The warm weather has pushed not only grapevine development, but also associated pests.

Mealybugs and Scales

Mealybugs and scales have progressed to third instar to adult growth stage and are making their way back under the bark on the trunks.  This follows the development we’ve seen in the past relative to vine development.  We should start to see first instars around pea size berry. Because Movento takes some time to get to where the first instars are feeding, the optimum timing for the first Movento spray is post-bloom.

4 adult female mealybugs, light pink in colour on the wood under the bark of a trunk
Adult female grape mealybugs under trunk bark
(Photo credit: Raquel Schoeneberg, OMAFRA)
Cluster of 3 dark brown (adult) and 3 medium brown (ntermediate) scales under bark on a trunk
Adult Lecanium Scales under trunk bark. Dark brown scales are adults; medium brown scales are intermediates (Photo credit Raquel Schoeneberg)

Erineum mites

Erineum mites have been active and causing significant damage in some vineyards with entire leaves affected.  Colonies of mites live inside the blisters (erinea) formed by their feeding on the lower surfaces. The blisters contain masses of enlarged tangled leaf hairs.  Inside the galls, the females lay eggs which hatch to produce nymphs.  When mature, nymphs (crawlers) emerge from the galls and move to new tissue and initiate new galls. Several generations occur every year with new galls developing nearest the growing shoot tip.  While the symptoms are striking in appearance, the insect can usually be controlled by routine early season sprays with Sulphur.  Oils have also been reported to have some impact on spread of erineum mite.

canning Electron Micrograph of Eriophoid type mite like erineum mite
Green leaf with raised bumps where erinea from erineum mite feeding.
Raised “blisters” on upper surface of grape leaf are symptomatic of erinea produced by Erineum mite (Photo credit Prestyn Sider, Niagara Pest Monitoring Club)
Entire lower surface of leaf covered in dense felty white hairs of erinea. Erineum mites are developing beneath the hairs inside erinea.
(Photo credit Prestyn Sider, Niagara Pest Monitoring Club)

Downy and Powdery Mildew

Warm, humid weather and overcast skies are optimal conditions for powdery and downy mildew development.  Once vines reach the 5-6 leaf stage, there is enough foliage to be able to intercept the spores so infection can be initiated.  First lesions of downy mildew have been detected and powdery mildew is likely to show up soon as well.    Look for yellowish spots on the upper surface with white fluffy sporulation underneath for downy mildew.  The first powdery mildew lesions are most likely to be on the underside of leaves

Yellowish greasy spot on upper leaf surface.
Yellowish “oilspot” with irregular indistinct margins on upper leaf surface is a symptom of down mildew.
Yellowish lesion on undersurface of leaf with some fluffy white sporulation of the downy mildew fungus beginning
Underside of an oilspot with sporulation of downy mildew fungus beginning.
Pale whitish grey area in middle of the undersurface of a leaf.
Primary lesion of powdery mildew resulting from an infection from overwintering ascospores.

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