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 Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Lettuce was seeded, then sprinkler-irrigated to germinate seed on Nov 28, 2023 on double rows 12 in. apart on beds with 42 in. between bed centers.  All other water 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 Jan 4, 2024  at the 3-4 leaf stage to a 12-inch spacing. Treatment beds were separated by single nontreated beds. Treatments were applied with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart.

Month	MaxTemp(°F)	Min Temp (°F)	Average Temp (°F)	Rainfall
November	80	51	65	0.08 in
December	71	44	57	0.82 in
January	68	42	54	1.14 in
February	73	47	59	0.50 in

 
Downy mildew (caused by Bremia lactucae) rating was done on variety Eblin, Bobcat, and 180 (partially funded by AILRC grant). Disease was first seen on 1-30-24. Please see attached excel file for chemicals application date. Disease rating was done on February 29^, 2024. Disease severity was determined  by rating 10 plants within each of the five replicate plots per treatment using the following rating system: 0 = no downy mildew present; 0.5 = one to a few very small downy mildew colonies on bottom leaves; 1 = downy mildew present on bottom leaves of plant; 2 = downy mildew present on bottom leaves and lower wrapper leaves; 3 = downy mildew present on bottom leaves and all wrapper leaves; 4 = downy mildew present on bottom leaves, wrapper leaves, and cap leaf; 5 = downy mildew present on entire plant.
The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. Most of the treatments exhibited activity against the disease to some extent. Latitude, Amara, Eject, Previcure flex exhibited good control in the variety Eblin (highly susceptible variety). Whereas Cevya, Stargus, Latitude, Amara, Revus, Thrive 4 M, Actigard, Instigo+Carbose+intereact showed activity against the pathogen in variety Bobcat. Please see excel file for the full list of chemicals and their efficacy. The lettuce variety 180 was resistant to the disease and no downy mildew was observed on the particular variety. No phytotoxicity was observed in this field.

Grass weeds are, in general, more of a problem during the summer than they are at other times of the year. There are more than 25 annual grass species that are found here during the summer although only about 10 are common. Most of these look very similar at early growth stages and identification can be difficult. There is a tendency to lump them all together and call them water grass, jungle rice barnyard grass or several other names. There are differences between them, however, and it is important to accurately identify them at early growth stages. This is important because many of them respond differently to herbicides and have different growth habits. For example, sprangletop is only controlled by the highest rates of Select (clethodim) and generics of this herbicide and missed by all of the other selective postemergence herbicides like Poast and Fusilade and sandbur is tolerant to all of them. By the same token, sandbur and sprangletop can over winter, come back from crowns and not be controlled by preemergence herbicides applied in the spring while most other summer annual grasses die in the winter and the seed can be controlled with herbicides in the spring. There are just 6 genera and 12 species of summer annual grass that are common here. These include echinochloa (water grass and barnyard grass), leptochloa (red sprangletop and mexican sprangletop), eriochloa(southwestern cupgrass and prarie cupgrass) , cenchrus (field sandbur and red sandbur), setaria (green foxtail and yellow foxtail), and chloris (feather finger grass and truncate finger grass). A power point presentation can be found by clicking on Summer Annual Grass ID which contains pictures and descriptive characterics of each of these species.

Area wide Insect Trapping Network   VegIPM Update, Vol. 12, No. 15, Jul 28,  2021
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts decreased significantly since mid-June comparable to what we observed last summer.
 
Beet armyworm:         
Trap counts remain low in most locations  and are trending similar to last summer.
 
Cabbage looper:         
Cabbage looper numbers remain low consistent with the lack of activity this fall and summer compared to last season.
 
Whitefly:                     
Adult movement continuing to increase rapidly, particularly in Wellton and Dome Valley consistent with the termination of spring melons.
 
Thrips:                          
Thrips adult movement continuing to decline to numbers comparable to this time last year.
 
Aphids:                        
Aphid movement has been absent for the past 2 months typical with high summer temperatures.  
 
Leafminers:                 
Adult activity slightly above for mid-summer.
 
Diamondback moth:    
DBM trap counts have been zeroed out in all trap locations for all of July consistent with trends observed over the past 5 years.