The fall produce season is off to the races, and so is our diamondback moth (DBM) monitoring project. Although our area-wide trap network is still capturing zero adult DBM moths, AZDA inspectors are already detecting DBM larvae in incoming brassica transplants.

During the first month of inspections in August, AZDA reported 66 shipments of brassica transplants from six California counties. DBM was detected in 28 of those shipments—more than 40%.

These shipments enter Arizona under new phytosanitary requirements intended to reduce the movement of DBM, including inspection and certification within 24 hours of shipment. Understanding what an AZDA detection at arrival means for subsequent DBM risk in the field is therefore an important part of evaluating how well this prevention system is working.

Does a detection at arrival translate into DBM establishment and greater pest pressure after planting—or do some detections pose little subsequent risk?

With funding from the Yuma Center of Excellence for Desert Agriculture (YCEDA) Small Grants Program, we are following inspected transplant lots after planting and linking AZDA inspection findings with subsequent DBM observations and management in commercial fields.

Our goal is to determine which observations made during transplant inspections are useful indicators of subsequent field risk and use that information to develop a practical, risk-based inspection framework for AZDA, growers, and PCAs. Ultimately, better understanding the connection between detections at arrival and what happens in the field can help focus scouting and management where they are most needed—and provide evidence for improving transplant inspection and prevention efforts.

Additional Resources

AZDA Director’s Administrative Order 26-03: Exterior Quarantine for Diamondback Moth

Introduction
Soil, water, and the climate of Arizona and the desert Southwest provide the basic natural resources necessary in the development and management of productive irrigated crop production systems. Understanding the soil resources in each field and the unique characteristics are important factors in maintaining soil health and sustainable crop production systems. Soil surveys have been developed for every county in the United States by the United States Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS). Soil surveys are provided in a consistent format and have been available for many years in hardcopy through local NRCS offices. They can now be accessed online and there are phone apps (i.e., SoilWeb) that are convenient methods of obtaining soil survey information for direct field observations.

Why Soil Surveys Matter in Irrigated Crop Production Systems
Important soil properties such as texture, depth, permeability, salinity, sodicity, and organic matter content are provided for each soil type (soil series) identified in the field. Soil surveys have been conducted and field maps provided on a scale of 1:20,000 in most cases. This provides a high level of detail in identifying soil types and natural field variability.  

In my experiences working with agricultural areas across Arizona and the desert Southwest over the past 40 years, these USDA-NRCS soils are very accurate. They provide an extremely valuable resource for farm and field management. The soil survey maps can be helpful in developing irrigation systems, identifying possible internal soil drainage problems, recognizing water retention capacities of field soils, and evaluating crop variability patterns (Soil Survey Staff, 2017).

Managing Salinity and Soil Drainage
Salt accumulation is a natural consequence of irrigated desert agriculture primarily due to evapotranspiration greatly exceeding rainfall. Without proper leaching and drainage, soluble salts can accumulate, and salinity can limit crop yield and high sodium concentrations can impact soil structure. Soil survey data helps identify areas with shallow restrictive layers that can restrict internal drainage and leaching, natural saline zones, or naturally high sodium levels that require special management (Oster et al., 2012; Franzen et al., 2022).

Digital Tools
The development of the Web Soil Survey and Soil Data Access platforms provides easy access to integrate soil resource information with field implementation. Managing fields for optimal soil health begins with a good understanding of the soil types in each field and the natural variation among soil types across a field (Soil Survey Staff, 2022; USDA–NRCS, 2024).

Arizona soil surveys can be accessed through the following link to USDA-NRCS sites:

https://archive.org/details/usda-arizona?page=2

The Soil Survey of the Yuma-Wellton Area, Parts of Yuma County, Arizona, and Imperial County, California can be accessed through the following link, and pdf copies can be downloaded:

https://archive.org/details/usda-general-soil-map-of-yuma-wellton-area--parts-of-yuma-countyarizona-and-imperial-coun/page/n115/mode/2up

Conclusion
The USDA-NRCS soil surveys are valuable resources for management in irrigated desert agriculture. In the alluvial soils common across the crop production regions of Arizona, there is a high level of natural variability that is often not visible on the surface of the land.  Management practices for optimum soil health and water conservation are optimized by understanding the nature of soil variability in a field and how the soil horizons are arranged in the vertical profile, particularly in the rooting zones of crop plants.

