Foxglove Aphid: Foxglove aphid have been found colonizing lettuce here at the Yuma Ag Center. This is not unusual considering this aphid species tends to be more biologically active under warmer temperatures. However, foxglove aphid is important because it has a tendency to colonize on younger leaves. This often translates into contamination of the heads or hearts of iceberg lettuce, romaine and celery. The key to effective foxglove aphid (and other aphids as well) management with foliar insecticide is to initiate sprays at the time apterous (wingless) aphids begin to colonize. Of course, this requires diligent scouting and sampling. On older lettuce, make sure you thoroughly examine developing heads/hearts. Fortunately, PCAs have alternatives for foliar aphid control. For more information on insecticide alternatives please visit the Foxglove Aphid on Desert Lettuce Crops.

Corn Earworm: We’re beginning to catch corn earworm moths in pheromone traps throughout the area. This is significant since we had not previously caught any earworm since early November. Trap catches have been high in the Gila Valley over the past 2 weeks (see Areawide Trapping Network). This could be an early indication of egg deposition in fields which is important because once head formation begins, larvae will typically bore into the head 1-2 days upon hatching. They are much more likely to bore into lettuce heads than other Lepidoptera larvae. Larvae may enter the head from any point, although recently we’ve observed them burrowing in from the base of the plant near the core. If fields are not watched closely, infestations may not be noticed until the head is harvested. Once inside the head, it is almost impossible to control the larvae with insecticides.

Mystery Lepidopterous Larvae: An unidentified lepidopterous larvae has been found burrowing into the roots of young romaine plants in the Yuma Valley. Several PCAs have reported this larvae and damage over the past 2 weeks when finding romaine plants wilting in the field. When plants were removed and examined, the damage and larvae could be found near the base of the plant. Images of the damage and larvae can be found in the attached document Mystery Larvae. We have reared one of the larvae and waiting to have the adult moth identified to species. If anyone has seen this larvae in the field please contact us, as we would like to collect more larvae for further identification.

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.

Wheat is commonly grown following lettuce that was treated with soil active herbicides. The most commonly used lettuce herbicides are Balan (benefin), Kerb (pronamide) and Prefar (bensulide). All 3 of these are root and shoot growth inhibitors that effect grasses and slight and temporary injury to wheat is not uncommon. Yield lose is rare. Wheat is a fairly large seeded grass that is vigorous enough to overcome some injury. Two herbicides, trifluralin (Treflan) and pendimethalin (Prowl) that have this same mode of action are registered for use on wheat in some states. Where trifluralin is used, the wheat is normally planted below the treated soil. Pendimethalin is used here on wheat after it is established and has a good root system. It is often used safely preplant  where the wheat is planted deep enough to avoid contact with the herbicide. All of the lettuce herbicides are normally put on during crop establishment and have had at least 3 or 4 months to dissipate. Persistence of Balan, Kerb and Prefar is variable but is normally 2 to 6 months. When these herbicides are applied in a band, it is often possible to see some stunting in this band at the early stages of the wheat crop. Wheat will normally outgrow this.

Area wide Insect Trapping Network   VegIPM Update, Vol. 14, No. 22, Nov 1, 2023            

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth captures have steadily decreased over the past 2 weeks, and areawide about average for late-October.
 
Beet armyworm:         
Trap counts reached their highest levels so far this season, particularly in Tacna, Wellton and Yuma Valley, and about average for late October.
 
Cabbage looper:           
Cabbage looper numbers decreased areawide, and are still below average for this time of the year.
 
Diamondback moth:   
Sporadic DBM activity in low numbers throughout the area, trending well below average for late October.
 
Whitefly:                      
Adult movement increased in the past 2 weeks and above average for late October.
 
Thrips:                           
Thrips adult activity peaked in the last two weeks, and trending below average in October.
 
Aphids:                        
Winged adults continue to be captured for the season, consistent with heavy winds from W-NW. Aphid captures thus far have been well below average. 
 
Leafminers:                  
Adult activity decreased in most areas, and trending about average for late October.