Historically, our Areawide Pheromone and Sticky Trap monitoring for insects was terminated around the first of April as the produce season ended. Beginning 4 years ago however, we continued our Areawide Trapping Network throughout the summer to collect trapping data from all 15 areawide trap locations year-round.  So why is this additional trapping data useful? For several reasons: 

1) Understanding the activity of some of our key pests when produce is not grown during the summer may give us an indication of what to expect as the fall produce season begins. This may be particularly helpful for predicting moth flights and whitefly flights in August-September coinciding with early transplanting and direct seeded crops.  Another example is keeping track of corn earworm which can unexpectedly show up near the beginning of fall harvests. 
 
2) Trapping for pests during the summer has shown us that 2 of our more important produce pests are not caught in traps during the summer. We presume this is due to the absence of brassica crops and weeds for diamondback moth, and high daytime/nighttime temperatures lethal to aphids. The fact that trap catches resume in the fall supports our conclusion that these pests are absent in the summer, only to reenter the desert via winds and/or transplants in the fall. And finally, 

3) It gives me something to do in the summer other than write reports and papers. 
So, visit the Areawide Summer Trap Network if you’re curious what our key pests are up to.

For those of us living in the desert, particularly working in agriculture, we commonly use rather affectionate terms to describe water.  Water is often referred to as the “life blood” of the desert and we know that “water is life” and it is the most critical limiting factor in any desert crop production system.  It is important for everyone in Arizona agriculture to be aware of our water supplies and the prospects for the future.  
 
As the population has grown in the desert Southwest, the demands on our water resources have increased substantially.  This has been exacerbated by two decades of drought and increasing average temperatures.  As a result, Arizona water supplies have become increasingly critical in terms of both short and long-term capacities. 
 
Continual reviews are being conducted by the Arizona Department of Water Resources (ADWR) and the Central Arizona Project (CAP) and other Arizona agriculture groups regarding Arizona water supplies, specifically from the Colorado River, which supports, at least in part, more than 80% of the Arizona population. The system-wide effort to stabilize the Lake Mead water supply with the 2019 Drought Contingency Plan (DCP) seems to be working as intended to help forestall drops in the reservoir’s levels.  However, it does not remove all risk of continually lowering water supplies in Lake Mead. 
 
The DCP for the lower basin of the Colorado River, below Lake Powell, is a set of shortage-sharing agreements among the Lower Basin States of Arizona, California, and Nevada.  The DCP augments the 2007 shortage-sharing agreements put in place by the states who are dependent on the Colorado River. 
 
On 16 August 2021, the Bureau of Reclamation declared that Lake Mead will be in a Tier One shortage level beginning 2022.  The elevation of the lake is and will continue to be below 1,075 feet above sea level.  As a result, Arizona will now be subject to significant cuts in water deliveries from the Colorado River based on Tier 1 reductions in water allocations, that are part of the DCP, and this will go into effect in January 2022 (Figure 1).  This will result in Arizona reducing Colorado River water use by 512,000 acre-feet (AF), or 18% of Arizona’s total allocation of 2.8 AF.  Tier 1 reductions primarily impact the CAP water allocations, which will be reduced by 30%.  Under Tier 1 reductions, agricultural CAP water allocations will be reduced by 65%, primarily affecting Pinal County agriculture.  Statewide municipal & industrial and tribal allocations will not be reduced under Tier 1 guidelines.  Yuma area water allocations will not be reduced under Tier 1.
 
We continue to monitor Lake Mead conditions and if lake levels drop to 1,050 and 1,045 ft., we will enter Tier 2 (a and b, respectively) conditions which will increase total reductions of Colorado River water to Arizona to 590,000 and then 640,000 AF, or 21 and then approximately 23% of Arizona’s total allocation.  The ADWR provides a good source of information and the prospects on these changing conditions.
 
Good management and stewardship of our water resources in the field is always important and we are particularly alert to that now.
 
For additional information please refer to the ADWR, CAP, BOR, and the University of Arizona Water Resource Research Center websites:
https://new.azwater.gov/
https://www.ibwc.gov/Files/CF_CR_LBDCP_073019.pdf
https://library.cap-az.com/documents/departments/planning/colorado-river-programs/CAP-FactSheet-DCP.pdf
https://www.cap-az.com/
https://wrrc.arizona.edu/

Figure 1. Colorado River water reductions in 2022 for CAP users after DCP
mitigation.  Reference: Arizona Department of Water Resources (ADWR) and the
Central Arizona Project (CAP).

