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The march of the mealybugs (and scales)

We have been monitoring for movement of crawlers of mealybugs and scales in commercial vineyards in Niagara with a history of mealybug and scale since early April of 2019.

The crew started finding crawlers on double sided tape wrapped around the heads and canes of vines 2 weeks ago but crawlers were few and far between. 

Clear double sided tape wrapped around the head of a grapevine trunk.  Waxy egg masses of mealybug are visible where the bark was peeled off.
Double sided tape wrapped around the head of a grapevine trunk
3 orange first instar crawlers on double sided tape.  Crawlers are approximately 0.2 mm wide and 8 mm long.
3 first instar mealybug crawlers on double sided tape on trunk head
Yellowish brown oval scale, 0.5 mm long
First instar crawler of scale (0.4 mm long) on double sided tape on trunk head

This week the crew started looking on canes, especially under the bark that peels up when canes are bent to be tied. They found LOTS of crawlers. 

Several tiny pinkish orange mealybug crawlers on a cane from which the bark has been peeled.
Mealybug crawlers under peeled bark on grape cane, May 7, 2019
A small oval pinkish orange crawler circled in red in the centre of a cane with the bark peeled back to expose it.
Scale crawler on cane
Small and medium sized crawlers of scale on a grapevine trunk near the head.
Scale crawlers at the head of a trunk. Smaller insects are earlier instars.

Spring sprays for mealybugs and scales

These insects are easily detected on canes (with a hand lens if you need reading glasses) so head out the vineyard and see if they are active. The next few days would be the optimum time to apply a spray to try to kill off these exposed crawlers and reduce the mealybug population.  Sprays are more effective on younger instars. Once mealybugs return to the trunk under the bark to lay eggs, only Movento will reach them and you’ll have missed this first generation of insects because Movento won’t move down into the trunk and affect the second generation until after bloom.   

To ensure penetration of the spray under those flaps of bark, use a high volume of water. This would be an excellent time to use a recycling sprayer.  Products registered for control of mealybug include Vegol Crop Oil (20 L/1000 L water), malathion (880 mL/1000 L water), Kopa or Opal insecticidal soaps (10 L/1000 L water) and Clutch (140-210 g/ha).  These products will also control scale crawlers.

This timing has not been recommended in the past in Ontario (or in Publication 360, but it will be in future editions) because we did not have a good feeling for the timing for this early season treatment, but the time is NOW!

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