This report details the impact and management of diamondback moth (DBM), Plutella xylostella, on desert Cole crops during the 2017–2018 season, following a major insecticide-resistant outbreak in 2016. Survey results from growers and pest control advisors (PCAs) across Arizona and California indicate that DBM pressure in 2017 was significantly reduced, with few reports of resistance or crop losses. Field and lab data confirmed that DBM populations in 2017 were susceptible to commonly used insecticides, including diamides. The findings support the hypothesis that 2017 infestations originated from distinct populations introduced via transplants or weather events, rather than persistent local resistance.

This publication examines how local weather patterns—particularly temperature, moisture, and wind—influence insect pest development, behavior, and abundance in desert vegetable cropping systems. It highlights how extreme conditions such as heat, cold, rainfall, and wind can either promote or suppress pest populations. Specific examples include the impact of temperature on whiteflies, aphids, and diamondback moths, the role of rain and humidity in insect mortality, and wind-driven pest dispersal into Arizona crop fields. These insights help explain seasonal trends and aid in forecasting pest outbreaks.

This IPM short provides updated information on the biology, damage potential, and management strategies for seed corn maggot (Delia platura) in spring melon production systems of the desert Southwest. The pest can cause serious injury to germinating seeds and transplants under cool, moist conditions, often exacerbated by high levels of organic matter. The publication outlines risk factors, preventive cultural practices, and effective insecticidal treatments to mitigate early-season losses in melon crops.

Lettuce produced in Arizona is susceptible to contamination by a variety of insect pests that can affect both market quality and food safety. This guide identifies common insect contaminants—including western flower thrips, aphids, leafhoppers, beet armyworms, and false chinch bugs—and describes their sources, behavior, and potential impact on harvested lettuce. Many of these pests migrate from surrounding crops or weedy areas and are often hidden between leaves or under the cap leaf, making detection challenging. Understanding their habits is critical for effective monitoring and contamination prevention strategies.

Western flower thrips (WFT), Frankliniella occidentalis, have emerged as serious pests of leafy vegetables in desert production systems, particularly lettuce and spinach. Their feeding causes cosmetic damage that reduces marketability, while their presence in harvested products poses contamination concerns. WFT are difficult to control due to their rapid development, cryptic feeding habits, and ability to disperse from surrounding vegetation. Management relies on regular field monitoring, timely insecticide applications at established action thresholds, and limited cultural strategies such as avoiding nearby infested fields and using overhead irrigation. Although natural enemies are present, they offer minimal suppression in desert conditions.

Foxglove aphid (Aulacorthum solani) has become a significant pest in desert lettuce and celery production since its detection in Arizona in 2002. Favoring cool-season crops, FGA causes contamination in harvested produce, especially in lettuce heads and celery hearts. This bulletin summarizes FGA identification, seasonal development, and management practices. Because systemic options are limited, foliar insecticide applications based on action thresholds are critical. Effective management relies on early detection and a preventative spray strategy to minimize marketable losses.

Aphids are the most economically important insect pests of lettuce, primarily due to their ability to rapidly infest crops and contaminate marketable heads. This bulletin outlines practical management strategies based on current research and field experience in desert lettuce production. Emphasis is placed on preventative cultural practices, conservation of natural enemies, frequent field scouting, and accurate species identification to guide control efforts. Because insecticide efficacy varies by aphid species, correct identification is essential for selecting effective treatments. A nominal action threshold treating when more than 5% of plants are infested is recommended to improve timing of foliar sprays and minimize unnecessary applications.

Corn earworm (Helicoverpa zea) is a significant pest in desert vegetable production, particularly head lettuce. This guide outlines its biology, host range, and seasonal activity, highlighting the economic damage caused by larvae boring into lettuce heads. Management recommendations emphasize field monitoring, species-specific action thresholds, and the timely application of selective insecticides. Effective control relies on early detection, accurate species identification, and integrating cultural, biological, and chemical strategies to prevent yield loss and contamination.

This publication provides an overview of action threshold (AT) guidelines for managing insect pests in leafy vegetables and cole crops in the desert Southwest. Developed from over 30 years of applied field research at the Yuma Agricultural Center, these thresholds help pest control advisors (PCAs) determine when insecticide applications are justified based on pest density or damage levels. The guide distinguishes between prevention strategies, nominal action thresholds, and zero-tolerance thresholds for market contamination, with specific thresholds for pests such as beet armyworm, whiteflies, aphids, thrips, and flea beetles. Emphasis is placed on integrating cultural, physical, and biological control methods before resorting to chemical control, reinforcing the core principles of Integrated Pest Management (IPM).