Whitefly abundance on spring melons is beginning to rapidly build. Furthermore, areawide sticky trap counts indicate that adults are rapidly beginning to disperse, particularly in the Yuma and Dome Valleys. They also appear to be moving ahead of schedule compared to the previous 2 summers (See graph below). Obviously, this has implications immediately for cotton, and eventually for fall /melon produce crops. With spring melon harvest well underway and coming to an end in a couple of weeks, now is a good time to begin thinking about whitefly management in your subsequent crops. The first line of defense in avoiding whitefly issues in fall plantings is effectively controlling whiteflies on cotton this summer. Fortunately, PCAs have several effective insecticides for whitefly management in cotton products (e.g., Knack, Courier). However, it is important that whitefly populations be prevented from building up to large numbers in the spring melons that recently finished or are nearing completion of harvest. With whitefly movement beginning to rapidly increase, we anticipate population growth will increase significantly over the next 2 weeks with the forecasted high temperatures and area-wide melon harvests. Growers and PCAs should not hesitate to knock these populations down on pre-harvest melons. Under current weather conditions (hot and dry), immature populations can rapidly build-up and cause honeydew/sooty cold contamination on fruit. Furthermore, the longer a harvested melon field remains untouched, the more whiteflies that can potentially be produced. Once harvest is complete, proper sanitation in spring melons is critical for preventing unnecessary whitefly dispersal into cotton. It is highly recommended that melon growers quickly destroy plant residue as soon as possible following harvest. A delay in disking under melon fields following harvest can provide a large source of adult whiteflies that will readily move into nearby cotton. These fields also potentially extend the host-acquisition period for CYSDV. A quick survey last week showed that overall CYSDV incidence is light in spring melons, but almost all fields had some virus on field edges. The longer the fields remain after harvest, the more virus that can potentially spread. Once melons have been disked and flat-watered, it is common for volunteer melons to germinate and emerge during July and August. The rapid destruction of these volunteer melons between spring and fall crops can reduce the source of whiteflies and virus inoculum available. This can be done by disking or applying a contact, burn-down herbicide to fields. Volunteer melons should be destroyed as soon as practical. Our research has indicated that fall melons planted within 2 miles of last spring’s melons and/or volunteers are at a high risk of CYSDV infection. Ideally, it is in the Ag communities best interest to use sound cultural management practices, such as sanitation, to eliminate and avoid unnecessary sources of whiteflies before the fall produce and melon seasons begin. For more information on cultural management practices for whiteflies click on this link:  Cultural Practices for Whitefly Management in Desert Melons.

Improvements of irrigation and crop water management are always central to any discussions in the agricultural communities of the desert Southwest regarding higher crop production efficiencies.  That is particularly true in these days of water shortages.
In any crop production setting the crop (plant)-soil-water relationships are essential to producing a healthy and productive crop.  In desert agriculture, water is our first limiting agronomic (crop and soil) factor and there is no substitute for that.
Amid all the discussions about improvements in irrigation efficiency, the focus on plant-soil-water relations needs to be continually emphasized.  The objective of any irrigation system is to provide adequate irrigation water to the soil for the benefit of the crop.  Thus, it is important to understand the soil conditions and the actual crop-water needs for each irrigation event.

Every combination of a soil and a specific crop is unique, and that delicate relationship is compounded by the above ground environment the plant is growing in, the meteorological conditions.  The dynamics of crop-water demand change with each plant species and it will vary daily within a given crop in response to soil conditions, stage of growth, and meteorological conditions, i.e., temperature, humidity, wind speed, solar radiation, etc.   These meteorological factors must be appropriately considered for efficient irrigation management, irrespective of any type of irrigation system, i.e., flood, sprinkler, drip, etc.
In Arizona we are fortunate to have the Arizona Meteorological Network (AZMET) in place and fully operational with high quality data being collected from agricultural areas across the state on an hourly basis.  At present, this data is summarized daily from 25 agricultural sites and seven urban sites across the state.  https://ag.arizona.edu/azmet/

Dr. Paul Brown, Extension Specialist in Biometeorology (retired) began the development of the AZMET system in 1985 and the full operation of the system began in January 1986.  Prior to his retirement a few years ago, Dr. Brown managed and directed the AZMET system along with a robust research and Extension education program to provide numerous crop production tools that this system supports.  Together, Paul Brown and Bruce Russell developed an excellent weather system that is available to us all.   Dr. Jeremy Weiss now directs the AZMET program.

