Grape
Grapevine Phylloxera
Daktulosphaira vitifoliae
Insect
In a Nutshell
- Fleshy green or red galls on the lower side of the leaves and the tendrils.
- Abnormal leaf fall.
- Galls on roots.
- Reduced root system.
Can also be found in
Grape
Symptoms
Daktulosphaira vitifoliae has two galling-producing stages; a leaf galling stage and a root galling stage. Small galls develop on the lower surface of the leaf. The size of the galls is about the size of half a pea. Sometimes, the entire leaf can be covered by galls. Leaf galling does not normally cause significant losses in grape production. However, severe infestations do cause considerable distortion and dropping of affected leaves late in the season. Leaf-galling forms of phylloxera are rarely present in some countries. Note that leaf inhabiting forms do not occur without the root form also present. On the other hand, the infestation of the roots can be difficult to control and can lead to root swelling and the decline of vines. Degradation of the root system can cause secondary fungal infections. Severe root infestations can cause defoliation and reduce shoot growth. Death of susceptible vines may result within 3 - 10 years. Usually, symptoms are less significant on vigorous vines over 10 years old.
Recommendations
Organic Control
Little information on the biological control of grape phylloxera is available; environmental and root conditions are more important than natural enemies.
Chemical Control
Treating phylloxera with chemical tools is not always possible. On very sensitive cultivars, especially on young plants, it is necessary to treat as soon as the first galls develop in the spring. As soon as the galls appear, they must be opened daily by cutting them with a razor blade to detect when the eggs begin to hatch. Apply chemical control as soon as the small larvae are noticeable. Surveillance and early treatment application should be ensured so as not to reach the point of multiple generations with different life cycles co-existing. Insecticides have very little effect on these cases. Always use products regulated in your area.
What caused it?
The life cycle of Daktulosphaira vitifoliae is complex. This pest prefers heavy clay soils and dry conditions. In spring, the female hatches from a fertilized egg that had been laid on the wood of a grapevine, and migrate to a leaf where she produces a gall. Within 15 days, the female reaches maturity, fills the gall with eggs and dies soon afterwards. Nymphs that hatch from these eggs escape from the gall, and wander to new leaves. They produce new galls and eggs. During summer, there may be 6 or 7 generations. In the fall, nymphs migrate to the roots where they hibernate through the winter. The following spring they become active again and produce the root galls. Wingless females may cycle indefinitely on the roots year after year. In late summer and fall, some of the roots inhabiting phylloxera lay eggs that develop into winged females. Winged females migrate from the roots to the stems where they lay eggs of two sizes, the smaller ones developing into males and the larger ones into females. Mating occurs and the female then lays a single fertilized egg that overwinters on the grape stem. It is this egg that gives rise to leaf inhabiting generations. Depending on geographical factors, generations with different life cycles may develop at the same time.
Preventive Measures
- Resistant rootstocks (American rootstocks) have been the main and most successful control measure for many decades.
- All Vitis vinifera varieties and French hybrid cultivars are susceptible to injury from the root gall insect and it is.
- In general, rootstocks with no vinifera parentage have retained their resistance remarkably.
- In the past, flooding vineyards for several weeks was classically used.
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