Temperatures are still warm and worm pressure remains steady in most growing areas.   Here at the Ag Center, beet armyworm pressure is about average for early October, and still troublesome on new stands. Cabbage looper eggs are beginning to now show up. Pheromone trap counts for armyworm and loopers remain below average in most areas. However, diamondback moth larvae are present on broccoli and transplants at the Ag Center.  I’ve had several PCA reports of diamondback pressure in transplanted brassica crops in Wellton and Roll, and in the Yuma Valley. Trap catches have begun to increase also. So far, all insecticide products we’ve tested are providing good Lep control and no complaints from the field.  
 
Fortunately for local PCAs, several insecticide alternatives are available that provide excellent residual activity on Lep pests.   Perhaps equally important, many of the products have unique modes of action (MOA) that can be alternated throughout the growing season. This is important because the most fundamental way to reduce the risk of insecticide resistance is to eliminate exposure of multiple generations of Leps to the same MOA.   By using a different MOA on each subsequent spray application, you can minimize the risk of resistance by Lep larvae to these insecticide compounds. In contrast, repeatedly applying insecticide products with the same MOA for Lep control in the same area will significantly increase the risk of resistance.  This is particularly important with the Diamide group of insecticides (IRAC group 28). These products can be applied as both foliar sprays and soil systemic treatments, and currently 7 Diamide products are labeled for use in leafy vegetables - all with the same MOA (Coragen, Durivo, Besiege, Minecto Pro, Verimark, Exirel and Harvanta).  To avoid confusion among the Diamides, the IRAC group number (28) is placed on each label, adjacent to the product name.  Furthermore, applying a Diamide product (i.e., Coragen/Verimark) to the soil at planting or as a tray drench, and then subsequently applying Diamide foliar sprays (i.e., Harvanta/Besiege) on the same field is not a good idea as it can expose multiple generations of Leps to the same MOA.  For example, under ideal weather conditions, one could potentially expose 5-6 generations of BAW or DBM to the same MOA given the residual efficacy of the diamides.  That’s not a good way to use these products if you want them to remain effective.   Since the Diamides, as well as the other key products currently available (e.g., Radiant, Proclaim, Intrepid, Avaunt, Bts), are critical to effective management of Leps in leafy vegetables, PCAs should consciously avoid the overuse of any of these compounds. The most effective way to delay the onset of resistance by Leps in leafy vegetables is to consider the recommendations provided in the guidelines entitled Insecticide Resistance Management for Beet Armyworm, Cabbage Looper and Diamondback Moth in Desert Produce Crops.

Arizona agriculture utilizes ~ 70% of the water in this state and generates a strong and productive industry. Arizona agriculture generates more than $23B in sales as well as directly and indirectly supporting more than 138,000 Arizona jobs and employing more than 162,000 unique workers. Arizona ranks among leading states in the production of lettuce, spinach, broccoli, cauliflower, cantaloupe, honeydew melons, durum wheat, and other commodities. Arizona is an important area for the seed production of many crops that are used across the U.S. and worldwide.  Many Arizona counties rank in the top 1% of all U.S. counties in terms of crop and livestock production (Murphree, 2018).
 
In response to the Colorado River (CR) water shortage and the current reductions in CR allocations to Arizona via the Central Arizona Project (CAP), which is primarily impacting agricultural irrigation districts in central Arizona, there is an increasing level of scrutiny on agricultural uses of Arizona water.  This of course is accentuated with the recognition that agriculture utilizes ~ 70% of the Arizona water supply. 
 
In the irrigation districts along the mainstem of the CR, there is a common adage of “First in use, first in right.”  This is a fundamental aspect of the “law of the river”, which is an amalgam of the various laws, agreements, and rulings on the governance of CR water.  Therefore, it is important for us to consider and prepare the positive case that can be made for the good stewardship of water resources provided by Arizona agriculture.
 
One common area of criticism that is directed towards Arizona crop production systems, is the use of surface and flood irrigation systems.  The alternative irrigation methods that are commonly advocated for use instead of flood irrigation are methods such as drip irrigation, micro-irrigation systems, sprinklers, etc.  Each of these are good irrigation methods and advantageous under the appropriate conditions.  However, a good case can be made for the very efficient use of flood irrigation systems, particularly with high-flow turnouts and dead level (or very nearly so) basins for irrigation.  When properly managed, these types of flood irrigation systems can be very efficient. 
 
When we know the area to be irrigated, the flow rate of water in the irrigation delivery ditch, and the amount of water needed; then we can determine the proper time or duration for an irrigation event.  If we can get fast and uniform coverage of the field to be irrigated, apply the proper volume of water to replenish the plant-available water supply to the soil, then cut off the flow of irrigation water into the field; we can do a very good job of delivery for high water-use efficiency.
 
