Nymphs of both Virginia creeper leafhopper (VCLH) and Western grape leafhopper (WGLH) are present and continue to emerge at our vineyard monitoring sites in both Mendocino and Lake Counties (Fig. 1).

Nymph emergence is further along in Mendocino County, where 76-92% of leafhopper eggs show signs of nymph emergence (Fig. 2B). Sites in Lake County are more variable, where leafhopper egg emergence currently ranges from 15-91% (Fig. 2A).

Sprays were applied for leafhoppers at the Hopland, Ukiah/Talmage and Big Valley 2 sites. Black arrows in Fig. 1 indicate approximate spray date. You'll notice a decline in nymph densities following the sprays at most sites.

Now is the time to be monitoring nymph populations in your vineyard. Leafhopper nymph identification guidelines are available here (video) and here (text version).

Due to the lack of biological control, effective early-season control of VCLH is critical. Based on monitoring, if control measures are needed, the optimum application period would be when the majority of the population is still in the younger nymphal stages before they molt into adults. This is especially important if you plan to spray with an oil. Depending on population levels at your site, a follow-up application may be required to impact nymphs that emerge after the spray. Consult your PCA for materials, rates and timing.

We are pausing the parasitoid release program for a few weeks since egg deposition is no longer taking place. We will resume the releases once the current nymphs begin to molt into adults and we start to see fresh eggs on the grape leaves again.