It’s quite disturbing when you’ve been waiting all winter for green growth from the tiny compact grape buds, only to have them cleaned out by cutworms!
The warm weather that moves the grape buds out of dormancy is also stimulating the emergence of a small larvae from the soil, known as the cutworm. If you’ve been spending time in the garden lately, then you will have come across one of these soft bodied larva. Forming a characteristic C when disturbed, they hide in the soil by day, emerging at night to wreak havoc.In BC there are 17 species of cutworm that can attack and eat emerging grape buds, but the most significant one is the moth Abagrotis orbis. Over the winter, these larvae hide under leaf debris in the soil, waiting for the right conditions (ah… warm) to emerge. In a few nights, the cutworm will climb the vines and feed on the developing buds. Because of their voracious appetite, a tremendous amount of chewing damage can happen overnight. Once the shoots start growing, they quickly grow to a size that cutworm feeding has minimal impact.
Although this pest can be easily controlled with pesticides, it`s hard to apply a preventative spray. Cutworm populations vary considerably from year to year and often they don`t cause enough damage to warrant a spray. At this time of the year it is critical that the vineyard is monitored frequently for signs of feeding damage.
In our vineyards, because of our crop expectaions, we usually do not apply a control spray unless we see 5 % or more chewed buds in a block.Research has shown that damage tends to be lower in vineyards with mixed cover crops, especially if they are populated with Draba verna and Shepherd’s purse, Capsella bursa-pastoris.
If you want to learn more, information can be found at the BC Ministry of Agriculture site: http://www.agf.gov.bc.ca/cropprot/grapeipm/cutworms.htm