As growers begin preparing fields for the spring melon season, PCAs should start considering the threat of seed corn maggots. It’s always best to avoid problems with this pest as you plan ahead for spring planting. Seed corn maggots are always a concern for melon crops planted from Jan-Mar, but may be a more important pest this year because of the potential for cool, wet weather which provides ideal conditions for infestations. Seed corn maggots can cause significant stand reductions in spring melons and other large seeded crops (e.g., cotton, corn, safflower) due to the maggots feeding on germinating seed, roots and stems of young seedlings and transplants. If larvae populations are high in the soil, replanting parts or all of an infested field is often necessary. Not only is this an inconvenience to the grower, but replanting is expensive and can disrupt harvest schedules. Unfortunately, once maggots have been found infesting the soil during stand establishment, there is usually nothing you can do. Thus, avoidance of the problem is the most effective way of preventing stand reductions. First, weather plays a major role in determining the damage potential for seed corn maggot. Melon stands are more susceptible to seed corn maggot during wet, cool spring weather in which seed germination is slowed or delayed. Given the forecast for El Nino conditions this spring, growers should anticipate at least some wet and cool days during stand establishment. These conditions give seed corn maggots a chance to develop in the soil and attack the seeds before they can emerge. But I’ve also observed seed corn maggots take down melon plants under warm dry conditions when fly populations were high. Secondly, our cropping system plays a key role. Melon crops following produce, are the most often attacked because seed corn maggot adults are attracted to freshly tilled fields with high levels of decomposing organic matter and will readily lay eggs in the soil. This includes heavy plant residue remaining after harvest of the previous lettuce or cole crop, as well as applications of composted manure prior to planting. Growers would be encouraged not to plant melons into fields under these conditions. However, if growers decide to plant in these conditions, then it would be wise to use a preventative insecticide applied at planting to minimize the impact from seed corn maggot and give seedlings a fighting chance. A few alternatives are available that have shown activity against seed corn maggot and may be practical for their management in spring melons. For more information, visit Seed Corn Maggot on Spring Melons 2016.

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

The soft-rot bacterium, Erwinia carotovora subsp. carotovora  (syn.= Pectobacterium carotovorum subsp. carotovorum), enters through growth cracks or wounds caused by cold temperatures, insects, other disease organisms, or by mechanical means. Under warm, humid conditions, uninjured tissue may become infected through natural openings.  Prolonged moisture from rain or irrigation and mild temperatures encourage disease development. Insects, tools, rain, clothing, or affected plant tissue can spread the bacteria. The bacteria survive in soil and plant debris.
Symptoms appear as small, water-soaked areas and enlarge rapidly.  Tissue becomes soft and mushy, and within a few days the affected plant part may collapse. An offensive odor usually is present.
Management: 
Cultural: 

• Set out plants in rows to allow good air drainage.
• Cultivate carefully to minimize injuring plants.
• Control frequency and source of irrigation water.Avoid frequent irrigation during head development. Time irrigation to allow the head to dry rapidly. Avoid stagnant water sources.
• Clean and spray storage walls and floors with copper sulfate solution (1 lb/5 gal water). Bactericides such as Clorox, Lysol, and quaternary ammonium products also are effective.
• In storage, use a buffering material such as straw or paper to prevent injury to the heads.
• Keep storage house humidity between 90% and 95% and the temperature between 32°F and 39°F.

Chemical control
·    Cueva at 0.5 to 2 gal/100 gal water on 7- to 10-day intervals. May be applied on the day of harvest. 4-hr reentry. 

• Cease at 3 to 6 quarts in 100 gal water. For greenhouse plants only. Preharvest interval is 0 days. 4-hr reentry. 

 

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.

Corn earworm: CEW moth counts down in most traps over the last week; about average for early October.

Beet armyworm: Trap counts increased in several areas last week, and about average for early October.

Cabbage looper: Cabbage looper trap counts increased in most locations, but still below average for this time of the season.

Diamondback moth: Adult activity spiked 2 weeks ago, particularly in the Yuma and Dome Valleys, but down over the past week. Average for this time of season.

Whitefly: Adult movement increasing Tacna consistent with melon harvests; overall about average for early October.

Thrips: Thrips adult movement peaked 2 weeks ago but down ovr the past week, overall activity above average.

Aphids: Winged aphids beginning to show up the north Yuma and Gila Valleys; below average for October.

Leafminers: Adult activity increased significantly last week in several locations, above average for this time of season.