Have you tried Perimeter Trap Cropping yet?
Cucumber beetles can cause direct damage to seedlings between the cotyledon and third true leaf stage. That is also the stage when the plants are most susceptible to infection by the bacterial wilt pathogen, which is spread by the beetles. Perimeter trap cropping (PTC) has provided better protection from beetle and wilt damage than multiple, full-field insecticide applications on many Connecticut and Massachusetts farms. Perimeter trap cropping also spares natural enemies on the unsprayed main crop.
Directions: The trap crop (i.e. Blue Hubbard or other Cucurbita maxima squash) should be planted all the way around the main cucurbit crop you are trying to protect. Insecticide applications should be timed to protect the seedling trap crop plants as soon as beetles arrive from overwintering sites. Think of the trap crop as a “poisoned fence!” One to three weekly insecticide applications on the trap crop may be necessary. If not controlled, cucumber beetles disperse throughout the field over time. Using an effective insecticide (e.g. Sevin, Asana or Admire) to kill the colonizing beetle population while they are still on the trap crop is essential when using PTC for cucumber beetles, or higher levels of bacterial wilt could occur. Organic growers may need to reapply pyrethrin or other insecticides every three or four days during the seedling stage and/or supplement with clay applications (Surround) to the main crop. That is because botanicals tend to have a very short residual period of effectiveness and are less efficacious than conventional products.
Trap crop fruit can be marketed as food or ornamentals, or the plants can be pulled out at bloom to prevent competition between the main and trap crops. Competition is not a factor when PTC is used to protect large fields or short-season crops (cucumbers or summer squash), and it is minimal when used on full-season crops (butternut or acorn squash or melons). Much to their surprise, most growers have found that they can easily sell the Blue Hubbard squash. The sale of the Blue Hubbard alone has added an extra $500-$1,000/acre of cucurbits crops for some PTC growers. Almost every grower who has tried PTC has found it simpler to use and more profitable than full field sprays, and they get better control! Why not try PTC on your farm in 2005?
- Perimeter trap cropping works for garden-sized plantings or larger fields (1/8 to 40 acres).
- Perimeter trap cropping and crop rotation should be used together to prevent some cucumber beetles from overwintering within the field, and to help prevent an increase in the pest population over time.
- Plant the trap crop (i.e. Blue Hubbard) so that it completely encircles the main crop without any large gaps in the perimeter. In bare-ground plantings, all of the trap crop seeding can be done by machine (both across the tops of the rows and along the outer rows).
- Plant the trap crop on good ground, so that it remains healthy throughout the pre-bloom period. In plasticulture systems, planting the trap crop on the outer edge (3 to 6″) of the plastic/bed works best to provide large, healthy, trap crop plants. Do not plant the trap crop in the drainage ditch or on compacted roadways. You’ll also need 2-4 trap crop plants at both ends of each bed.
- Plant the trap crop at the same time as (or before) the main crop. Seeds or transplants work equally well, as long as the trap crop plants are at least as big as the main crop plants between emergence and bloom.
- Plant the trap crop at the same in-row and between-row spacing as the main crop, with 1 to 3 trap crop rows along the length of the planting and 2 to 6 seeds or plants at the ends of each row. Multiple trap crop rows may be needed if extreme pest pressure is expected, or along tree lines where the heaviest pest pressure usually occurs as beetles colonize the fields from overwintering sites in the woods.
- Spray the perimeter plants as soon as the first beetle appears and begins to feed on the trap crop. Do not wait for the beetles to colonize the main crop or for a threshold level to be exceeded on the trap crop. Carbaryl (Sevin) and synthetic pyrethroids (e.g. Asana) work well, as does a preventative soil drench of imidacloprid (Admire) at planting.
- In large plantings, perimeter sprays easily can be applied by circling the field once with a boom sprayer or mist blower. In smaller plantings, the trap crop usually can be sprayed with a backpack sprayer faster than the whole planting can be sprayed with a large sprayer.
- Monitor the field weekly until bloom or harvest and be prepared to make 1 or 2 additional perimeter sprays or, if necessary, full-field applications. Repeat perimeter applications are necessary if rain washes the insecticide from the plants prematurely or if more live beetles are found on the trap crop prior to bloom. Full-field sprays should be applied when pest pressure is excessive on a particular farm, causing a breach in the perimeter and substantial main crop infestation (>½ beetle/plant for cucumbers or melons, >2 beetles/plant for squash).
- If the trap crop planting is incomplete or has large gaps (>15 ft) for any reason, treat the field as if it were a conventional planting (i.e. spray the whole field as often as needed). For example, you do not have an effective perimeter if you fail to plant along one side of the field or if wet conditions prevent the emergence of most of the trap crop plants. Gaps (<15 ft) from harvest or spray alleys will not adversely affect the ability of the trap crop to stop the beetle.
After you try PTC, let us know what you think. We’d love to hear from you.
Research sponsored by NE SARE
By: Jude Boucher & Rob Durgy, University of Connecticut; Ruth Hazzard & Andy Cavanagh, University of Massachusetts. 2005. Reviewed 2012.
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