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.

Nutsedge is one of the most difficult to control weeds in Arizona and worldwide. It is a perennial that spreads vegetatively with below ground tubers that can stay viable for many years. Both yellow and purple nutsedge are common throughout Arizona. Most of it is purple which is the more difficult to control of the two. There are few herbicides that will completely control nutsedge and it is so prolific that even fairly high levels of control last only one season. Most herbicides need to be used for several consecutive years to keep this weed in check. 

When nutsedge infestations get worse every year it can become beneficial to combine summer fallow with chemical treatment to break the cycle and get the problem under control. One of the most effective and economical treatments for nutsedge control is Eptam (EPTC) combined with summer fallow. This technique can be highly effective but it can also completely fail if proper application and cultural practices are not followed. It was developed 25 years ago but is still often misunderstood. The following six principals are important for this technique to be effective: 

1) Both above ground shoots and below ground tubers must be destroyed. Emerged shoots will provide nutrients for the production of new below ground tubers. Viable below ground tubers will produce new rhizomes, basal bulbs and above ground shoots. Tillage and some herbicides such as glyphosate can be used to destroy above ground shoots. The Eptam fallow treatment will destroy rhizomes as they attempt to reach the surface. 

2) Eptam is one of the most volatile herbicides available. It is lost in several ways including microbiological and photochemical decomposition but the most common means of losing EPTC in the irrigated southwest is by contact with water. It volatizes from irrigation water, off of wet soil and is leached deep into the soil. It should be incorporated into dry soil where it will remain active for a much longer period of time. It should not be irrigated after application unless the objective is to move it down to contact deep tubers or to remove it in preparation for the planting of a susceptible crop. 

Red sprangletop is, in general, a lighter green color and has a finer seed head than does Mexican sprangletop which is darker green or gray and has a visibly coarser seedhead. Both form clumps or crowns that often survive through the winter months. Both are fairly tolerant to Poast (sethoxydim) and Fusilade (fluaziflop) but are controlled with high rates of Select (clethodim). 

3) Eptam works on those parts of the nutsedge plant that are trying to grow (rhizomes and shoots). It works best on stressed plants but will have no effect on nutlets that are dormant. Enough moisture should be made available to stimulate nutsedge growth but under stressed conditions. An irrigation may be necessary. Once the top 6 inches is dry the Eptam should be applied and incorporated. 

4) A chemical tarp is created with the surface application of Eptam that will prevent shoots and rhizomes from reaching the surface. The surface should, therefore, be left as smooth as possible. Any untreated areas or breaks in the surface from implements, wheels or even footprints will allow shoots to emerge. 

5) Eptam should not be applied too early (April or May) because of possible degradation prior to the period of rapid nutsedge growth or too late (August or September) because of decreasing growth and potential injury to fall planted crops. 

6) To avoid injury to following crops, irrigate at least 30 days prior to planting. The Eptam label specifies "Do not plant cotton or crops not listed on the Eptam label for 90 days after application." 

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 17, Aug 21, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts decreased areawide; about average to previous years.
 
Beet armyworm:         
BAW moth counts are up in south Yuma valley and Dome valley; about average for August

Cabbage looper:           
Cabbage looper numbers are low consistent with previous years and higher temperatures.
 
Diamondback moth:      
DBM moths were not caught in any trap; average for this time of the year.
 
Whitefly:                      
Adult movement continues to decrease, average for this time of the year.
 
Thrips:                          
Thrips adult activity continues to decline, average for August.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity declining and average for August.