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.

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.

Options for delivering pesticides in melons post emergence are generally limited to spraying due to their viney growth habit. Injecting soil applied pesticides sufficiently close to the root zone for effective uptake with knife injectors in not possible without clogging equipment or causing crop injury. Several years ago, we investigated the use of an alternative device for delivering liquid chemicals post emergence called a point injection system. Point injection systems were developed in the late 1980’s as a method for applying ag chemicals post emergence with minimal root damage and soil disturbance.  These systems utilize hollow, pointed tips attached to a rotatable wheel to inject liquid products into the root zone at precise intervals and depths (Fig. 1).  Point injection technology has been used primarily as a fertilizer applicator in wheat and corn, however the system also has potential to improve the efficacy and usefulness of soil applied pesticides since it can be used to apply product to mature plants without damaging plant roots or causing crop injury.

In the fall of 2014, in cooperation with Mark White, Bayer CropScience, we tested a point injection system with Sivanto in cantaloupe. Traditionally, the product is soil applied at planting. The objective of the project was to determine if the technology can be used to apply Sivanto after plants have emerged to extend the window when the pesticide can be soil applied. Treatments included applications of 1) Sivanto at planting, 2) Scorpion 35SL at planting, 3) Sivanto post-emergence, 4) Scorpion 35SL post-emergence and 5) a combination of Scorpion 35SL at planting plus Sivanto post-emergence (Table 1). The target pest in these trials was whitefly. Results of the trials in Table 1 showed that use of point injection significantly reduced adult whitefly populations by about 2/3rds 6 (DAT) (45 DAP) as compared to other treatments. At the end of the trial, 24 DAT (63 DAP) cucurbit yellow stunting disorder virus (CYSDV) was about 25% lower. This was a 1-year trial and so conclusions should be considered preliminary, but the results do show good promise for late season soil application of Sivanto.

Over the years, we have conducted trials with point injection systems applying fungicides in cotton (Siemens, 2016, unpublished data) and fertilizers in broccoli, iceberg lettuce and romaine lettuce with improved pesticide efficacy, nutrient use efficiency and higher crop yields as compared to conventional application methods (Siemens and Gayler, 2016). Point injection systems are commercially available from several manufacturers. The Ag Mechanization Extension Program at the Yuma Ag Center has a commercial 4-row unit that is available for field demos. If anyone is interested, please contact me.

References
Siemens, M.C. & Gayler. R.R. (2016). Alternative systems for cultivating and side dressing specialty crops for improved nitrogen use efficiency. ASABE paper No. 162456725, pp. 9. St. Joseph, Mich.: ASABE.

You can link article to here - https://arizona.pure.elsevier.com/en/publications/alternative-systems-for-cultivating-and-side-dressing-specialty-c

The off-target movement of Dicamba and 2,4-D that was applied to resistant cotton and soybeans in the Midwest and south has been in the news for the last few years. It has exploded recently with the cancellation of these uses by a Federal court and the EPA. There have

not been serious problems with these herbicides here in Arizona. The focus of this article is to explain why not.

The Problem
Much of the cotton, corn and soybeans grown in the U.S. was Glyphosate resistant for several years. The number of Glyphosate resistant weeds have increased every year and new concerns about the effect of Glyphosate on human health and environmental safety have arisen. In response to this problem, new varieties of cotton, corn and soybeans have been developed that are resistant to a couple of old but highly effective herbicides, Dicamba and 2,4-D. These herbicides have high vapor pressures and can volatilize after application. They change from a liquid or solid to a gas after application and can move, sometimes long distances, in the air. Any herbicide can drift onto sensitive crops during application and cause injury. This is different than volatilization. New formulations of 2,4-D and Dicamba have been developed, however, that have significantly lower volatility. Studies have shown that while the potential is lower that it still can occur.  Volatilization of both Dicamba and 2,4-D have caused widespread problems to field crops, trees, parks, school yards, landscapes… to cause “Silent Spring “type conditions in the Midwest and south.  Volatility problems occasionally occur but widespread and serious problems have not been encountered in Arizona.

Environmental Conditions
The extreme conditions that exist during the summer in the low deserts of Arizona all contribute to herbicide volatility. High temperature, low humidity and the occurrence of temperature inversions have always made it difficult to use volatile herbicides here. Growers and Pest Control Advisers have learned to be cautious when using these products. They are rarely used after daytime temperatures go much above 90 degrees.

Acreage and Crop Diversity
Crops are grown in Arizona on a smaller scale and more intensively than they are in the Midwest and south. This is especially true in the southwestern counties. The acreage of cotton in 2019, for instance, was 173,000 acres in Arizona,4,350,000 in Texas,1,305,000 in Georgia,550,000 in Oklahoma and 497,000 in Alabama. This smaller scale allows Arizona growers to practice more careful management. Sprayers are cleaned more carefully or dedicated to spraying only volatile products. Fields and surrounding area are checked more frequently. In high acreage states, tens of thousands of acres can be treated at the same time with the same products. The amount of herbicide in the environment at those times is very high.  In Arizona not only are crops grown on a smaller scale, but they are more diversified. It is not uncommon to see 3 ,4 or more different crops being grown at the same time on a 20 acre block. When fields are sprayed it is done very carefully.

Newer formulations and Varieties
New formulations of both Dicamba and 2,4-D have been developed that are much less volatile than the old formulations. Although some of these are promoted as non-volatile, they can still move. Some studies have shown that they are 30 to 50% more stable. It will be variable and dependent on many factors. It is important to choose those cotton varieties that have been developed to tolerate Dicamba or 2,4-D. According to Randy Norton, U of Az. Cotton Specialist, upwards of 60% of the cotton varieties being grown in Arizona this year are Dicamba resistant. Randy states that these varieties were selected for their yield and lint quality more so than their resistance to Dicamba.

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts decreased considerably y in the past 2 weeks and about average for late summer
 
Beet armyworm:         
Trap counts stay active in some locations (Yuma Dome Valley and Wellton) particularly near alfalfa
 
Cabbage looper:         
Cabbage looper numbers remain low consistent previous years.
 
Diamondback moth:      
DBM moths were not caught in any trap since June; average for this time of the year.
 
Whitefly:                      
Adult movement decreased in past 2 weeks consistent with previous years
 
Thrips:                         
Thrips adults decreasing in most locations, and trending comparable to previous years.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity has highest in Wellton and Dome Valley, and slightly above average for early August