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 is the second time we ae publishing the article in the newsletter this season. The reason being more and more fields showing symptom of the disease. In early season the disease is more of a concern in the greenhouse, and later in the season we see the disease in the field. Black rot is a disease in cole crops caused by bacterium, Xanthomonas campestris pv. Campestris.
 The pathogen can enter the field on transplants or seeds, and can stay in the soil for over a year where it survives on debris and weeds in the Brassicaceae family. The bacteria move primarily with water and can enter the plant through pores naturally present on the leaf surface. It can also be spread by workers and equipment moving through the field/greenhouse, and can enter the leaves through damage caused by wind, insects and other mechanical injuries. The bacteria need a temperature of 77 degrees and above. While it may seem like the weather in desert is not humid enough for bacteria to become an epidemic, it is not something that should be ignored. The microclimate in the field with the crop canopy being dense, foggy mornings, increased field activity can be conducible for disease development. 
Disease management include getting rid of infected plants/tissue, increasing distance between fields and choosing well-drained, controlling weeds especially in mustard family such shepherd’s purse, wild mustard, pepper weed etc.  Soil fumigation is effective but may not be economically feasible. Best management practice starts with disease-free seed; hot water treatment can reduce the likelihood that the bacteria will enter the field through the seed. Starting with healthy transplant is equally important. For diagnosis, you can bring the samples to the clinic or you can also do visual/field diagnosos. You will see patches of dead tissue in plants with blackened veins. Usually when the disease is systemic, you can see the black streak when you cut crosss section of the stem (see picture below).

It is better to be a month early when applying preemergence herbicides for summer annual grass control than it is to be a day late. They have begun to emerge so don’t wait. It is important to know which grass(s) that you have but that is not possible without prior knowledge when making preemergence applications. 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 prairie 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 characteristics of each of these species.

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 20, Oct 2, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:             
CEW moth counts low in most traps; below average for this early produce season. 
 
Beet armyworm:         
Trap counts decreasing in most areas, and below average for late September
 
Cabbage looper:          
Cabbage looper trap counts low in all locations, typical for mid-late September.
 
Diamondback moth:   
Adult activity beginning to pick up in Dome Valley.  Overall, typical of late September with minimal monsson activity.
 
Whitefly:                       
Adult movement most active in Dome Valley; overall below average for mid September
 
Thrips:                          
Thrips adult movement light; overall activity typical for September. 
 
Aphids:                        
Aphid movement absent so far; anticipate activity to pick up when winds beginning blowing from N-NW. 
 
Leafminers:                  
Adult activity light in all areas, about average for this time of season.