References
Franzen, D.W., D.L. Osmond, and J.J. Meisinger. 2022. Soil fertility and nutrient management in irrigated systems. In: J.L. Hatfield and T.J. Sauer, editors, Soil Management: Building a Stable Base for Agriculture, 3rd ed. ASA, CSSA, and SSSA, Madison, WI. p. 201–230. https://doi.org/10.2136/2018.soilmanagement.c11

Oster, J.D., I. Shainberg, and J. Rhoades. 2012. Salinity and sodicity management. In: R. Lal, editor, Encyclopedia of Soil Science, 2nd ed. CRC Press, Boca Raton, FL. p. 1571–1576.

Soil Survey Staff. 2014. Keys to Soil Taxonomy, 12th ed. USDA–Natural Resources Conservation Service, Washington, DC.

Soil Survey Staff. 2017. Soil Survey Manual, USDA Handbook 18. U.S. Government Publishing Office, Washington, DC.

Soil Survey Staff. 2022. Web Soil Survey. USDA–Natural Resources Conservation Service. Available at: https://websoilsurvey.nrcs.usda.gov

U.S. Department of Agriculture–Natural Resources Conservation Service (USDA–NRCS). 2024. National Soil Information System (NASIS) and Soil Data Access (SDA) User Guide. USDA–NRCS, Washington, DC.

We have recently seen an increase in celery samples coming into the clinic presenting with symptoms including elongated necrotic pitting with significant horizontal cracking on the inner stalks and sometimes total breakdown of the young tissues (petiole and leaf) within the heart. In these same samples, the outer stalks and leaves appear healthy and unaffected.  

At first glance, these symptoms resemble several known issues in celery, including black heart caused by calcium deficiency, black streak caused by boron deficiency, cucumber mosaic virus (CMV), and lygus feeding injury. Field observations have consistently shown low-to-absent lygus populations despite widespread incidence of severely affected celery, making insect damage an unlikely primary cause. CMV can also cause sunken, buff-colored lesions on the stalks but typically presents with additional foliar symptoms including leaf cupping and discoloration. Also, CMV doesn’t discriminate between young and old tissues, and despite testing every sample the YPHC has received thus far we have failed to detect the presence of the virus in any of the samples.  

Furthermore, I have had the chance to walk two severely affected fields in-person, from which I found two consistent observations. First, these symptoms are observed uniformly throughout large sections or the entirety of the field, a distribution pattern which is atypical of a sudden outbreak of a biotic pathogen or insect pest. Second, hosts from different plantings showed uniform severity, which indicates the issue arose at the same time across celery in the area. These two observations suggest that an abiotic culprit rather than a biotic pest is to blame for this sudden eruption of host symptoms.

So with lygus and CMV being unlikely causes and consistently negative cultures for any other bacterial or fungal causes, the last two options that fit the symptoms of these samples are both abiotic in nature. Black heart is a physiological disorder most frequently associated with calcium deficiency. The internal hearts of celery with black heart experience significant breakdown of all tissues due to insufficient calcium transport, similar to what can be observed on tomatoes with blossom end rot. Black streak, similarly, is also a physiological disorder, however, it is most often associated with boron deficiency. Black streak typically presents as elongated, sunken lesions along petioles and stems with significant crosswise cracking along the petioles. However, development of brown areas and die back in black streak cases has also been reported. 

Figure 1. Early blackheart symptoms


Figure 2. Late blackheart symptoms + secondary colonization


Figure 3. Black streak of celery

Both disorders can arise from inadequate fertilization of either calcium or boron or when rapid growth outpaces the plant’s ability to uptake enough of these nutrients from the soil. Both conditions have been linked to several causal environmental factors, but they commonly develop into severe losses when celery is grown in elevated temperatures above 90°F.  

