Grape bud swell: watch out for flea beetle and cutworm damage

Spring is finally here and grape buds are starting to swell. Now is the time to start scouting for insects that may hollow out grape buds. The main culprits of such type of damage are flea beetle and cutworms. Damage symptoms look similar, as both burrow into and hollow out developing buds around bud swell until bud break. However, it is important to determine which is causing damage, as control measures differ depending on which pest is present in your vineyard. For more detailed information about these insects, please refer to this previous article or to the Bud Swell Webinar recording. At this time, it is important to know that cooler temperatures in the spring tend to prolong the bud swell stage which provides a longer period of feeding activities for flea beetle and cutworms. The main differences between these groups of insects are described in the table below.
Cutworm https://psuwineandgrapes.wordpress.com Flea beetle
R. Bessin, University of Kentucky
Cutworms | Flea Beetle | |
Timing of activity | Larval damage at night | Adult damage during day |
Scouting | Scout at night on plants or during the day digging top soil around the plants | Scout during the day on plants |
Developmental stage affected | Bud swell through bud burst | Bud swell through bud burst |
Where they may be most prevalent | Sandy soils, weedy areas | Near forested edges |
Threshold | 2% bud damage | 2-4% bud damage |
Some chemical controls | Altacor, Belt, Brigade, Delegate, Lorsban, Baythroid, Danitol, Sevin | Baythroid, Danitol, Sevin, Imidan, Renounce, Scorpion |
For more chemical control recommendations, please refer to the Midwest Spray Guide. Please note some overlap in insecticide options between insect groups. The label is the law, please follow the label!
This article was posted in Grapes, Insects and tagged cold climate grapes, cutworm, flea beetle, WFN.