The meteorological data collected by AZMET include temperature (air and soil), humidity, solar radiation, wind (speed and direction), and precipitation.  AZMET also provides a variety of computed variables, including heat units (degree-days), chill hours, dew point, and reference crop evapotranspiration (ETo).  AZMET data are summarized in a variety of formats, including several ready-to-use summaries and comma-delimited (raw) ASCII text files that can be imported into most database and spreadsheet programs (Russell, 2011).
I have participated in numerous discussions recently regarding efforts to manage water resources in a broad sense, such as within an area or district, as well as in individual crop fields where the use of satellite-based evaporation (ET) estimates are being considered for application.  In Arizona, that should not be necessary since we have AZMET stations on the ground that are well-placed in agricultural areas with high quality data available daily.  The AZMET system provides direct measurements of daily atmospheric conditions that our crops are dealing with in each of the 25 locations.

With AZMET and the information directly available and accessible, in my view we should be using this system for our weather-based needs for crop management and not a remote satellite system.  Even if someone insists on using satellite-based systems, it will need ground truthing and AZMET data would be essential for that.
We should be using the AZMET data and related crop management tools.  This system has been developed by the University of Arizona Cooperative Extension System and it is openly available for direct access and use.

References:
Russell, B. 2011.  AZMET.  The Arizona Meteorological Network : A Brief Overview.  University of Arizona Cooperative Extension.  https://ag.arizona.edu/azmet/azmet04.htm

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.

At the 2024 Southwest Ag Summit Field Demo a couple of weeks ago, many of the latest technologies were demonstrated in the field. Most were related to pest control. Several of the technologies demonstrated or on display at the event are brand new to the Yuma, AZ area. The new technologies presented included an implement designed for cultivating high density crops (Fig. 1a), a field scale drone sprayer (10.6 gal) (Fig. 1b), a high precision spot sprayer (Fig. 1c) and a self-propelled machine that disinfests soil prior to planting using steam. Updated versions of laser weeders, camera-guided cultivators and smart, automated in-row weeding machines (mechanical) were also demonstrated. Over the next several years, it will be interesting to watch the technologies in this space evolve further and become integrated into our cropping systems.

Fig. 1. New pest control technologies demonstrated/on display at the 2024
Southwest Ag Summit Field Demo included a) Oliver¹ high density cultivator b)
DJI Agrospray T40 drone sprayer c) Ecorobotix ARA high precision spot sprayer
and d) UC Davis/University of Arizona self-propelled steam applicator for
disinfesting soil prior to planting.

[1] Reference to a product or company is for specific information only and does not endorse or recommend that product or company to the exclusion of others that may be suitable.

The Southwest Agricultural Summit that recently took place in Yuma included a breakout session on Thursday, 21 February 2024 titled “New Developments in Weed Control”.
In this session Jose Antonio Cabrera representing BASF technical services for Coastal CA and Arizona provided a review of the new technologies being developed by his company in the Weed Control area. This includes new active ingredients as well as novel encapsulation technologies. The breakout session also included the lecture “Registration Support for Pest Management Tools in Specialty Crops, The IR-4 Project: Purpose and Process” by Roger B. Batts. “The IR-4 Project was established in 1963 by the U.S. Department of Agriculture to ensure that specialty crop farmers have legal access to safe and effective crop protection products. Helps growers address pest management concerns, develops data necessary for the registration of safe and effective pest management solutions with the U.S. Environmental Protection Agency¹.
Roger is the Weed Science biologist from the NC State University IR-4 headquarters. If you have questions such as: What is the IR-4 Mission? Why is IR-4 Needed? What are the programs within the IR-4 project? you will find some answers in the IR-4 Presentation Slides here.
We are currently conducting trials in Yuma in coordination with this project that could result in the addition of new labels and weed control tools for our Arizona vegetable growers.
Thank you for attending the SW Ag Summit Weed Science breakout session.
 
 
Reference:

1. https://www.ir4project.org/

 

Get your free copy of the Weed Seedling Identification Pocket Guide at the Yuma
Agricultural Center.

 

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth light in the past 2 weeks, below average for the beginning of the produce season.
 
Beet armyworm:          
Trap counts increasing in all locations, about average for early September.
 
Cabbage looper:           
Cabbage looper numbers remained low consistent with early September.
 
Diamondback moth:      
DBM moths not active in any trap since June; expected this time of the year.
 
Whitefly:                       
Adult movement increased in the past week, above average for early September. 
 
Thrips:                           
Thrips adults light in most locations, and trending above average to previous years.
 
Aphids:                         
Aphid movement is absent and consistent with what we typically see during the summer and September. 
 
Leafminers:                   
Adult activity tending downward in most locations, below average for early September.