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Alternative Perimeter Trap Crops for Squash

Cucumber beetles are serious insect pests of cucurbit crops, causing direct damage by feeding and indirectly through transmission of diseases including bacterial wilt. Management typically involves cultural practices such as altered planting dates, monitoring for pest activity and the use of pesticides targeting adults. Perimeter (border) trap crops have also been used to help control pest populations and reduce pesticide use.

Perimeter trap cropping (PTC) is a technique used in IPM to reduce pesticide use through adjustments in crop layout. An alternative host plant attractive to colonizing pest insects is planted to completely encircle the main crop. The trap crop may be from the same or different plant family as the main crop, as long as it is more attractive to the pest for feeding or egg-laying than the main crop. The effectiveness of this IPM technique can be improved by spraying a pesticide on the PTC (but not the main crop) when the insect pest arrives, preventing or reducing movement into the main crop. Another advantage of spraying only the trap crop is that many of the natural enemies are preserved.

The potential for PTC in reducing damage to the main crops has been demonstrated in other crops such as peppers, cabbage and potatoes. Research indicates that Blue Hubbard squash is an effective border for butternut and summer squash for management of cucumber beetles and squash vine borers. However, the crop may have limited market demand.

Successful pollination is important for many cucurbit crops to maximize yield. Pollinating insects including honey bees and native specialists have preferences to different flowing plants. On the down side, if PTC varieties are more attractive than the main crop, yield could be reduced due to competition for pollinators. On the plus side, if PTC varieties attract more pollinators to the area overall, yield may increase.

In a recently published study by Adler and Hazzard (2009), researchers at the University of Massachusetts, different PTC were examined in terms of their impact on insect damage to and pollination of butternut squash (Environmental Entomology 38:207-215). Crops chosen for the PTC included Blue Hubbard, buttercup squash (cultivar Burgess), zucchini (cultivar Embassy), and wild gourd mixed with zucchini. The results indicate that both buttercup squash and zucchini are as attractive to cucumber beetles as Blue Hubbard (wild gourd was unattractive). There was no evidence that any of the border crops evaluated in this trial competed with the main crop for pollinators. The authors conclude that buttercup squash and zucchini as viable alternatives to Blue Hubbard as PTC for butternut squash.

Tips on making PTC work include: (1) practice crop rotation and plant crop at least 1 km away from where you did last year; (2) completely encircle the crop; (3) large square or rectangular blocks work best; (4) plant the trap crop a little earlier than the main crop; (5) manage cucumber beetles in the trap crop - don't allow them to overrun and kill it; (6) keep the trap crop healthy. In areas with higher pressure, the PTC should be multiple rows wide. If more than 0.1-5.0 beetles/trap crop plant are found during scouting activities, supplemental insecticides in the main crop may be required.