The NOAA's Climate Prediction Center predicts that a moderate to strong La Niña will be the dominant climate factor influencing weather in Arizona and California this winter. This suggests that our local weather should be warmer and drier than average from December through February. So what impact will this have on insect pests normally found on leafy vegetables and melons this winter? Not real certain since predicting insect abundance is like predicting the weather. However, like the NOAA, we have collected data over the years that suggests that aphid pressure on lettuce is historically lighter during growing seasons when rainfall amounts are low (<0.25 inches). Similarly, seed corn maggot infestations are generally less severe under warm and dry growing conditions during the winter. In contrast, western flower thrips abundance has historically been higher under warm and dry weather conditions. Last winter (Jan-Mar) we received over 4 inches of rain in the Yuma Valley and thrips numbers were very low in our research trials, and seed corn maggots were quite damaging in a number of crops last spring. Thus, if one chooses to rely on the La Nina predictions, one might predict that aphid and seed corn maggot pressure will be lighter, and thrips numbers much heavier this winter and spring. But keep in mind there are a number of other abiotic and biotic factors that also influence insect abundance. Historical trends in insect abundance on desert crops and guidelines for their management were presented at the 21st Annual Desert Crops Workshop in El Centro last week. A copy of that presentation can be found at this link.

This study was conducted at the JV farms at Gila Valley. Lettuce variety ‘Guapo’ was seeded, then sprinkler-irrigated to germinate seed on September 19, 2023, on double rows 12 in. apart on beds with 42 in. between bed centers.  Rest of the irrigation was supplied by furrow irrigation or rainfall. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of 25 ft of bed, which contained two 25 ft rows of lettuce. Plants were thinned on October 9, 2023 at the 3-4 leaf stage to a 12-inch spacing. Treatment beds were separated by single nontreated beds. Treatments were applied by incorporating in soil before seeding or with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart.

Month	Max	Min	Avg	Rain
September	100	71	86	0.71 in
October	93	61	77	0.00 in
November	80	51	65	0.08 in
December	71	44	57	0.82 in

 
Fusarium wilt (caused by Fusarium oxysporum f. sp. lactucae ) rating was done in the field by observing the typical symptom of lettuce wilt. Confirmation was done by cutting the cross section of roots. Disease scoring/rating was done on December 6, 2023. 
 
The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. The disease pressure was extremely high in 2023, and most treatments showed little or no control against the disease. The treatments that showed some activity were Bexfond, Cevya, Rhyme, and Serifel. Plant vigor was normal and phytotoxicity symptoms were not observed in any treatments in this trial.

Plans are firming up for the 3^rd AgTech Field Demo: Automated & Robotic Technologies. The event will be held Tuesday, October 25th at the Yuma Agricultural Center. Registration begins at 7:00 am and the program starts at 7:30 am. The event will feature 15 of the latest automated and robotic technologies being demonstrated in the field (agenda below).
As mentioned in previous articles, we would love to showcase as many innovations as possible. It is getting a little late, but if you are interested in being added to the program, please let me know and we will do our best to try and accommodate you. It’s an open invitation - private companies, university and government researchers are all welcome to show their technology.

Fig. 1. Equipment being readied for demonstration at the 3^rd AgTech Field
Demo: Automated & Robotic Technologies being held October 25^th at the
University of Arizona’s Yuma Ag Center.

Faculty and staff at the Yuma Agriculture Center and Yuma Co. Extension office have been instructed to work from home when possible during this crisis. Fortunately, technology exists to continue most activities with little interruption. Some of our activities have been interrupted. One of these is conducting activities that offer Continuing Education Units. We are, however, exploring the opportunity to conduct meetings and workshops remotely that will qualify for CEU’s. Some opportunities already exist in which you can earn credits. Here are some sites that you can access to do this:

Western Farm Press
https://www.farmprogress.com/line-ce-course-available-free-western-farm-press-website?ag_brand=westernfarmpress.com

Certified Training Institute
https://www.certifiedtraininginstitute.com/pesticide/arizona-pesticide-continuing-education-courses/pmd-courses/

University of California Cooperative Extension
https://campus.extension.org/

UC Statewide IPM Program
http://ipm.ucanr.edu/training/
https://agceuonline.com

Check out courses, sort by accrediting state and topic.

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts decreased considerably y in the past 2 weeks and about average for late summer
 
Beet armyworm:         
Trap counts stay active in some locations (Yuma Dome Valley and Wellton) particularly near alfalfa
 
Cabbage looper:         
Cabbage looper numbers remain low consistent previous years.
 
Diamondback moth:      
DBM moths were not caught in any trap since June; average for this time of the year.
 
Whitefly:                      
Adult movement decreased in past 2 weeks consistent with previous years
 
Thrips:                         
Thrips adults decreasing in most locations, and trending comparable to previous years.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity has highest in Wellton and Dome Valley, and slightly above average for early August