With black streak, greenhouse studies demonstrated that susceptibility was not uniform over time and that the highest susceptibility in celery is observed during the rapid growth phase, about 4-7 weeks after transplanting (Ngouajio 2012). During this period of rapid growth and development boron demand may not be met when the growth of aboveground tissue is further stimulated by hot weather.

When celery is affected by blackheart, it often develops the most severe symptoms as plants approach maturity. This disorder is more frequently associated with rapid fluctuations in soil moisture from drought to flood conditions, excessive fertilization or soil fertility levels of nitrogen and potassium, and high soil salinity.

Of the cases submitted to the YPHC so far, both have been occurring at roughly equal frequencies. 

Sources and further reading:
Ngouajio, M.. “Hot weather requires careful management of celery to avoid black streak disorder”. Michigan State University Extension. 2010. URL: https://www.canr.msu.edu/news/hot_weather_requires_careful_management_of_celery_to_avoid_black_streak_dis

Guan, W.. “Picture of the week: Blackheart of celery”. Purdue University Extension Plant and Pest Diagnostic Lab. 2022. URL: https://ag.purdue.edu/department/btny/ppdl/potw-deptfolder/2022/blackheart-of-celery.html

If you have any concerns regarding the health of your plants/crops please consider submitting samples to the Yuma Plant Health Clinic for diagnostic service or booking a field visit with me:

Christopher Detranaltes, Ph.D. Cooperative Extension – Yuma County Email: cdetranaltes@arizona.edu
Cell: 602-689-7328
6425 W 8th St Yuma, Arizona 85364 – Room 109 

Finger weeders are an in-row weeding tool made from flexible rubber. Pairs are centered on the seed row and overlapped slightly to remove in-row weeds. Our experience has been that finger weeders are effective at removing small weeds (< 3-4 leaf stage), but not large, well anchored weeds. A Texas A&M University colleague shared that they were able to regularly remove 3-4inch tall Palmer Amaranth with finger weeders using a cultivator configuration developed by organic cotton grower Carl Pepper. I was pretty impressed by their video. I think you will be too. Check it out by here or by clicking on the image below.

Acknowledgements
Credit and thanks are extended to Kyle R. Russell, Texas A&M University, for capturing and sharing the video.

Fig. 1. Large Palmer Amaranth being removed from the plant row by finger weeders –
slow motion video. (Video credit: Kyle R. Russel, Texas A&M University. Cultivator
configuration credit: Carl Pepper, Lubbock, TX.)

Cantaloups & Specialty Melons, Late April-Early May

Spring-planted cantaloups and specialty melons are now seeded and established across Yuma. The first 3-5 weeks after planting are the most crucial period for weed management for the entire season. Weed escapes during this window often cannot be corrected once vines begin to run.

Weeds of Concern

• Pigweed (Amaranthus spp., including Palmer)
• Common purslane
• Hairy fleabane
• Spurge species  
• Barnyardgrass & junglerice
• Sprangletop

Most of those weeds are just emerging and are easiest to control now. Once they exceed the 2-4 leaf stage, control becomes inconsistent and costly.

• Melons are poor competitors early
• Canopy closure does not occur soon enough to suppress weeds
• Weeds pressure before vine runs directly reduces:
• o Early vine growth o Fruit set
• o Harvest efficiency

Herbicide – Based IPM Recommendations for Melons
Pre-Plant/Burndown (Before Seeding or Transplants)  

• Glyphosate – annuals and perennials (pre-plant only)
• Paraquat – fast burndown of small weeds (restricted use)
• Carfentrazone (Aim) – small broadleaf weeds

Control all winter weed escapes before seed set, especially mallow and mustards

At or Just After Planting (Pre-emergence):  
Apply at planting or immediately after, then activate with irrigation.  

Broadleaf + Grass Control  

• Bensulide (Prefar) – board activity on grasses and small-seeded broadleaves
• Ethalfluralin (Curbit) – excellent on pigweed and annual grasses
• Trifluralin (Treflan) – grass and pigweed control (incorporation required)

Residual herbicides are essential during the first 3-4 weeks.

