grape phylloxera
Beginner
Scientific Name
Daktulosphaira vitifoliae
Identification
Eggs
- New eggs are oval, bright yellow approximately 0.4mm long and 0.2mm wide
- Prior to hatching, the eggs turn dark yellow with 2 visible red eye spots at one end
- Emerging nymphs are similar in size to the egg
- Progress through 4 developmental states before reaching the adult stage
- On the leaves, young adults are bright yellow to orange becoming brown with age
- On the roots they are pale green, light brown or orange
- Both forms are wingless and oval, 0.7mm to 1.0mm long and about 0.5mm wide
- The winged adult female, emerging from the soil in late summer and early fall, is orange with a grey-black head and thorax with two pairs of lightly veined wings
- green or red fleshy galls, 6–20 mm in diameter on undersurface of leaves and tendrils.
Often Confused With
Erineum mite injury – smooth blisters on the upper side of the leaf with dense white hairs on lower surface
Grape tumid gallmaker – smooth rounded galls on leaves, shoot tips, rachises
Period of Activity
First galls develop at 3-5 leaves. New galls continue to be produced on young leaves with successive generations of crawlers.
Scouting Notes
Monitoring of the leaf feeding cycle of grape phylloxera depends on timely visual observations. Galls begin appearing in mid-May, usually as one or two galls on the first to third new expanding leaves. When galls are first noticed, they should be sliced open with a razor daily until the eggs have started to hatch. Only then, when the tiny crawlers are active and moving are they susceptible to an insecticide application. Later in the season the generations of active crawlers are non-synchronous, and insecticides have little effect on the overall infestation.
Threshold
On very susceptible cultivars, especially on young plantings, apply treatments at development of first galls in the spring. In blocks with histories of infestation, the first insecticide should be applied when crawlers first appear from the galls as monitored by above process. Repeat applications may be required if new galls are observed on newly expanding leaves 14 to 21 days after first treatment.
Advanced
Scientific Name
Daktulsphaira vitifoliae
Identification
Eggs
- new eggs are oval, bright yellow approximately 0.4mm long and 0.2mm wide
- prior to hatching, the eggs turn dark yellow with 2 visible red eye spots at one end
- emerging nymphs are similar in size to the egg
- progress through 4 developmental states before reaching the adult stage
- on the leaves, young adults are bright yellow to orange becoming brown with age
- on the roots they are pale green, light brown or orange
- both forms are wingless and oval, 0.7mm to 1.0mm long and about 0.5mm wide
- the winged adult female, emerging from the soil in late summer and early fall, is orange with a grey-black head and thorax with two pairs of lightly veined wings
- green or red fleshy galls, 6–20 mm in diameter on undersurface of leaves and tendrils
Often Confused With
Erineum mite injury – smooth blisters on the upper side of the leaf with dense white hairs on lower surface
Grape tumid gallmaker – smooth rounded galls on leaves, shoot tips, rachises
Biology
There are two forms of phylloxera: one that creates galls on the roots and another that affects leaves. Although the two forms behave differently, both belong to the same species. All Vitis vinifera and French hybrid cultivars are susceptible to injury by the root-galling form and are recommended to be grafted onto phylloxera-tolerant rootstocks in Ontario. V. labruscana cultivars are considered tolerant to the root form of phylloxera; however, recent research demonstrated that root infestations on these cultivars can result in reduced vine vigour. The foliar form of phylloxera does cause significant injury on V. vinifera; however, many French hybrid and North American cultivars can sustain extensive foliar damage.
The wingless crawler stage (nymphal) of phylloxera comes out of the ground as soon as it warms up (just post bud break) and crawls to a new shoot up to the growing point. The nymph begins feeding via the upper surface of a young unexpanded leaf. As the leaf expands, a leaf gall develops around each phylloxera, forming a hollow pea-sized growth on the undersurface of the leaf in which feeding continues. They do not feed on mature leaves.
When the female reaches maturity 10 to 15 days after feeding initiation and gall formation is complete, eggs are deposited inside the gall. Up to 200 to 300 eggs may be deposited by a single female over a period of 30 to 40 days. As eggs hatch, the new nymphs immediately emerge from the gall through a small exit hole on the upper leaf surface. The nymphs move to additional locations and begin feeding and new galls are formed. The lifecycle is repeated as the shoot grows and the season progresses. In the fall, some hatching nymphs migrate, are windblown or fall to the ground and crawl down to the root system to hibernate through the winter.
Heavily galled leaves are malformed and rolled, causing a decrease in leaf surface area. Leaf gall tissue may contain up to 90% less chlorophyll than healthy leaf tissue, suggesting a reduction of photosynthesis. The loss of carbohydrates, due to severe infestations, could result in reduced fruit sugar levels at harvest. The vine may also be unable to adequately store carbohydrates as food reserves, which would otherwise promote winter hardiness and supply energy for new growth the following spring. Severe infestations of phylloxera galls on the foliage will also cause defoliation and restrict shoot growth.
Frontenac and Frontenac Gris, Marechal Foch, Baco Noir, St. Vincent, Seyval and Vidal often exhibit severe infestations. The worst infestations often occur on the vineyard edges, shady areas or on stressed vines located on poor soils. Wild grapes growing near field edges are routinely infested and provide a source of infestation.
Period of Activity
First galls develop at 3-5 leaves. New galls continue to be produced on young leaves with successive generations of crawlers.
Scouting Notes
Monitoring of the leaf feeding cycle of grape phylloxera depends on timely visual observations. Galls begin appearing in mid-May, usually as one or two galls on the first to third new expanding leaves. When galls are first noticed, they should be sliced open with a razor daily until the eggs have started to hatch. Only then, when the tiny crawlers are active and moving are they susceptible to an insecticide application. Later in the season the generations of active crawlers are non-synchronous, and insecticides have little effect on the overall infestation.
Threshold
On very susceptible cultivars, especially on young plantings, apply treatments at development of first galls in the spring. In blocks with histories of infestation, the first insecticide should be applied when crawlers first appear from the galls as monitored by above process. Repeat applications may be required if new galls are observed on newly expanding leaves 14 to 21 days after first treatment.
Management Notes
In major grape growing regions, phylloxera-tolerant American rootstocks are used to cultivate V. vinifera. In Ontario vineyards, the grape phylloxera inhabits most rootstock root systems but has no lethal effects due to low winter temperatures which prevent excessive build-up of phylloxera population.
Growers should be aware that the following cultivars hybridized from French V. vinifera and American Vitis species can sustain economically damaging leaf galling by grape phylloxera: Aurora, Cascade, Catawba, Cayuga White, Chambourcin, Chancellor, Chelois, DeChaunac, Delaware, Frontenac, Frontenac Gris, Himrod, La Crescent, LaCrosse, Lakemont, Norton/Cynthiana, Rayon D’Or, Reliance, Rougeon, St. Croix, Seibel, Seyval, Vidal, Vidal Blanc, Vignoles.
Management with insecticides - Insecticides may be used to control phylloxera in hybrid vineyards. See OMAFRA Publication 360, Fruit Crop Protection Guide - Chapter 4 Grapes: Recommendations for phylloxera at Shoot Length 20-25 cm, Trace bloom, Immediate postbloom to early fruit set and Berries pea-sized.
