Grapes Insects Uncategorized

Grape Mealybug Update, July 23, 2018

Grape mealybugs are entering the second generation for the growing season.  First instar crawlers are hatching and moving out from under the bark and into the canopy.  

Here is a video of crawlers in an egg cluster from under the bark of a trunk:

Here is what the crawlers look like under 200X magnification:

1st instar on tap

The graphs in this post show the development of the population on the trunk (lines) and catches on double sided tape placed around the trunk and canes (pink bar).

The first graph  shows mealybug development without a Movento treatment.  If grapevine leafroll-associated virus-3 is present in the vineyard, crawlers (1st instar larvae) can feed on infected vines and move to healthy vines and transmit the virus.  There are reports that virus-carrying crawlers may also be carried on equipment or workers clothing or blown by wind.  (We haven’t tested this yet).

Mealybug without Movento

The second graph below shows population development when Movento is applied at the recommended timing, when the adult population peaks post bloom.  Numbers of all growth stage declined and there were no crawlers found on the tapes.

Mealybug with Movento

Foliar treatment with Clutch, Malathion, Kopa, Opal or Pure Spray Green Spray oil will help to knock down the population but will affect only crawlers that are exposed.  It is critical to get excellent coverage with these products because mealybugs are often on the undersurface of leaves and hidden in leaf axils or other hard to reach spots.  Movento is systemic and will move into tissues so when mealybugs feed, they will ingest the active ingredient.

Especially at this time while very mobile crawlers are present, if you have not treated for mealybug, try to organize vineyard work (hand or mechanical) so that you don’t move mealybugs from that block to a clean block.  Power wash equipment (hedgers, leaf removers, tractors) after being in blocks known to have mealybugs.

Thanks to Jordyn Domio and Daniel Walmsley for doing weekly counts and to Sud Poojari and Jessica Oppenlaender for photos and video.

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