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%). Variety: Deluxe (HMX2595) was seeded, then sprinkler-irrigated to germinate seed on March 20, 2024on 84 inches 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. 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. 

Spray treatments were done on 05-21-2024, 05-31-2024, 06-07-2024 and 06-14-24. Powdery mildew was first seen on 06-05-24. Please see excel file for additional details.  

Disease severity of powdery mildew (caused by Sphaerotheca fuliginea and S. fusca) severity was determined 6-17-2024 by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 1 = one to two mildew colonies on leaves  ;2 = powdery mildew present on one quarter of leaves; 3 = powdery mildew present on half of the leaves; 4 = powdery mildew present on more than half of leaf surface area ; 5 = powdery mildew present on entire leaf. These ratings were transformed to percentage of leaves infected values before being statistically analyzed.

The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. Most treatments significantly reduced the final severity of powdery mildew compared to nontreated plants. Quintec, Merivon, Tesaris, Luna Sensation, and V6M-5-14 V gave the best disease control. Phytotoxicity symptoms were not noted for any treatments in this trial.

ANR Webinar 10/17 click link for details.

Yesterday, we initiated our first trial of the season examining the use of band-steam for controlling Fusarium wilt of lettuce. The premise behind this research is to use steam heat to raise soil temperatures to levels sufficient to kill soilborne pathogens. For Fusarium oxysporum f. sp. lactucae, the pathogen which causes Fusarium wilt of lettuce, the required temperature for control is generally taken to be > 140°F for 20 minutes.

In our multi-year study, we are using a 35 BHP steam generator mounted on a custom designed elongated bed shaper to inject steam in the soil (Fig. 1). Trials conducted last fall show the technique holds promise. Fusarium colony forming units (CFU) were reduced from 2,600 in the control to 155 in the 0.75 mph travel speed and 53 in the 0.5 mph travel speed treatments, respectively (Fig. 2).

Fusarium load at the site where this week’s trial was conducted is reportedly high and we’re looking forward to obtaining good results. We’re also planning a second trial later this month at the Yuma Ag Center that is also focused on Fusarium wilt of lettuce control.

Stay tuned for results of all our trials examining the efficacy of using steam heat to control Fusarium wilt of lettuce, sclerotinia lettuce drop, pythium and weeds.

As always, if you are interested in seeing the machine operate or would like more information, please contact me.

Acknowledgements
This project is sponsored by USDA-NIFA and the Arizona Specialty Crop Block Grant Program. We greatly appreciate their support. A special thank you is extended to Larry Ott and Gila Valley Farms for allowing us to conduct this research on their farm. Fig. 1. Prototype band-steam applicator/bed shaper operating in Wellton, AZ. Fig. 2. Effect of band-steam applied at two travel speeds on Fusarium colony forming units (CFU) in the soil.

Fig. 1. Prototype band-steam applicator/bed shaper operating in Wellton, AZ.


Fig. 2. Effect of band-steam applied at two travel speeds on Fusarium colony
forming units (CFU) in the soil.

It is common to keep produce fields clean only to find a carpet of purslane when preparing ground for the next season. Some of this is from the seed bank that hadn’t yet germinated or been blow or carried into the field but a significant amount comes in the water. We recently worked with Brad Chavez from Greenline Equipment and Jim Nunes from Nunes Farms to test an irrigation water filter system designed GLE to filter the smallest weed seed. We have tried various techniques for filtering weed seed over the years and were surprised by how well this system worked. We injected alyssum seed into a sprinkler system on a 17 acre field in the Gila Valley. The field was divided into 2 acre plots and half of them were irrigated with filtered water and half were unfiltered. Alyssum seed supplied by Select Seed is 0.5 mm to 0.75 mm in diameter or the same size as purslane seed. We recovered 86% of the filtered seed that was injected through the system in the filters and were unable to find any alyssum plants in the filtered plots compared to 136 seeds/ sq. ft in the unfiltered plots. This system won’t clean up a field in one season but can eliminate a significant source of weed seed and significantly reduce weed problems when used over a period of years.
Please click on the following link for more information on the Weed Seed Filtration Systems.

This technology was developed by Greenline  Equipment and has a PATENT
PENDING  for G-PAWDS™️ PORTABLE AUTOMATED WATER DELIVERY SYSTEM.

 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.