Adult leafhopper emergence has begun

Virginia creeper leafhopper and Western grape leafhopper peak egg laying from the overwintering adults has passed (Fig. 1 & 2). Monitoring efforts during the week of May 14^th showed the first emergence of VCLH nymphs for the season (see Table 1 for # VCLH nymphs per leaf). The numbers of nymphs decreased on June 14^th as the three vineyards we are monitoring were sprayed. As of June 21^st, the nymph population is on the rise again due to nymphs that emerged from viable eggs after sprays were applied. On June 21^st we observed cast skins for both VCLH and WGLH, signaling adult emergence and the start of the next generation egg laying. The leafhopper adults will begin moving higher up into the canopy to oviposit their eggs.

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 the emergence of adults. 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.

Figure 1. Average number of Virginia creeper leafhopper eggs per leaf at three locations in Mendocino County. Egg monitoring stopped at the end of May. 

Figure 2. Average number of Western grape leafhopper eggs per leaf at three locations in Mendocino County (Note: the y-axis scale is different from previous graph). Egg monitoring stopped at the end of May. 

Table 1. Average number of Virginia creeper leafhopper nymphs per leaf at three locations in Mendocino County.

Ryan Keiffer and Lucia Varela, UCCE, are conducting the 2018 leafhopper monitoring. For more information, please visit the Areawide Virginia Creeper Leafhopper website: http://ucanr.edu/sites/vclh/