Monitoring efforts during the week of May 14th showed the first emergence of VCLH nymphs for the season (see Table 1/Figure 1 for # VCLH nymphs per leaf). The numbers of nymphs decreased on the week of June 11th as the three vineyards we are monitoring were sprayed around that time. On June 21st we observed cast skins for both VCLH and WGLH, signaling adult emergence and the start of the next generation egg laying. The nymph population is on the decline again due to second-generation nymphs molting into adults. Generations of VCLH are now overlapping; with viable VCLH eggs being observed across all sites in the field while conducting the nymph counts. The leafhopper adults will begin moving higher up into the canopy to oviposit their eggs and thus we will be monitoring nodes 4-6 now.
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, follow-up applications may be required depending on previous treatments and leafhopper population thresholds, so it is important to continue to monitor for nymphs. Consult your PCA for materials, rates and timing.
Table 1. Average number of Virginia creeper leafhopper nymphs per leaf at three locations in Mendocino County, 2018.
| Average # of VCLH nymphs/leaf |
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Location | May 24 | May 31 | June 7 | June 14 | June 21 | June 28 | July 5 | July 12 | July 19 |
Talmage 1 | 1.9 | 9.4 | 9.7 | 0.6 | 3.5 | 4.8 | 9.1 | 5.1 | 0.9 |
Hopland 1 | 0.1 | 2.6 | 3.5 | 0.6 | 0.4 | 0.9 | 1.5 | 0.2 | 0.5 |
McDowell Valley | 0.3 | 6.7 | 8.9 | 5.3 | 2.2 | 2.5 | 3.5 | 0.4 | 0.1 |
Figure 1. Average number of Virginia creeper leafhopper nymphs per leaf at three locations in Mendocino County, 2018.
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/