sucking the juices out of leaf veins and blocking the veins with a toxin in their saliva.


Figure 3. Leaves with severe hopper burn.

Monitoring and Management: Because potato leafhoppers can have very rapid population surges, it is important to scout and control them before major damage can occur. While there is no agreed upon threshold for leafhoppers in hops, most recommendations have a threshold at 2-3 PLH per leaf. Fields should be scouted weekly by checking the undersides of 5-10 leaves per 10–20 plants. If the average number of leafhoppers per leaf is at or above the threshold, then a control is needed. Because hops are a newer crop in our area states may differ in what they allow to be used, so be sure to check the label to see what your state will allow to be applied to hops for PLH control. In general, neonicotinoids, pyrethroids, or spinosyns could be used. Organic growers could use spinosad or pyrethrins that are OMRI approved for potato leafhopper management. If PLH are more of a consistent problem for you one suggestion is to plant red clover in drive rows (do not mow) as potato leafhoppers prefer to feed on the red clover than hops.


Figure 4. Potato leafhopper nymphs on hop leaf