As growers begin to prepare local fields for fall melons, they should be considering the threat of cucurbit yellow stunting disorder virus (CYSDV). The virus was first identified in desert melons in the fall of 2006 where widespread infection on cantaloupes, honeydews and other melons cost growers a significant portion of their crops. Without question, yields and quality in desert melon crops have been seriously affected by CYSDV infection. Additionally, melon pest management has been affected by CYSDV as insecticide usage on fall melons has increased significantly since 2006. Over the past eight years we have been studying the epidemiology of CYSDV and trying to develop approaches for reducing its impact on fall melon production. In addition, we continue to develop new information on control of the vector of CYSDV (Bemisia whitefly adults). Whitefly numbers this spring and summer have been very moderate to heavy and the incidence of CYSDV on spring melons was high on some late planted spring melons. How this translates into virus incidence on fall melons is not certain, but our experience suggests that you should anticipate risks from CYSDV to be as high as previous years. Further, given the aggressive management programs that PCAs and growers are now using, it will be interesting to see how CYSDV impacts melon production this fall. Our research to date suggests that fall melons produced near cotton or near areas where spring melons were recently produced are at the highest risk of infection. When possible, growers should attempt to isolate fall plantings as far away as possible from these sources of whiteflies and CYSDV. Growers forced to plant fall melons near these crops should be vigilant in minimizing adult whitefly infestation levels with insecticides during pre-bloom growth stages. To view a summary the status of CYSDV in Yuma County and guidelines for management visit2015 Guidelines for Whitefly and CYSDV Management on Melons. 

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 rain last week has raised many questions concerning its effect on the herbicides that are now being used for lettuce and cole crops. It will help some and hurt others. Kerb does not adhere to most of the soils here and more than about 0.7 inches of overhead water at one time can move it below the germinating weeds. Split applications are registered, and it may help to make an additional application although you are not supposed to go over the maximum total labelled rate. If you plan to go to a different crop that is sensitive to Kerb, it may be beneficial to do some tillage. Kerb works best when it is in a concentrated layer and this could bring some of the herbicide back up, but it will also help to dilute what is there.  Prefar, on the other hand, adherers strongly to most the soils here and the more overhead water the better. It is hard to apply too much water for Prefar. If going back to a sensitive crop, tillage will help. Balan, Prowl and Trifluralin all adhere to the soil and water will help incorporate them in most of the soils here. They adhere to the soil and once applied they are pretty much there for 3 to 6 months. Ponded water helps break them down and sometimes organic matter will tie them up. All 3 of these herbicides are normally mechanically incorporated and tillage will not help much if you need to minimize potential injury. GoalTender is a contact herbicide that works by creating a barrier that seedling weeds contact after germination. This herbicide can evaporate off of the soil surface following rain if there is excessive moisture followed by bright sunlight. Anything that breaks the herbicide barrier at or near the surface will reduce weed control but also increase safety to sensitive crops.

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:             
CEW moth counts are down areawide consistent with this time of year. 
 
Beet armyworm:         
Trap counts increased in most locations, and are about average compared to previous years.
 
Cabbage looper:           
Cabbage looper counts declined  all  traps, well below average for this time of season.
 
Diamondback moth:      
DBM moths counts have declined and well below average for this time of the year.
 
Whitefly:                      
Adult movement decreased in the past 2 weeks, and remains below average for this time of year. 
 
Thrips:                          
Thrips adults decreased in most locations with the exception of Tacna. Currently, below average for Novenber.
 
Aphids:                        
Aphid movement loght, but most active in in North Yuma Valley and Gila Valley. Below average for November.
 
Leafminers:                  
Adult activity up in a few locations, but well below average.