With fall produce now underway bagrada bugs have begun to show up on direct seeded and transplanted cole crops. Reports of bagrada in local cole crops are beginning to trickle in from PCAs and so far, the pressure does not appear to be as heavy as we’ve seen in the past few years. Populations of bagrada bugs at the Yuma Ag Center however, are as heavy as ever and are quickly causing damage to untreated broccoli plots. Based on research conducted over the past four growing seasons, peak abundance of bagrada bug has occurred from late September to early October. So, what should a PCA expect for this season? Can’t say for sure, but don’t be complacent just because you’re not finding a lot of bagrada adults on your first few fields. It would be wise to assume they will eventually show up in some intensity in some of your acreage, and you should prepare for them accordingly. Monitoring for bagrada at stand establishment should focus on fresh feeding signs on new plant tissue, and adults later in the day when they are most active. Research and anecdotal observations in fields conducted over the past 2 years suggests that direct-seeded and transplanted crops are susceptible to bagrada bug infestations during stand establishment and up to the 6 leaf stage. Furthermore, results suggests that it doesn’t take a large number of bagrada adults to cause significant stand losses or crop injury. In untreated plots, we have consistently observed significant damage (15-20% blind plants) to direct seeded plants during the first 7 days after emergence (cotyledon to 1-leaf Stage) with only finding an average of 1 bagrada adult / 6 row ft. If you readily find fresh feeding signs and/or adults during stand establishment, control should be initiated immediately. This can include chemigation or aerial applications with pyrethroids. Contact insecticides (such as pyrethroids, Lannate, and Lorsban) should be used once stands are lined out and pipe is pulled. After stands are established and plant size increases up to the 2 leaf stage, or on tagged transplants, consider alternating to dinotefuron (Venom/Scorpion) to protect plants from bagrada feeding. This neonicotinoid will also provide knockdown of adult whiteflies and nymphs. More information on bagrada bug management on fall cole crops can be found in these Veg Update briefs: Bagrada Bug Management Tips for the Low Desert and Knockdown and Residual Control of Bagrada Bug With Foliar Insecticides in Broccoli: 2013 Efficacy Report.

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. 

 

Area wide Insect Trapping Network   VegIPM Update, Vol. 11, No. 22, October 28, 2020

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: Moth activity is about average for mid-October, particularly in Dome Valley and south Yuma Valley. 

Beet armyworm: Moths remain active throughout the desert, especially active in Tacna and Dome Valley.

Cabbage looper: Cabbage looper activity remains unusually low for early October, likely a result of unusually hot weather. Larvae are yet to show up in many fields.   

Whitefly: Adult movement has been about average for this time of year. Activity highest in Tacna near fall melons.

Thrips: To date, thrips activity has been seasonably low at all trap locations; activity increased significantly in Roll. 

Aphids: Aphids beginning to show in most traps along the Colorado River (Bard, Gila, Yuma) which is normal for this time of year.  Recent high winds may begin to disperse them throughout the area.

Leafminers: Adult activity below normal for September, but high numbers caught in Wellton in areas where melon harvest has commenced.