Santa Rosa, Calif., (August 2, 2017) – In the spring, grapevine nurseries will deliver tens of thousands of vines for new developments and vineyard blocks scheduled to be replanted in Sonoma County. Vines will also arrive to replace plants lost to Pierce’s disease and those that were pulled because of leafroll or red blotch disease. For new and redevelopments, sig- ni cant resources and time were invested months before the delivery date to insure that on the day of planting the site is prepared, the irrigation system functions, stakes or plant markers are in and labor is available. Given these “times” one more item should be added to that long list. Vines should be inspected for vine mealybug by your crew before the vines are planted and if the pest is found, the Agricultural Commissioner o ce should be informed.
Vine mealybug (Planococcus cus) was rst discovered in Coachella Valley in 1994 and in 1998 it was found in
vineyards in Kern and Fresno Counties. Within the next 5 years it was in 16 counties and infested plant mate- rial was one of the contributing factors to that rapid spread. Although the movement of vine mealybug on nursery stock is far less of an issue now than it was prior to 2003, in the long run, it pays to spend time looking at vines while they are in the ats just to be certain the pest is not seen. Once vine mealybug becomes established in a block it must be controlled every year with an IPM program that utilizes insecticides and eventually mating disruption plus diligent monitoring to evaluate e cacy.
Vine mealybug is spread naturally by wind and birds and by farming practices that move the immature insects to other areas inside the block and to adjacent blocks. ere are 3 to 4 overlapping generations in the North Coast and pest populations increase throughout the grow-
ing season. By midsummer, all stages of the insect can be found on canes, clusters, leaves, petioles as well as under the bark on trunks and cordons. As they feed, they excrete copious amounts of honeydew. Vineyard equipment and clothing is easily contaminated when it contacts sticky plant parts that contain young immature insects (crawlers) which are less than 1 mm long.
Grapevine nurseries take measures to prevent dormant and green benchgra s from becoming infested with vine mealybugs. e CDFA Nursery Stock Pest Cleanliness Standards requires nursery stock to be free from vine mealybug. Nurseries can be in compliance of the stan- dards of cleanliness requirements by using the Vine Mealybug Trapping and Survey Protocol provided by CDFA. In the protocol, adult vine mealybug males are monitored with the use of sticky traps which contain a lure loaded with a synthetic form of that insect’s sex pheromone.
In lieu of conducting the trapping and survey protocol, nurseries may voluntarily immerse dormant grape cuttings and rootings in hot water following a protocol provided by CDFA. e county Agricultural Commissioner’s sta must approve of the dipping equipment and ensure the recording thermometers are calibrated. Most nurseries routinely hot water dip and do so under a compliance agreement with their Agricultural Commissioner’s o ce.
Green gra ed vines can’t be immersed in hot water and there is no protocol currently available for treating these vines. Nurseries apply insec- ticides and take other measures to prevent vines from becoming infested during the production process. e wax that is used to protect the gra union also protects insects that get under the wax.
Given that vine mealybugs continue to spread within grape growing regions in California, vineyards are at risk of becoming infested. Infested plants from nurseries are rare, but it happens. Taking the time to inspect them on-site is critical. Budgeting labor hours to inspect vines before planting may reduce farming costs in the future if infested vines are not planted – and your neighbor does the same.
By Rhonda Smith, UC Cooperative Extension Farm Advisor