Hope you are all enjoying the summer so far and keeping busy. Although, we’re about 2 months away from the Fall produce season, it’s never too early to begin thinking of IPM strategies you will be using to battle key insects next season. This includes keeping track of their typical activity during June, July, and August. Below is a short discussion detailing individual pests. 
 
Aphids:    The major aphid species that are important in produce crops each spring include green peach aphid, foxglove aphid and lettuce aphid.  These species are considered cool season pests and are biologically most active during the winter and spring when temperature average around (55-65 F). We do not find them on summer crops as the high temperatures prohibit their activity. They essentially become extinct each summer only to reappear in the fall to infest crops in Oct-Dec migrating into the desert via N-NW winds that occur after the monsoons.
 
Diamondback Moth (DBM):  Another key pest that disappears each summer but for a different reason than for aphids. The host range of DBM is limited to only brassica crop and plants. Although brassica weeds are common during the winter, they occur during the summer due to high temperatures and dry conditions. Thus, like aphids, DBM populations from the previous spring season become “extinct” during the summer when brassica crops and weeds are absent. They reappear each fall migrating in on high winds associated with tropical storms from Mexico, or arrive into the region on infested brassica transplants from California.
 
Whiteflies:       A resident pest that occurs year-round in the desert. As a warm season pest, whiteflies are most abundant on fall produce crops, and seldom a problem during the winter and spring. Peak abundance occurs during the summer months on cotton, and again in September and October on fall brassica, leafy vegetables and fall melons.  Thus, it is important to control whiteflies in cotton prior to defoliation to prevent large migrations onto fall produce crops. In addition, whiteflies can be found on several weeds such as purslane, goosefoot, ground cherry, and sunflowers. Sanitation in and around fields being prepped for fall plantings is important. Preventatively, growers should consider applying soil, system insecticides such as imidacloprid or Verimark to Fall produce crops.

Beet Armyworm (BAW):  A warm-season pest that occurs year-round in the desert. They tend to reach peak abundance twice a year. Generally, the most important peak is in September and October when weather is ideal for their development, flight activity and oviposition. A second peak occurs in late spring. Activity is generally light during the summer, occurring primarily in alfalfa crops. Although BAW is known to migrate in from the south via monsoon and tropical storms, resident populations annually occur in alfalfa during the summer. Thus, to minimize BAW in fall produce crops, thorough management of BAW can potentially minimize their movement onto Fall produce crops.  Weeds are also a source of BAW (purslane, goosefoot, sunflower and Russian thistle) so sanitation in and around fields is important.
 
Western Flower Thrips (WFT):  Also a resident pest that can be found in the desert year round. WFT is most abundant on lettuce in the late spring, but peaks in abundance on alfalfa, melons and cotton is May and June. During the late summer numbers drop dramatically where thrips can be found on melons and alfalfa and weeds like goosefoot and purslane. WFT slowly move into lettuce again in early fall and are least abundant during the winter.  Sanitation of weeds during the summer can help reduce thrips abundance moving into the fall crops and weeds.
 
For more information see:   Keeping Track of Major Produce Pests During the Summer

The Colorado River Basin is managed in a complex and multi-level legal structure that involves many stakeholders. The Colorado River watershed is divided into the Upper and Lower Basins. The Upper Basin includes the states of Wyoming, Colorado, Utah and New Mexico. The Lower Basin includes Arizona, California and Nevada. A binational treaty governs the releases to Mexico from the Colorado River.

Within the overall structure of the Law of the River, the basin states and the Boulder Canyon Project Act water contractors must work collectively to address their water supply issues. In the Lower Basin, water supplies are administered by a federal water master, designated by the Secretary of the Interior working through the Bureau of Reclamation. In the Upper Basin, the Upper Colorado River Commission serves in the role of administering compliance with the 1922 Colorado River Compact. In addition, every basin also has its own unique set of law governing rights that apply within those states.

The 2007 Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for both Lake Powell and Lake Mead are set to expire in 2026. The seven Colorado River Basin states and stakeholders must work together to develop the new criteria that will replace those guidelines. At present, there is a gridlock in those negotiations between the Upper and Lower Basin states and it must be resolved in 2025 to replace those guidelines expiring in 2026.

As part of the 2025 SW Ag Summit program on Thursday, 20 February on the campus of Arizona Western College, two sessions will be held addressing the future of the Colorado River and management plans for water allocations that will be very important for agriculture in the lower Colorado River Valley in the next decade. This will include a keynote session in the morning and a breakout session will follow. The schedule for these two sessions is listed below.

Keynote Program, 7:30 a.m., 20 February 2025, College Community Center (3C)

The Future of the Colorado River

• Jeff Silvertooth, University of Arizona
• Tom Buschatzke, Director at Arizona Department of Water Resources
• J.B. Hamby, Chairman of the Colorado River Board of California and Colorado River Commissioner

 

Breakout Session – Colorado River Update, 9:30 a.m. MAC 106

Outlook on Basin wide Negotiations for the 2026 Operational Guidelines

• Introduction – Jeff Silvertooth, Moderator, University of Arizona
• Colorado River Perspectives - Principal and Water User Discussion
• Hank Auza, President, Yuma County Water Users Association
• Elston Grubaugh, General Manager, Wellton-Mohawk Irrigation and Drainage District
• J.B. Hamby, Chairman | Colorado River Board of California and Colorado River Commissioner | State of California
• Tom Buschatzke, Director, Arizona Department of Water Resources

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.

