Historically, our Areawide Pheromone and Sticky Trap monitoring for insects was terminated around the first of April as the produce season ended. Beginning 2 years ago however, we continued our Areawide Trapping Network throughout the summer to collect trapping data from all 16 areawide trap locations year-round.  So why is this additional trapping data useful? For several reasons. First, understanding the activity of some of our key pests when produce is not grown during the summer may give us an indication of what to expect as the fall produce season begins. This may be particularly helpful for predicting moth flights and whitefly flights in August-September coinciding with early transplanting and direct seeded crops.  Another example is keeping track of corn earworm which can unexpectedly show up near the beginning of fall harvests. Secondly, trapping for pests during the summer has shown us that 2 of our more important produce pests are not caught in traps during the summer. We presume this is due to the absence of brassica crops and weeds for diamondback moth, and high daytime/nighttime temperatures lethal to aphids. The fact that trap catches resume in the fall supports our conclusion that these pests are absent in the summer, only to reenter the desert via winds and/or transplants in the fall. And finally, it gives me something to do in the summer.  So, visit the Areawide Summer Trap Network if you’re curious what our key pests are up to. We also continue to monitor thrips activity during the summer. This involves plant sampling using a dislodgement sampling method (beat pan) to determine the relative abundance of thrips adults and larvae on alfalfa, cotton, melons, wheat, Sudan grass, and weeds.  This is being conducted to supplement our yellow sticky trap data that only indicates thrips adult flight movement an area. With this plant sampling we should be able to determine the primary host plants thrips are colonizing in the cropping season during the long hot summer. We are also trying to determine whether these crops allow for the reproduction of thrips. So far, all the crops and weeds we have sampled have shown that thrips will reproduce and complete their life cycle on them. This is important, particularly for weeds, as we are trying to determine whether INSV can be survive the summer in the absence of lettuce. It is also important because it allows us to determine potential exposure of thrips to key insecticides like Radiant and Lannate for resistance management purposes. These crops essentially serve as untreated refugia that likely sustains insecticide susceptibility and is the reason these products are still effective against thrips.  We will be conducting this work throughout the summer, as well as through next produce season. We will periodically provide updates of these thrips monitoring results throughout the summer.  As my dad used to say, “to solve the problem, you must first understand the problem”.

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Revere’ was seeded, then sprinkler-irrigated to germinate seed Jan 18, 2024 on beds with 84 in. between bed centers and containing 30 lines of seed per bed.  All irrigation water was supplied by sprinkler irrigation.  Treatments were replicated four times in a randomized complete block design.  Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed.  Treatments were applied with a CO₂backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles. 
 

Month	Max	Min	Average	Rainfall
January	68	42	54	1.14 in
February	73	47	59	0.50 in
March	77	50	63	0.31 in

 
Downy mildew (caused by Peronospora farinosa f. sp. spinaciae) was first observed in plots on Feb 19  and final reading was taken on February 26, 2024. Spray date for each treatments are listed in excel file with the results.   Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft² areas within each of the four replicate plots per treatment.  The number of spinach leaves in a 1-ft² area of bed was approximately 144. 

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that  provided effective control against the disease include Orondis ultra, Thrive 4 M, Fungout, Cevya, Eject and Zampro. No phytotoxicity was observed in any of the treatments in this trial.

The weeds here are constantly changing due mostly to changing production and management practices. These changes are normally slow although once a species becomes widespread, it may seem like it has come out of nowhere. Some have come out of nowhere when they are introduced with seed or equipment from another area but most are not new. Three weed species that have been brought to us in recent years that we have never seen here before are Seaside Petunia, Hairy fleabane and Southern brass buttons. 

Seaside Petunia (Calibrachoa parviflora) 
This was found in melons in the Yuma area this season. It is in the nightshade family and is native to the southwestern U.S. It has small petunia-like purple flowers and fleshy, sticky leaves. The stems are thin, creep along the ground and root at the nodes. It can form dense mats. The flowers resemble a miniature version of cultivated petunias.

Hairy Fleabane (Conyza bonariensis) 
This was found in onions in the Parker Valley this year. It is widespread in California but not in S.W. Arizona. It resembles and is in the same family as horseweed or marstail. Marstail has become more widespread in recent years. Marstail is Conyza canadensis and Hairy fleabane is Conyza bonarinsis. Glyphosate- resistant biotypes have been confirmed in California. It is classified as a summer annual but can be found here year round. When fleabane is small it looks very similar to marstail. It is prolific and produces large quantities of seed that are distributed by wind. Unlike many weeds, fleabane seed does not have a long longevity. It is viable for only 3 or 4 years.
Southern Brass Buttons (Cotula cornopifolia) 
Found in the Parker are 4 or 5 years ago, Brass buttons is often confused with swinecress. The leaves and flowerhead look very similar to swinecress. It is salt tolerant and often found in saline areas. It gets its name from its flowers which are bright yellow, round and thick. It is a perennial in the composite family that was introduced from Europe and Africa. It is relatively short, branches and can root at the nodes.

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 20, Oct 2, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:             
CEW moth counts low in most traps; below average for this early produce season. 
 
Beet armyworm:         
Trap counts decreasing in most areas, and below average for late September
 
Cabbage looper:          
Cabbage looper trap counts low in all locations, typical for mid-late September.
 
Diamondback moth:   
Adult activity beginning to pick up in Dome Valley.  Overall, typical of late September with minimal monsson activity.
 
Whitefly:                       
Adult movement most active in Dome Valley; overall below average for mid September
 
Thrips:                          
Thrips adult movement light; overall activity typical for September. 
 
Aphids:                        
Aphid movement absent so far; anticipate activity to pick up when winds beginning blowing from N-NW. 
 
Leafminers:                  
Adult activity light in all areas, about average for this time of season.