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. 

The drought-related pressures on the Colorado River system that have been impacting the entire basin and region for 23 years have slackened briefly due to the wet winter in 2023 that included a good snowpack in the mountains, better rainfall throughout the basin, and improved flows into the river.  The current water level at Lake Mead on Hoover Dam is 1,068.25 ft. above sea level on 3 January 2024.  That level is 160.75 ft below full pool of 1,229.00 ft. (Figure 1).

 

In mid-December 2023 representatives from each of the seven Colorado River Basin states met in Las Vegas, NV during the annual Colorado River Water Users Association conference.  The focus of current discussions among the basin states is to negotiate a new compromise for the guidelines of use under conditions of water shortage.  These new guidelines will go into place at the end of 2026.  The immediate goal is to draft proposals by March 2024.
 
The negotiations are incentivized by having the opportunity for the post-2026 guidelines being developed by the basin states themselves as opposed to litigation or legislation.  A major concern driving this process among the basin states that basin state representatives should be able to do this better than turning the process over to people and entities that have less direct familiarity with the situation and no real “skin” in the game.  
 
The 1963 decision by the Supreme Court of the United States in of the Arizona v California case directed the federal authority on the management of the Colorado River to the Department of the Interior and the Bureau of Reclamation (BoR).  However, the basin states have the chance to negotiate their future management plans on the Colorado River.  If they fail to do so in the allotted time, the process will be managed by the federal government.  
 
The basic water budget challenge is based on the following basic statistics:
 

• The current water budget on Colorado River allocations is 16.5 million acre-feet (maf)/year.
• Average annual flow on the Colorado River from 1906-2017 was 14.8maf/year.
• The average annual flow between the years 2000 - 2018 has been approximately 12.4maf/year.
• That is 16% lower than the 20^th century average flow.
• It is estimated that 1.5 maf/year is lost due to evaporation and system loss.
• Thus, the 4 maf/year target reduction that has been identified by the BoR is basically the difference between the 16.5 maf/year allocated versus the 12.4 maf/year average flow in the first two decades of this century.

 
Some notable progress is being made for conservation of Colorado River water with agreements among lower basin states and tribes that will conserve more than 1.5maf/year through 2026.  For example, California water agencies have recently agreed to conserve up to 643,000 acre-feet/year through 2025.  The Quechan Indian Tribe has reached an agreement with federal water managers to save up to 39,000 acre-feet/year through 2025.  Arizona has agreed to conserve up to 348.00 acre-feet/year through 2026.  All these temporary agreements are being supported with federal funding.
 
With agriculture responsible for 70% of the diversions on the Colorado River, these negotiations are extremely important for the future of agriculture in this region and our capacity to support high population densities that are now common and rapidly growing.
 
These types of negotiations are certainly challenging in dealing with a limited water supply and a lot of demand.  There are many competing interests involved.  Yet, we are confident that the representatives we have will be able to work this out and come to a set of functional agreements.

Though sunflower is not a major crop in Arizona, it is one of the common ornamentals grown in home gardens. We have been witnessing some sunflowers in the area with the disease. It is also important to know about the diseases in sunflower as Arizona is home to large population of wild sunflowers.  
 
Several species of the genus Rhizopus have been implicated in causing head rot, including R. arrhizus A. Fischer, R. stolonifer (Ehrenb.:Fr.) Vuill., and R. microsporus Tiegh. It has historically been considered to be of minor importance, however, it was documented as causing severe losses in Israel, and a recent survey of sunflower diseases in California found that Rhizopus head rot was the most common disease of sunflower. Under favorable conditions, it caused 100% losses in certain field. Infection is initiated in heads through wounds created by hail, birds, or insects.
 
