Summer is finally over. Brassica transplants are in the ground, and direct-seeded broccoli and lettuce plantings are now beginning.  In the past week, I’ve observed or received reports from PCAs of key insect pests beginning to show up (or not) on melon and early produce crops in the desert.   
 
Seedling pests:  Flea beetles (FB) are beginning to show up in transplanted crops like they always do, but pressure has been light so far. We haven’t seen much in our experimental plots at YAC either.  Remember, FB adults lay eggs in the soil of their favored local host plants (i.e., alfalfa, cotton, purslane, pigweed and nightshade) where larvae feed on the roots to later emerge as adults. So, keep in mind, the source of that FB infestations hitting your new stands may not just be freshly cut hay, defoliated cotton, or disked weeds. In some areas (Yuma Valley), crickets seem to be very abundant. Crickets like moisture and are often found under sprinkler pipes but can also be found in cracks in soils around fields or in drainage areas. 
 
Bagrada bug:    We’ve already had reports of bagrada bug adults on two transplanted cauliflower fields in Dome Valley. Not sure whether they arrived with the transplants or are moving from surrounding crops. However, it’s still early and they might surprise you as the season progresses.   Look for those fresh feeding signs on cotyledons and young leaves.  Experience suggests that they are most abundant after the humidity breaks.
 
Lepidopterous Larvae (worms):   Worm pressure seems to be below normal. Trap catches so far show that Cabbage looper moths are almost non-existent, and no reports on melons to date. They should pick-up as we approach October. No reports of Beet armyworm larvae on the earliest transplants yet, and areawide pheromone traps suggest that moth activity is below normal. But they will show up sooner or later, so get ready.  You have numerous insecticide alternatives at your disposal to control them.  Have had a couple of reports of Diamondback moth larvae on newly transplanted brassica crops. However, we’ve yet to capture moths on pheromone traps which suggests that adult immigration on high altitude winds associated with storms has not occurred. Remember, DBM disappear each summer and reestablish on desert crops via transplants or migrate in on monsoon/tropical storms. I strongly stress that you check your Cole crops closely this fall, particularly following storms or on plants originating from coastal CA. 
 
Whiteflies:       Area wide sticky trap captures have been about normal for early September, but whiteflies can migrate long distances on high winds. Adult numbers increased on my melon plants last week and remain high. Reports in area melons range from light to moderate numbers so far, but there is still a lot of cotton out there yet to be picked. The good news is there are several insecticide alternatives to control them in produce. 

This study was conducted at the JV farms at Gila Valley. Lettuce variety ‘Guapo’ was seeded, then sprinkler-irrigated to germinate seed on September 19, 2023, on double rows 12 in. apart on beds with 42 in. between bed centers.  Rest of the irrigation was supplied by furrow irrigation or rainfall. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of 25 ft of bed, which contained two 25 ft rows of lettuce. Plants were thinned on October 9, 2023 at the 3-4 leaf stage to a 12-inch spacing. Treatment beds were separated by single nontreated beds. Treatments were applied by incorporating in soil before seeding or with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart.

Month	Max	Min	Avg	Rain
September	100	71	86	0.71 in
October	93	61	77	0.00 in
November	80	51	65	0.08 in
December	71	44	57	0.82 in

 
Fusarium wilt (caused by Fusarium oxysporum f. sp. lactucae ) rating was done in the field by observing the typical symptom of lettuce wilt. Confirmation was done by cutting the cross section of roots. Disease scoring/rating was done on December 6, 2023. 
 
The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. The disease pressure was extremely high in 2023, and most treatments showed little or no control against the disease. The treatments that showed some activity were Bexfond, Cevya, Rhyme, and Serifel. Plant vigor was normal and phytotoxicity symptoms were not observed in any treatments in this trial.

Some of the oldest and most effective broadleaf herbicides are the growth regulators. These include 2,4-D (Several names 2,4-DB (Butyrac, Butoxone), MCPA (Rhomene Rhonox, Chiptox, Battleship & others), Dicamba (Clarity, Banvel), Clorpyrolid ( Stinger), Triclopyr (Garlon, others), and many products containing 2 or more of these. Their principle use in this region are on grain, bermudagrass, alfalfa, cole crops and sugarbeets. Their utility is very limited in this region, however, because of their volatility and potential to move and cause injury to sensitive crops. 

Volatility is very different than spray drift. Spray drift is the airborne movement of the herbicide to non-target sites. It is often related to physical conditions like wind speed, nozzle type and pressure, application technique and other factors. Volatility, on the other hand, involves movement after the herbicide has evaporated into the air as a gas. It is affected not only by physical conditions but more importantly by characteristics of the herbicide including chemical properties of the active ingredient, especially vapor pressure, and formulation type. All of the growth regulators have high vapor pressure and are volatile. These herbicides can be formulated differently and formulation can significantly affect volatility. The amine formulations are much less volatile than the ester formulations of all of these products. The amount of product used can vary with formulation and there is generally more volatilization potential with higher use rates. The type of salt used with the amine formulations are also influential. Formulations of Dicamba that use sodium salt ( Distinct, Celebrity Plus and Northstar) or diglycolamine salt (Clarity) are less volatile, for instance, than formulations using the DMA salt used in Banvel.

The volatility of all of these growth regulators is always higher during the hot summer temperatures. Their use is restricted in some counties in California between March 15 and October 15. Questions come up every year at this time about how long after application these products can volatilize and how far they will move. You can find information that claims everything from that they are safe after drying to that they can volatilize 60 days after application. Many of us have seen them not move at all at times and move a mile or 2 at others. This is likely because volatility is affected by so many factors. It will always be difficult to predict. 

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 have declined since early Nov and remain steady in most areas and about average for early December.
 
Cabbage looper:          
Cabbage looper has been increasing in Tacna and Dome Valley, but are still below average for this time of the year.
 
Diamondback moth:   
DBM moth counts increased in most locations over the past 2 weeks, trending below average for late December.
 
Whitefly                       
Adult movement continues to decrease in all areas and about average for early December.
 
Thrips:                          
Thrips adult activity slightly decreasing, and trending below average for late fall. 
 
Aphids:                        
Winged adults peaked last week following winds out of the W-NW. Aphid captures above average for early December. 
 
Leafminers:                  
Adult activity decreased in most areas, and trending about average.