Time flies. It’s the first week of February already and that means it is farm equipment/ag trade show season. Upcoming regional events include the WorldAg Expo, Tulare, CA, February 11-13, the Southwest Ag Summit, Yuma, AZ, February 18-20, and AgroBaja, Mexicali, Mexico, March 6-9.  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 or images below.

SourhWest Ag Summit
World Ag Expo
Agro Baja

There are more than 50 broadleaf and grass weeds in this area that are common and have been here for a long time.  It would be great to have an herbicide that will control all of them, be safe to the crop and be gone the next day after harvest.

Obviously, we are a long way from achieving this. What we have done instead is select for the weeds that escape our weed control practices. Anything that shifts the advantage to the crop instead of the weeds will help. Our practices include the use of herbicides, mechanical techniques and hand hoeing. Good weed control can be achieved using all three but may not be economical.

Weed selection due to herbicide availability was evident a few years ago when leaf lettuce was removed from the Kerb label in 2009. It is well known that Kerb, Prefar and Balan were the standard herbicides used in lettuce for the last 60years. Kerb will control the grasses and most of the broadleaves consistently including many that are not controlled by the other two products such as shepherds purse, london rocket and wild mustard. The longer that Kerb was unavailable the more prevalent some weeds would become. On January 12, 2016, the EPA label for Kerb was reinstated for leaf lettuce bringing back the tool to the industry1.

Prefar will control grass consistently, purslane and pigweed most of the time, lambs quarters and goosefoot some of the time. Balan will control grass consistently and many of the small-seeded broadleaves some of the time.

The postemergence grass herbicides were registered about 30 years ago but for broadleaf weeds there has not been a new registration in half a century.

Reference:
1.    Retrieved from the www on Oct 14, 2024 https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=21270#:~:text=On%20January%2012%2C%202016%20the%20Federal%20EPA,55%20day%20prior%20to%20harvest%20(Table%201).

2.    https://cales.arizona.edu/crop/vegetables/advisories/more/weed122.html

As the weather gets cooler, aphids are migrating back to the desert to harm our crops. It is important to revisit some factors that may favor aphid infestations in your crops, specifically lettuce, and take appropriate action against them.  

Nitrogen availability is one of the most important factors in the development of insect pest populations. Excessive application of nitrogen fertilizer to crops will likely increase the feeding preference and consumption rate of insect pests such as aphids, resulting in greater survival, growth, and reproduction. In some situations, high nitrogen levels in plant tissue can decrease resistance and increase susceptibility to aphids’ attacks.

Water management is also very important to consider. Excess water around plant roots can increase nitrogen uptake, which may favor an increase in the aphid population. Thus, supplying proper amounts of nitrogen and water to your crops can tremendously help with aphid management. See this link for more information on this topic.

Lake Mead, the nation’s largest reservoir, continues to decline to historic lows, posing a critical hydrological challenge in the Southwest with significant implications for Arizona agriculture. Prolonged and severe drought across the Colorado River Basin has led to cascading water-use reductions, including a Tier 1 shortage that has cut central Arizona’s agricultural water allocations by 65%.

The drought situation in Arizona has intensified significantly since late 2024 (see Figures 1 & 2 to determine the differences in extreme drought expansion), with extreme drought (D3) conditions spreading across much of the state. Yuma, La Paz, Maricopa, Gila, and now Greenlee counties are fully engulfed in D3 drought, while the expansion has also reached parts of Pima, Mohave, Yavapai, Navajo, Apache, Santa Cruz, Graham, and Cochise counties. This alarming trend signals a severe water deficit, raising serious concerns about its impact on agriculture, water resources, ecosystems, and communities statewide. This crisis underscores the urgent need for innovative strategies to sustain agriculture and secure water resources in the region.

One approach to addressing this crisis is implementing conservative water management, which includes adopting advanced soil moisture monitoring technologies. This raises an important question: How do you select the right soil moisture sensors for irrigation management decisions?

A wide range of soil moisture sensors are commercially available for agricultural use. However, selecting the most suitable sensor for Yuma’s arid environment, where soils are characterized by a pH greater than 8 requires careful consideration of key criteria. The selection process should focus on two critical aspects:

(a) Operational Feasibility:

• Telemetry: Real-time data transmission capabilities for remote monitoring.
• Sensor Cost: Affordability and long-term investment viability.
• Data Logging Cost: Expenses associated with data storage and accessibility.
• Ease of Operation: User-friendliness, installation requirements, and integration with existing systems.

(b) Performance Accuracy:

• Orientation: Proper sensor placement based on soil type, whether horizontal or vertical, to ensure accurate readings.

Calibration: Consideration of factory calibrations versus site-specific calibrations for improved measurement precision.

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.