Historically, our Areawide Pheromone and Sticky Trap monitoring for insects was terminated around the first of April as the produce season ended. Beginning 2 years ago however, we continued our Areawide Trapping Network throughout the summer to collect trapping data from all 16 areawide trap locations year-round.  So why is this additional trapping data useful? For several reasons. First, 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. Secondly, 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, it gives me something to do in the summer.  So, visit the Areawide Summer Trap Network if you’re curious what our key pests are up to. We also continue to monitor thrips activity during the summer. This involves plant sampling using a dislodgement sampling method (beat pan) to determine the relative abundance of thrips adults and larvae on alfalfa, cotton, melons, wheat, Sudan grass, and weeds.  This is being conducted to supplement our yellow sticky trap data that only indicates thrips adult flight movement an area. With this plant sampling we should be able to determine the primary host plants thrips are colonizing in the cropping season during the long hot summer. We are also trying to determine whether these crops allow for the reproduction of thrips. So far, all the crops and weeds we have sampled have shown that thrips will reproduce and complete their life cycle on them. This is important, particularly for weeds, as we are trying to determine whether INSV can be survive the summer in the absence of lettuce. It is also important because it allows us to determine potential exposure of thrips to key insecticides like Radiant and Lannate for resistance management purposes. These crops essentially serve as untreated refugia that likely sustains insecticide susceptibility and is the reason these products are still effective against thrips.  We will be conducting this work throughout the summer, as well as through next produce season. We will periodically provide updates of these thrips monitoring results throughout the summer.  As my dad used to say, “to solve the problem, you must first understand the problem”.

On Tuesday, 15 August 2023 officials from the U.S. Bureau of Reclamation (USBR) presented their 24-Month study reports with projections and operational plans for 2024 (USBR, 15 August 2023).  We are still dealing with the drought but there is some improvement in the 2024 plans for Colorado River water allocations for Arizona.
 
The wet winter and spring experienced in the Southwest in 2023 has provided some relief on the dire situation we were facing on the Colorado River system and reservoir levels have improved.  But unfortunately, one good precipitation season does not solve all the problems and they will still need to be dealt with.
 
The current plan for lower Colorado River water management is basically a return to the Drought Contingency Plan (DCP) Tier 1 schedule (Figure 1).  

Fgure 1.  Drought Contingency Plan Tier reductions for Arizona.

Tier 1 plans take us back to an 18% reduction or 512,000 acre-feet (KAF) of Arizona’s Colorado River allocation of 2.8 million acre-feet (MAF).  Arizona was operating under Tier 1 guidelines in 2022.  
 
The irrigation districts in central Arizona that have lost access to Central Arizona Project (CAP) water will not be receiving any additional water in 2024 based on this plan.  The districts immediately adjacent to the mainstem of the Colorado River will continue to receive the same amount of water as they have been receiving the past two years.  For Arizona and the other lower basin states, these are basically the same water allocation guidelines that were in place in 2022.
 
The urban areas and American Indian tribes will not experience any additional reductions based on the USBR plans. However, some cities and tribes have volunteered to reduce their Colorado River water allocations in exchange for payments from the federal government.
 
For example, in 2023 Arizona, California, and Nevada agreed to a plan that will conserve an additional 3 MAF of Colorado River water through 2026 in exchange for $1.2 billion from the federal government.  If approved by the USBR, this plan would reduce Colorado River allocations to the Imperial Irrigation District in California, which has some of the most senior water rights on the river.
 
The Gila River Indian Community (GRIC), which has a Colorado River allocation of 653 KAF, committed in April 2023 to relinquish temporarily 125 KAF in exchange for $400 per AF from the federal government.  The federal government is also funding GRIC infrastructure projects to increase wastewater reuse in irrigation.
 
Thus, some of the Colorado River water that is technically allocated to Arizona under Tier 1 guidelines will stay in Lake Mead due to previously agreed upon conservation measures.
 
Regarding other lower basin states and the current USBR plan, Nevada will have slightly more Colorado River water in 2024 than in 2023.  Mexico will deal with a 5% reduction in Colorado River water from their base and once again California will not be suffering any required cuts in their Colorado River water allocation.
 
Overall, this is good news.  We have some temporary relief on the Colorado River system and no additional reductions will be required in 2024.  This puts the seven Colorado River basin states and Mexico in a better position to negotiate the guidelines and agreements required for 2026 since all the existing agreements expire in two years.
 
Reference
 
USBR, 15 August 2023. 24-Month Study reports.   

• 24-Month Study Projections (Overview)
• August 2023 Most Probable  
• August 2023 Probable Minimum 
• August 2023 Probable Maximum   

August 2023 Lake Powell and Lake Mead: End of Month Elevation Charts

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.

Mark C. Siemens, Department of Biosystems Engineering
Vol. 14, Issue 16, Published 8/9/2023
Pre-Season Vegetable IPM Workshop
Mark C. Siemens
Vol. 14, Issue 17, Published 8/23/2023

The Pre-Season Vegetable IPM Workshop will be taking place TOMORROW, Wednesday, August 23^rd at the Yuma Agricultural Center. Come learn about the latest IPM products, practices and trial results from university and industry experts. Registration begins at 7:30 am and the program starts at 8:00 am. Agenda below. Looking forward to seeing everyone there!

 

In the absence of Dacthal (DCPA) growers are looking for different herbicide options for Broccoli and Onions.
The following is data from a broccoli trial done in 2010 by Tickes/Pena, which compares Prowl, Goal Tender, Prefar, Treflan, Devrinol and Dacthal at different application timings. Plots were visually evaluated for weed control of  Goosefoot (Chenopodium murale), Malva (Malva parviflora), and Yellow Sweet Clover (Melilotus oficinalis). The label recommendations for Devrinol are “Use the lower rate on light soil (coarse textured-sandy), and the higher rate on heavy soil (fine textured-clay)”. The rate goes from 1-2 lbs on the DF-XT 50% formulation.
We hope this information is useful in our decision making for broccoli herbicide programs. 

 

Results of pheromone and sticky trap catches can be viewed here.
Area wide Insect Trapping Network   VegIPM Update, Vol. 12, No. 22, Nov 3, 2021.
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts declined considerably over the past 2 weeks across all locations and about average for this time of the season. 
 
Beet armyworm:         
Trap counts decreased in most locations, but well below average for late-October. Most activity in Yuma and Gila Valleys.
 
Cabbage looper:          
Cabbage looper trap counts declined in most areas but increased in the N. Yuma Valley. Activity below normal compared to previous years. 
 
Whitefly:                       
Adults remains active in Dome Valley, Wellton, and Gila Valley, but below average movement for this time of season. 
 
Thrips:                         
Thrips adult movement increased in most locations in the last 2 weeks, particularly in Dome, Wellton, and Tacna. Activity remains below average for late-October.
 
Aphids:                         
Aphid movement increased again sharply in Bard and Yuma and Gila Valleys consistent with N and E winds over the past 2 weeks. Capture about average for this time of year.
 
Leafminers:                 
Adult activity increased sharply in the Gila Valley and Wellton but remains below average for this time of season.
 
Diamondback moth:    
Adults remains active in Dome Valley, Wellton, and Gila Valley, but below average movement for this time of season. Traps located adjacent to cauliflower and broccoli transplants had significantly higher counts, particularly in Dome Valley and Gila Valley.