Symptoms first become noticeable as dark spots on the back of ripening heads, followed by a watery soft rot that later turns brown. As disease progresses, heads dry prematurely, shrivel, and tissues appear to shred. Inside shredded tissues, coarse, thread-like mycelial strands are observed, followed by the appearance of small black dots (sporangia). Sporangia are filled with spores that are easily released and wind-blown to other plants. Symptoms on the flower side of heads include the appearance of mycelium, a grayish, fuzzy substance that is covered with sporangia (Fig 1-7) 
 
Some type of mechanical injury on the head in combination with high temperatures and high relative humidity are required for infection and disease progress. Damage and economic losses are dependent upon time of the season that wounding and infection occurs. Infection rarely occurs before flowering, and greatest yield reductions result when infection occurs before seeds are properly filled. Infection in Israel has been primarily attributed to wounds from bird feeding. In the US High Plains, disease is initiated through head moth infestations and severe storms with hail.
 
Disease problems can be reduced by controlling the head moth at or before flowering, and by avoiding mechanical wounding after flowering. If you are growing sunflower commercially, it is also important to rogue or control volunteer and wild sunflowers before they produce seed; they may serve as a reservoir for insects and the Rhizopus.

Fig 1: Symptom of Rhizopus head rot on sunflower


Fig 2-7 Source: https://extensionpublications.unl.edu/assets/pdf/g1677.pdf

More information: 
https://cropwatch.unl.edu/plantdisease/sunflower/rhizopus-head-rot
https://extensionpublications.unl.edu/assets/pdf/g1677.pdf

Time flies. February is right around the corner and that means it is farm equipment/ag trade show season. Upcoming regional events include the World Ag Expo, Tulare, CA, February 13-15, the Southwest Ag Summit, Yuma, AZ, February 20-22, and AgroBaja, Mexicali, Mexico, March 7-10.  If you are interested in the latest ag tech and farm machinery, all are outstanding events and well worth attending. For more information, click on the links below.

Fig. 1. Upcoming farm equipment/ag trade show events: World Ag Expo, Tulare,
CA, February 13-15, 2024 theSouthwest Ag Summit, Yuma, AZ, February 20-
22,2024 and AgroBaja, Mexicali, Mexico, March 7-10, 2024.

Before making decisions for weed control it’s imperative to have a proper identification of the plant species. There are two names for plants:
The common name, which is a name that people come up with in a certain region to describe a particular weed and it varies by region and therefore can be confusing. Then we have an exact scientific name for each species that is based in the binomial nomenclature system started by Carl Linnaeus in 1753. This binomial (or two term) system includes the genus and the species, which is used worldwide¹.
 
Some very close species from the same family can be controlled by the same product but occasionally their herbicidal susceptibility varies. Such is the case of Chenopodium murale (goosefoot) and Chenopodium album (lambsquarter) two very close and similar species. A product like Pursuit (Imazethapyr) has good activity on goosefoot but can’t control lambsquarters. With accurate identification in a mixed population, you would be able to determine what strategy to use or select the herbicide that would control both species. 
 
There are about 75 weeds most common in Arizona and are included in the PCA² study guide, but many other species could be introduced to the State and complicate our crop production systems. Two great tools for weed identification are the books “An Illustrated Guide to Arizona Weeds” that lists 172 species, and “Weeds of California and Other Western States” which has at least one photograph of 735 weeds.
Another weed identification tool is the book “Weeds of the West”.
Additionally, there are many phone applications that can be used as identification tools such as “id weeds”, “PlantNet”, “PictureThis”, “iNaturalist”, “Seek”, “PlantSnap” and “LeafSnap”. When we have problems with weed ID we contact the UA herbarium.
Thank you for sending samples for Weed ID to the IPM Team it is always a learning experience.

 Areawide Insect Trapping Network   VegIPM Update, Vol. 15, No. 16, Aug 7, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts decreased areawide; about average to previous years.
 
Beet armyworm:        
BAW moth counts decreased; comparable to previous summers.
 
Cabbage looper:         
Cabbage looper numbers are low consistent with previous years and higher temperatures.
 
Diamondback moth:     
DBM moths were not caught in any trap; average for this time of the year.
 
Whitefly:                     
Adult movement continues to decrease, average for this time of the year.
 
Thrips:                          
Thrips adult activity continues to decline, average for early August.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                   
Adult activity declining and below average for early August.