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.

	Average # of VCLH nymphs/leaf
Location	May 24	May 31	June 7	June 14	June 21
Talmage 1	1.9	9.4	9.7	0.6	3.5
Hopland 1	0.1	2.6	3.5	0.6	0.4
McDowell Valley	0.3	6.7	8.9	5.3	2.2

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/

Virginia creeper leafhopper and Western grape leafhopper peak egg laying 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). On June 7^th we observed nymphs between 1^st and 5^th instar stage, with the majority of the population between 3^rd and 4^th stage. Nymph development will continue in the coming weeks, so now is the time to be monitoring nymph populations in your vineyards.

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.

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).

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

	Average # of VCLH nymphs/leaf
Location	May 24	May 31	June 7
Talmage 1	1.9	9.4	9.7
Hopland 1	0.1	2.6	3.5
McDowell Valley	0.3	6.7	8.9

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/

Virginia creeper leafhopper and Western grape leafhopper continued laying eggs on basal leaves (see Fig. 1 & 2), although peak egg laying has passed. 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 for May 24 & 31). We are observing nymphs between 1^st and 3^rd stage instars, an ideal target stage when spraying with an oil. Nymph emergence and development will continue in the coming weeks, so now is the time to be monitoring nymph populations in your vineyards.

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. 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.

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

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).

Table 1. Average number of Virginia creeper leafhopper nymphs per leaf at three locations in Mendocino County on May 24 and 31.

	Average # of VCLH nymphs/leaf
Location	May 24	May 31
Talmage 1	1.9	9.4
Hopland 1	0.1	2.6
McDowell Valley	0.3	6.7

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/

VCLH nymphs began to emerge on May 14^th, 2018

This season we will once again be monitoring the development of Virginia creeper leafhopper, VCLH, (Erythroneura ziczac) and Western grape leafhopper, WGLH, (Erythroneura elegantula) populations in Mendocino County Chardonnay vineyards. The monitoring efforts this year will be limited to three different locations in Mendocino County where known populations of Virginia creeper leafhopper occur (Hopland, McDowell Valley and Talmage). We plan to provide information regarding egg deposition and nymph development of these leafhopper species at key times this growing season.

Virginia creeper leafhopper and Western grape leafhopper continued laying eggs on basal leaves (see Figures 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 for May 24). Nymph emergence will continue to increase in the coming weeks. We will monitor the number of nymphs per leaf going forward this growing season.

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. 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.

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