Striped cucumber beetle adult.
Mating squash bugs.
It’s mid May on the calendar but given how warm it is, it might seem more like late May or early June to some early season cucurbit pests. Based on our biweekly fruit and vegetable conference calls, no cucumber beetles or squash bugs have been reported in the state.
As growers begin to plan for direct seeding or transplanting, keep an eye out for striped cucumber beetles and squash bugs in particular. Earliest planted fields will likely be infested soon after emergence or when placed in the field. For growers who purchased seed treated with FarMoreFI400, striped cucumber beetle populations should be controlled for 2-3 weeks. After this period if scouting reveals beetles in excess of plant stage threshold, foliar treatments are an option. For growers who did not purchase systemic insecticide treated seed, remember to scout plants frequently in multiple parts of the field, edge and interior, and if the damage exceeds the following thresholds, consider treating with a foliar insecticide to knock these pests down. Foliar insecticide options can be found here: https://mwveguide.org/uploads/pdfs/Cucurbit-Crops_2023-12-20-141555_pieo.pdf
Systemic insecticide use and guidance on cucumber beetle thresholds based on crop type is listed in detail below based on an excerpt from an earlier VegNet article from J. Jasinski and C. Welty (2020).
Characteristic striped cucumber beetle feeding. FarMoreFI400 should prevent significant feeding and therefore limit bacterial wilt spread.
Systemic Insecticide Use Considerations
Seed treatments containing thiamethoxam (FarMore FI400, Cruiser) offer maximum protection against cucumber beetles and other pests for about 2 to 3 weeks after seedling emergence. Seed treatments offer little protection to transplanted crops. For transplants and direct-seeded plants over 3 weeks old, the concentration of insecticide from seed treatment is no longer strong enough to kill beetles but can still harm bees due to sublethal doses in the pollen and nectar. Treated seed should never be used in combination with at-plant soil drenches with flupyradifurone (Sivanto), imidacloprid (Admire or generics), or thiamethoxam (Platinum). At-plant soil drenches used alone, with non-treated seed, offer similar protection to treated seed for beetle control. Due to increased residues in nectar and pollen, in-furrow applications should be considered last and applied at the lowest recommended rate that provides control. Non-systemic foliar applications of insecticides can be used to control cucumber beetles if seed or in-furrow treatments were not used, or were ineffective. Once flowers are present, applications should be made in the evening when flowers are closed and bees are not actively foraging, which minimizes the risk to pollinators.
Thresholds range from 0.5 to 1 beetle per seedling, and 1 to 5 beetles per plant for plants after 4 leaf stage. The threshold for cantaloupe melons and cucumber is lower because these crops are susceptible to bacterial wilt, which is vectored by cucumber beetles. Pumpkin, squash, and watermelon have higher thresholds because these crops are less susceptible to bacterial wilt, but beetle feeding can occur on the fruit rind by both adult and larvae, causing marketable loss. Beetles found in pumpkin or squash flowers do not pose a risk to the plant but as flowering decreases, rind feeding may increase.
Pumpkin playlist on OSU IPM Video Library.
OSU IPM Video Library
Newly added this spring are additional resources in the OSU IPM Video Library. These resources help growers identify and manage all of the key cucurbit pests including striped cucumber beetle, squash bug and squash vine borer plus a new potential pest, the melonworm.
Videos on weed control, disease control (powdery mildew, plectosporium) and hybrid selection are also in this playlist collection.
https://www.youtube.com/playlist?list=PL0HRPaZDLHyH64oVLKdX5icKQFzqQ5nCA
