If two heads are better than one, imagine 18 entomologists from the southern half of the nation gathering to share their insights on best management practices (BMPs) for pest control in vegetables.
That’s just what occurred during a vegetable entomologist workshop held in Monterey, Calif., last May.
“We gathered our collective minds to identify some of the best management practices for pest management and control in vegetables in various growing areas,” said John Palumbo, an entomologist who participated in the workshop. Palumbo is an Extension specialist based at the Yuma Agricultural Center (YAC), Yuma, Ariz.
Six other entomologists represented Western vegetable production at the workshop including: Mohammed Bari, USDA–ARS, Salinas, Calif.; Steve Castle, USDA–ARS, Maricopa, Ariz.; Toby Glik, University of California Cooperative Extension, Monterey County, Salinas, Calif.; Eric Natwick, UCCE, Imperial County, Holtville, Calif.; and Nilima Prabhaker and Nick Toscano, both from UC Riverside, Riverside, Calif.
Based on the collaborative feedback at the workshop, the group developed a draft of the BMPs they believe have the best fit for desert-cropping systems for winter vegetable production.
Palumbo shared the BMPs with growers, pest control advisors, and industry representatives during the 19th annual Fall Desert Crops Workshop in Holtville, Calif., in November. The workshop was sponsored by Western Farm Press.
While some BMPs are common knowledge, others stress the importance of a thorough understanding of individual crops, pests, and chemicals.
The group’s 11 recommended BMPs include the following:
1. Successful insect management for safe and efficient crop production should include good coordination and communication of management activities between growers and consultants.
“Excellent communication between the growing operation, pest management operation, and ancillary operations is essential,” Palumbo said. “This is becoming more and more critical with labor issues and maximum residue levels.”
2. “A solid first line of defense” is adopting cultural practices which avoid or prevent the buildup of insects; for instance crop rotation, sanitation, plus crop residue and destruction. Optimal crop management is also critical plus understanding the long-term impact of herbicides, insecticides, and fungicides in terms of plant-back restrictions.
Palumbo points to the outbreak two years ago of the cucurbit yellow stunting disorder virus (CYSDV) in cucurbits grown in California and Arizona’s low desert. While CYSDV still exists, growers have minimized the impact through good cultural practices, i.e. host-free periods, disk downs, sanitation, in addition to good chemical management to manage whiteflies and the virus.
3. Monitoring and sampling for pests by crop stage and pest species helps make informed management decisions. This must be achieved separately for each pest, pest stage, and crop stage, Palumbo says.
4. Know the pest spectrum, plus pest trends in the area and the cropping system during the growing season. The spectrum can be quite different from one growing area to another.
For example, the leafy vegetable cropping system in the Yuma area includes planting from about September to December with harvest from about mid-November to April. Temperatures influence crop growth and the pest spectrum.
Whiteflies, leafminers, and beetles become problematic with warmer temperatures in the fall while aphids and thrips are a threat in the cooler spring. An understanding of the interaction between the specific growing season, cropping system, and environment are critical to understanding how the pest spectrum impacts the crop.
5. Accurate identification of insect species is essential before making pest management decisions. In Yuma, vegetable growers find winged aphids during the early fall. It’s important to determine the correct species since many winged aphids found in lettuce this time of the year are not economically important.
“It’s important to know species-by-species what you’re dealing with so you don’t waste a spray or make a poor management decision, Palumbo said.
6. Scouting in accordance with a scientifically validated sampling plan when available helps to quantify pest numbers by species to determine the need for control based on economic injury theory. Several sampling plans exist (i.e. whiteflies on melons, leps in lettuce), but not for all pests.
“Thrips is difficult to work with and monitor, and we don’t have any scientifically validated sampling plans for them,” Palumbo said. “That can’t stop you from making successful management decisions, but it makes it more difficult to decide when to treat. The industry has learned from experience when to treat and when not to treat.”
7. Select the correct pesticide for the need when pest populations reach an action threshold and control is necessary. Choose the pesticide by value, efficacy, residual activity, and the spectrum of control. It is important to rotate modes of action.
Also consider eco-friendly pesticides. Use insecticides compatible with the activity of beneficial insects. When possible avoid broad spectrum insecticides. When used, do so selectively.
8. A thorough understanding of the pesticide’s biological activity, plus the biology and ecology of the target pest, is essential for application timing and post-treatment evaluation.
“A classic example would be a synergized pyrethroid for whiteflies where the adult stage is targeted,” Palumbo said. “By knocking out the adult, egg-laying is reduced which reduces the number of immature pests that can cycle though to the next generation.” In contrast, insect growth regulators such as Courier target the immature stages directly, and prevent nymphs from completing the life cycle.
9. The correct timing of pesticide applications according to thresholds is critical. Three IPM models apply. A pre-plant preventive model that’s a good fit for desert-grown vegetables includes the products Imidacloprid, Alias (MANA) or Admire (Bayer) to prevent whitefly colonization on seedling plants.
The preemptive model is based on experience and intuition. “The Imperial Valley corn industry knows the corn ear worm is always a problem in sweet corn,” Palumbo said. “The worm will always occur and when silking begins the treatment must follow. Once you have problems, it’s hard to catch up.”
The reactive model realizes a pest threshold exists and once the threshold is exceeded, the crop must be treated immediately to prevent economic losses.
10. Utilize weather patterns as a predictive model for insect pressure, population growth, insect stages, and for choosing the correct insecticide. Palumbo is a self-described addict of watching the Weather Channel for good reason.
“Those in farm fields consider themselves amateur meteorologists,” Palumbo said. “When trying to predict insect pressure, length of the pressure, population growth, and the length of development, it’s smart to consider temperature, humidity, and what’s the forecast for the next two to three weeks. When a low weather system is brewing off the coast, think about what will happen with pests in the near future.”
11. Crop, contract, or market trends will help quantify crop value in assessing the risks and benefits of insecticide applications. “Quality is essential,” Palumbo said. “You must have a quality crop – bottom line. Quality is more essential in vegetables than any other crop.”