Managing Vineyard Insect and Mite Pests
Grape Leaffolder
Grape leaffolder (Desmia funeralis) larvae feed on leaves causing the margins of leaves to either fold or roll downward (See Figure 22.7).
Symptoms
In its larval stage, grape leaffolder rolls and feeds on leaves, reducing photosynthetic function. They then feed on the edge of the leaf within the roll.
Life Cycle
After overwintering as pupae in the folded and fallen leaves, moths emerge in the spring and lay eggs on the leaves. Usually the eggs are deposited against the leaf veins on the underside of the leaf.
Monitoring
No commercial sex pheromone is available for monitoring adult flights. Growers can use malt syrup or terpinyl acetate bait traps to follow the moth flights, but since there is no validated phenology model available to interpret the flights, trapping is of little use.
Cultural Pest Control
During the dormant season remove mummy clusters and control vineyard weeds. Early harvest can also prevent infestation by fourth generation larvae.
Biological Pest Control
Several parasites attack grape leaffolder. Among the most common is the larval parasite Braconid wasp (Bracon cushmani).
Biorational Pest Control
Microbials
Organic growers have the option in controlling grape leaffolder using microbial insecticides such as Bacillus thuringiensis and spinosad. Bacillus thuringiensis bloom sprays are only effective against young larvae. Good spray coverage is essential.
Chemical Pest Control
Standard insecticides include Kryocide (cryolite), Intrepid (methoxyfenozide), Altacor (chlorantraniliprole), Belt (flubendiamide), and Delegate (spinetoram). Insecticides used for controlling grape leaffolder in vineyards are presented in Appendix K, Insecticides Registered for Use in Vineyards.
Applying Control Materials
Treat for grape leaffolder at bloom if the vineyard has a history of this pest or if a serious infestation occurred in the previous season. First-generation larvae are usually controlled by bloom sprays. Bloom is also preferred time for application because of limited foliage and open clusters allow for better coverage. Grape leaffolder populations can increase several-fold within the season; so later generations may also need to be controlled. Later in the season populations are more difficult to control because of greater leaf canopy, especially if leaf rolling has taken place.
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