A post-pruning spray of lime sulfur solution on all parts of the vine is generally recognized as a good idea. This material is available in several preparations and may be called "dormant oil."
Apply the material liberally with a hand gun, or air blast with nozzles aimed low.
Apply before bud swell!
The material will be injurious to breaking buds.
Apple growers consider a dormant spray as essential for elimination of over-wintering rust and scale which, if left unchecked, can take a crop, or at least render it unmarketable.
Grape growers take a more relaxed approach to dormant spray (few growers I know bother with it at all). Let's face it: The apple grower has a definite advantage in terms of the smooth surface he is applying the material to. Spraying the loose bark of a vine trunk with its seemingly unlimited pockets and crevices in which something may be hiding, does not give one an overwhelming sense of achievement.
Be assured, however, that there are enemies hiding on the vine in the form of mildew spores and some insect larvae (see grape scale, brown scale and flea beetle). They are looking for an opportunity to get a foothold and they may have four or five weeks of mild weather to work in before you commence your regular spray schedule.
Flea beetles deserve special attention. Their calling card is left in your vineyard in the form of hollowed buds that never had a chance. Since we prune to limit bud numbers, losing a few can substantially reduce productivity.
The timing of a dormant spray application is not perfect for flea beetles. As noted above, the application should occur before bud swell. Most adult flea beetles are just starting to move from the vineyard floor to the vines at this point. Do we kill them with the dormant spray? Does the dormant spray material create a less hospitable environment for egg sacks and larvae? Even the experts agree on this one: It is worth a shot (of lime sulfur solution).
If you see the flea beetle's calling card, take it seriously. If you don't fight them, the population will increase each year. After the dormant spray and before regular spraying begins, use a hand gun to apply whatever insecticide you have available that is labeled for flea beetles. Apply to swelling and breaking buds.
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