To facilitate the process of managing individual irrigations for optimum efficiency, the Irrigator’s Equation can be used to estimate the depth of water applied or time (duration) of an irrigation event.
 
Q x t = d x A
 
Where:            Q = the flow rate, in cubic feet per second (cfs); 
t   = the set time or total time of irrigation (hours); 
d  = the depth of water applied (inches) and 
A = the area irrigated (acres).
 
With an understanding of the dominant soil type in the field being irrigated and the level of soil-water depletion at the time of irrigation, we can estimate the amount or depth of water needed to replenish the soil profile of plant-available water to support the crop and prevent water stress.  
 
In managing crop fields and irrigations, we recognize that soil textures vary in terms of water holding capacities and it is important to understand the dominant soil textures in the field, not only on the surface but also through the depths of the soil profile through the effective rooting depth of the crop, Tables 1 & 2.
 
Collectively, we can manage surface or flood irrigation systems efficiently.  In the crop production arena, it is important to communicate these points effectively.

Table 1. Soil texture and water holding capacity.

 
2. Depths to which the roots of mature crops will deplete the available water supply when grown in a deep permeable, well-drained soil under average conditions.

Source: Chapter 11, "Sprinkler Irrigation," Section 15, Natural Resources Conservation Service National Engineering Handbook
 
 
References:
Murphree, J. 2018. Arizona Agriculture is 23 Billion Dollars Beautiful, Arizona Farm Bureau. 
https://www.azfb.org/Article/Arizona-Agriculture-is-23-Billion-Dollars-Beautiful

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.

Vol. 13, Issue 3, Published 2/9/2022

Over the last couple of years, we have been investigated the use of band-steam to control weeds and soilborne pathogens. The technique has been discussed in previous UA Veg IPM articles (Vol. 12 (5), Vol. 11 (15). Briefly, the concept behind band-steam is to disinfest narrow bands of soil centered on the seedline using high temperature steam prior to planting.
Trials results have been impressive, particularly for in-row weed control (Fig. 1). We’ll be demonstrating our prototype band-steam applicator (Fig. 2) and sharing study results at the 2022 Southwest Ag Summit Field Demo, February 23^rd. More information about the event can be found at: https://yumafreshveg.com/southwest-ag-summit/. I look forward to seeing everyone there.
If you are interested in trying band-steam on your farm, please let me know. We are in the process of constructing a second-generation band-steam applicator that has a higher capacity steam generator and simpler design than our first prototype and are seeking collaborators.
Acknowledgements
This work is partially funded by the Arizona Specialty Crop Block Grant Program.

Fig. 1. Weed control in seedline of beds treated with band-steam (center and left bed) and untreated (right). 


Fig. 2. Band-steaming bed seedlines prior to planting in preparation for the 2022 Southwest Ag Summit Field Demo, February 23^rd (https://yumafreshveg.com/southwest-ag-summit/).

Wellton, AZ


Yuma, AZ

Palafoxia arida is a plant from the family Asteraceae also called the Sunflower family. It is native to the Desert regions of California and the SW United States in AZ, NV, CA, UT, Baja California and Sonora. It is an annual weed that grows erect and has rough hairs on the leaves, which are grayish green and narrow or linear. This plant can grow up to 6 ft has a main tap root. The flower heads are about 2-3 cm long with several (up to 40) tubular five lobed florets white to light pink color. Its habitat includes sandy plains, mesas, washes, dunes. 
 
We found this weed abundantly in our Yuma County Survey. The highest populations were found at the Yuma Mesa around fields. Also found in newly established alfalfa fields. Despite the fact that it prefers sandy soils we also detected Palafoxia all across the Yuma County from the Texas Hill area Wellton, Dome Valley to the San Luis Arizona border.  Please see Yuma County map below. 
The Arizona Vegetable IPM Team will be checking to see if this weed is a possible host for INSV (Inpatiens Necrotic Spot Virus).

Results of pheromone and sticky trap catches can be viewed here.
 
Beet armyworm:               
CEW moth increased the Tacna/Roll area last week, but areawide below average for mid-September.
 
Beet armyworm:         
Trap counts about the same in all locations, below average for mid-September.
 
Cabbage looper:         
Cabbage looper numbers remained low consistent with mid-September.
 
Diamondback moth:   
DBM moths beginning to appear in traps in Tacna/Dome Valley.
 
Whitefly:                     
Adult movement increased in the past week, consistent with cotton defoliation and harvest. Above average for mid-September. 
 
Thrips:                           
Thrips adults increased 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 mid- September.