We are beginning to observe winged (alate) aphids appearing on desert lettuce and cole crops, but proper identification of winged aphid species found on leafy vegetables in the desert is important for cost-effective pest management. Most of the important aphid species we find on local crops do not over-summer here because of high temperatures and lack of viable hosts. Thus, winged aphids typically begin migrating onto desert crops beginning in late October-early November, often being blown in with the gusting winds. My experience over the past 20 years suggests this is due in part to cooler weather more favorable for their behavior and development, as well as changes in prevailing winds that now begin to blow into the area from the north and west. Consequently, once the aphids reach our desert valleys, they typically move from crop to crop until they find a suitable host to feed and colonize on. It is not uncommon to find winged aphids on lettuce or broccoli that are specific pests of small grains (i.e., corn leaf aphid) or alfalfa (i.e., pea aphid). Because these aphid species will not colonize lettuce, it is important to be able to distinguish them from the key aphid pests commonly found on lettuce that do colonize and require management to prevent problems at harvest (green peach aphid, foxglove aphid, lettuce aphid). Also, you are likely to find cowpea aphid in lettuce as it can be common in alfalfa at this time. However, experience has shown us that although small cowpea aphid colonies may be found on lettuce, the populations rarely increase in lettuce crops. The bottom line: proper aphid identification can save a PCA time and money, and prevent unnecessary insecticide applications. A simple pictorial key provides provides information that can assist PCAs with identifying winged aphids. important in lettuce and other leafy vegetables.

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.

Stay tuned for more on this highly effective technique for controlling soilborne pathogens and in-row weeds. Traditionally the entire soil bed profile is treated which is energy intensive... cost prohibitive?...Check out video below:

The volatility of herbicides, or the change from a solid or liquid to a gas, is dependent on several environmental factors and is extremely variable. We have been working on finding a replacement for Glyphosate for non-crop weed control and have tried to determine the stability of the potential  herbicide alternatives. There are various methods used to measure herbicide volatility. All herbicides are initially tested in the laboratory to determine volatility and other properties. Volatility is specifically measured by placing a given volume of herbicide in a container, exposing it to various temperatures and humidity’s and then weighing how much is left. This is done under very controlled conditions. Another technique that is often the next step is to conduct bioassay studies in a greenhouse. This usually involves placing a container with the herbicide spray solution in a closed environment with sensitive plants. Injury to the bioassay plants are measured visually or by some other means.  Field Studies are often conducted to measure herbicide volatility. This technique is the most applied, but the results are often imprecise and variable depending on environmental conditions. This commonly involves spraying an isolated area in the field and after the spray has settled placing sensitive plants at variable distances and directions away. Injury is observed or measured at variable time periods. We used this technique on June 10 to June 15 this year at the Yuma Valley Agriculture Center to measure volatility of 13 herbicides we are evaluating as alternatives to Glyphosate. Seven X 10 Ft. plots were sprayed, and tomato plants were placed 25Ft. away from each sprayed area on the north, south, east and west corners 1 hours after application A 50 Ft. buffer separated each sprayed plot. Visual injury was measured to the tomato plants at 24 and 48 hours after they were placed in the field. The 13 herbicides were used in this trial included 5 modes of action and are listed below.

The temperature reached above 100 F, the humidity was 10 to 20% and wind was 5 to 10 MPH during the trial. No injury symptoms were observed to any of the tomato plants from any of the herbicide treatments. The trial included low volatility formulations of the plant growth regulators, 2-4-D (Embed) and Dicamba (Enginia) which are often volatile under these hot and dry conditions. Neither of these two, or any of the other included herbicides, moved 25 ft or more in this one trial. We know, however, that in other trials the results have sometimes been different. Volatility is variable and difficult to measure in field trials.

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 4, Mar 1, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts remain  low levels  in areas, below average for this time of year.
 
Beet armyworm:          
Trap counts low; increased areawide; lower than average compared to previous years.
 
Cabbage looper:          
Cabbage looper counts increased in most traps and below average for this time of season.
 
Diamondback moth:      
DBM moth counts increased significantly in  Gila and Yuma Valley. About average for this time of the year.
 
Whitefly:                     
Adult movement negligible, average for late winter. 
 
Thrips:                          
Thrips adult counts increased in most areas, below average compared with previous years.
 
Aphids:                         
Aphid movement increased in many in the Yuma and Gila Valleys; above average for early March.
 
Leafminers:                   
Adults remain low in most locations, average for late- February.