Grape mealybug eggs laid last fall overwintered under the bark of trunks, hatched to produce crawlers that emerged in early spring and progressed through their phases of development. Last week the majority of the population was adult females. Fresh egg clusters were detected this week.
Time for control measures
This means that if mealybugs have been a problem in your vineyard, a Movento spray will be required in the next week. Efficacy of Movento is maximized when tank mixed with a non-ionic surfactant or horticultural oil at 0.2% v/v (2 L/1000 L water).
Spray may NOT be necessary
We have been tracking mealybug in some vineyards that were treated with Movento in previous seasons and the trend seems to be that if Movento was used to the full rate per year of 920 mL/ha for one or two years, the mealybug population drops drastically and you can get away without a Movento spray for at least a year. However, rather than assume this is the case in your vineyard, it’s best to peel back the bark on trunks and canes of 10 vines to check for adult females and eggs to confirm no mealybugs are detected. The adults are about 3 mm long and covered in white flaky scales. The eggs are oval and dark orange and are encased in a cottony cluster.
Optimize pollinator safety
If mowing row middles or borders is imminent, do this before applying Movento to reduce exposure of pollinators visiting any blossoms in cover crops. Take measures to minimize drift of Movento outside the vineyard and spray in the evening when bees are less likely to be active.
Possibility of spreading mealybug?
It is important to keep in mind that the first instar crawlers (the ones that hatch from the eggs) are the most motile and also the best leafroll virus vectors. The crawlers are tiny and can hitchhike undetected on workers’ clothing when they’re doing things like leaf removal or shoot positioning. There is speculation that they can be blown from one block to another by airblast sprayers or pneumatic leaf removers so it’s best to use this equipment before or after crawlers are present. The presence of first instars will be monitored by the crew and posted in the blog. To minimize the possibility of moving mealybug crawlers, always start work (manual or mechanical) in vineyards where you know mealybugs are not present and then progress to those where they are.