In the next 2-3 weeks, pumpkin, squash, melon and cucumber growers looking for an early crop will start direct seeding in the field or preparing seed flats for later transplanting out in the field. One of the perennial pest’s growers run into is the striped cucumber beetle which can attack seedling plants and chew them nearly to the ground. In addition to the physical damage the beetles can inflict, there is also a chance that some can transmit bacterial wilt to the plant which will prevent it from setting mature fruit.
A variety of control measures and tactics to manage cucumber beetles and bacterial wilt are reviewed in this recent video (https://youtu.be/RSzTT_gbma4) which includes methods to limit the impact of these early season treatments on pollinators.
Here is a quick review of the recommended options:
- Plant fungicide only treated seed, scout fields frequently and treat with a foliar insecticide if the cucumber beetle threshold per plant is exceeded. Typically we think of 0.5 beetles per plant at the cotyledon stage or 1-2 beetles per plant at 1-4 leaf stage as general thresholds.
- Plant systemic insecticide treated seed (FarMore FI400) to control cucumber beetles for 2-3 weeks in the field after seedling emergence.
- Sow trays with fungicide only treated seeds in a greenhouse or high tunnel, then treat transplants with systemic insecticides on benchtop just prior to transplanting or drench transplants in the field using treated water. If using this technique do NOT use FarMore FI400 treated seed as it will not control cucumber beetles when transplanted but additional insecticide residue will be present in the pollen and nectar.
- Use systemic insecticide products in-furrow at planting time; this technique will produce the highest amounts of insecticide in the pollen and nectar of any of the options outlined above so use the lowest effective rate.
For more information on all the recommended foliar and systemic insecticides for cucurbit insect pests, consult the Midwest Vegetable Control Guide (https://mwveguide.org/guide).