Grape Phylloxera, Daktulosphaira vitifoliae (Fitch)

Description and Life Cycle Phylloxera is one of the most destructive grape pests worldwide.  This small aphid-like insect has a complex life cycle that involves survival on the roots throughout the year, and on the leaves during the growing season.  The sequence of events in the life cycle is different for the foliar and root forms of this insect.  The foliar form survives the winter as an egg under the bark of the grapevine.  Asexual, wingless forms hatch in the spring and crawl onto the new leaves, where they develop galls.  Young crawlers settle on the upper surface of immature leaves, causing galls to form on the under surface of the leaves.  The only opening in a gall is to the upper leaf surface.  Once mature, the female begins to lay eggs within a gall.  Nymphs hatching from these eggs crawl to new leaves at shoot tips, settle on the leaves, and form new galls.

In the case of the root form of grape phylloxera, the insects overwinter as immature forms on the roots.  These forms mature in the spring and produce eggs that hatch into nymphs.  The nymphs then start new galls on the roots.  Winged forms develop in the spring, summer or fall and emerge from the soil to lay eggs on stems.  These eggs hatch and produce the true sexual forms that produce the overwintering eggs laid under the bark.  Several generations of each form of phylloxera may occur each season.  Although the two forms behave differently, both belong to the same species of phylloxera that occurs on the leaves and roots of grapes.

 

Damage Symptoms

The insect forms galls on the leaves and roots of grapevines.  The vine will die if its roots become heavily infested with phylloxera.  If leaves become heavily infested, premature defoliation and retarded shoot growth may result.

Management

In many areas of the world, susceptible cultivars are grafted onto resistant rootstocks to prevent damage by the root form.  However, the foliar form still may occur in such cases.  Currently only one insecticide is labeled for the foliar form of grape phylloxera.  There are some natural predators which feed upon the foliar form of grape phylloxera, but none of these provide adequate control of the pest.  There is no known completely successful chemical control for the root form of gape phylloxera.  Eastern growers usually do not have a problem with the root form of the phylloxera.   

Monitoring

Phylloxera is usually spotty in Ohio vineyards, so identifying these areas within your vineyard is important.  Spot treatment may be all that is required to control this pest.  To identify the location and extent of phylloxera within a vineyard, one should begin scouting for infested leaves after shoot length has reached five inches.  Young galls will be forming on the underside of the terminal leaves, they are not easily noticed early in the season with out taking the time to inspect the leaves closely.  These galls should not be confused with grape tumid galls, commonly called the grape tomato gall.  Tumid galls have a smooth outer surface and take on a reddish tomato like appearance whereas the grape phylloxera gall is green in appearance except early in the season when young grape leaves tend to have more of a reddish cast to them.  The gall itself has a rough looking surface rather than the smooth surface of the tumid gall.  Tumid gall is present but not a problem in Ohio vineyards.

Control

Native American grapes tend to have resistance to grape phylloxera and are not a problem, however French hybrid and vinifera grapes are usually very susceptible and control of phylloxera on these cultivars is recommended.  One can not usually completely eradicate phylloxera from a vineyard that is already infested but can take measures to keep the infestation at a tolerable level.  Control of the foliar form of phylloxera may be achieved by applying insecticide at bloom and again 10 to 14 days later.  Late season treatment of grape phylloxera is not effective and is a waste of time and money.  Early season control of this pest is critical. 

Root Form of Grape Phylloxera, Daktulosphaira vitifoliae (Fitch)

In the case of the root form of grape phylloxera, the insects overwinter as immature forms on the roots.  These forms mature in the spring and produce eggs that hatch into nymphs.  The nymphs then start new galls on the roots.  Winged forms develop in the spring, summer or fall and emerge from the soil to lay eggs on stems.  These eggs hatch and produce the true sexual forms that produce the overwintering eggs laid under the bark.  Several generations of each form of phylloxera may occur each season.  Although the two forms behave differently, both belong to the same species of phylloxera that occurs on the leaves and roots of grapes.

Management

In many areas of the world, susceptible cultivars are grafted onto resistant rootstocks to prevent damage by the root form.  However, the foliar form still may occur in such cases.  Currently only one insecticide is labeled for the foliar form of grape phylloxera.  There are some natural predators which feed upon the foliar form of grape phylloxera, but none of these provide adequate control of the pest.  There is no known completely successful chemical control for the root form of gape phylloxera.  Eastern growers usually do not have a problem with the root form of the phylloxera but it does serve as a resource for the foliar form.

Current pesticide recommendations may be found HERE

 

Home