Each crop is susceptible to certain insects, diseases, and weeds—onions in Malheur County are especially affected by thrips, iris yellow spot virus, and competition with weeds, especially yellow nutsedge.(C. C. Shock, personal communication, 2013.) Repeated planting of the same crop accentuates most of the afflictions of that particular crop because pests have the opportunity to persist and increase. Rotating crops is done by planting one crop in a field for a season, and then planting a different crop in that same field the next season. This helps control insect, disease, and weed infestations by limiting crops’ existence to one season in a designated field every few years. It can also improve soil quality. Onions in Malheur County are usually rotated on a 4-5 year basis with corn, wheat, potatoes, sugar beets, alfalfa, and other crops.
Crop rotation is an essential part of sustainable agriculture. If used with other sustainable pest control practices, crop rotation can contribute to the control of pest organisms.