Early Post-emergence rescue (Before Vine Run)
Target weeds at the 1-3 leaf stage

Broadleaf  

• Halosulfuron (Sandea) – pigweed, purslane, spurge (size-dependent)

Grasses

• Clethodim (Select, others)
• Sethoxydim (Poast)

Effective on small grasses; timing is critical. Late POST applications after vines run reduce control and increase crop injury risk. 

Things to watch

• Prefar is a better fit when you can use overhead incorporation; it's less effective under drip or furrow irrigation
• Sandea has carryover risk, so plan crop rotation carefully  
• Poast does not control spangletop or annual bluegrass well

Non-Chemical Options Worth Combining
The herbicide list for melons is very limited, but fortunately most melon types grown in the Yuma valley grow rapidly. Non-chemical weed control practices, including cultivation and plastic mulch, can be effective.

Takeaway Message
In Yuma melon production, the most practical program is usually a preplant burndown plus a residual pre-emergence herbicide, then a carefully timed postemergence rescue like Sandea or grass herbicide if needed. The exact choice depends on whether you are growing watermelon, cantaloupe, or honeydew, and whether you use plastic mulch, drip, or furrow irrigation. 

Insect pests are constantly adapting to their environment. Over time, they have evolved ways to overcome control tactics. Repeated use of the same insecticides or tactics places strong selection pressure on pest populations. This allows the few individuals that can survive treatments to reproduce, leading to populations that are increasingly difficult to control, a process known as resistance.

Insects can develop resistance in several ways. Some break down insecticides more efficiently or develop changes at the target site that reduce product effectiveness. Others avoid exposure altogether by changing their feeding habits or movement patterns. In some cases, insects even develop thicker cuticles that reduce or slow down the absorption of insecticides.

Production practices can influence the rate of resistance development. Large, uniform cropping systems and repeated use of the same control tools reduce opportunities for susceptible insects to persist, accelerating resistance.

Figure 1: Chart illustrating how insecticide resistance develops when insecticides with the same mode of action (MoA) are used repeatedly.

What Should You Do to Mitigate Resistance in Insect Pests?
An integrated pest management (IPM) approach remains the best defense against resistance.

Key practices include:

• Using crop varieties that are resistant to pest attack
• Rotating insecticides with different modes of action (MoA)
• Avoiding unnecessary insecticide applications
• Preserving beneficial insects by selecting insecticides with no or minimal adverse effects on them
• Incorporating non-chemical management tools whenever possible
• Maintaining refuges to sustain susceptible pest populations
• Eliminating crop residues after harvest to remove food sources and breeding sites for pests.

No insecticide remains fully effective over the long-term if overused. Reducing selection pressure by avoiding consecutive applications of insecticides from the same IRAC group is critical. The more intensively a single tactic is used, the faster resistance will develop. Resistance can increase production costs, reduce marketable yield, and ultimately affect grower competitiveness. A diversified pest management approach helps preserve the effectiveness of available tools and supports long-term, sustainable pest control.

Additional Reading Materials

1. Calvin W., M. N. Keith, and B. McGrew. 2025. Guidelines for effective management of diamondback moth in brassica crops. University of Arizona Extension Publication. az2143. https://extension.arizona.edu/publication/guidelines-effective-management-diamondback-moth-brassica-crops
2. Ellsworth, P.C., A. Fournier, M. Keith, W. Calvin, A. Brown, W. Dixon, M. King, M. Rahr. 2025. Temporal refuges: a new tool for resistance management [IPM short]. University of Arizona Cooperative Extension, Arizona Pest Management. https://hdl.handle.net/10150/678613

Water conservation is becoming increasingly important for desert growers as reduced snowpack, drought, and climate variability continue to pressure irrigation water supplies. To evaluate whether PolySorb could support irrigation water savings under desert conditions, we conducted a large-field evaluation using reduced irrigation levels with and without PolySorb.

The field study included three irrigation levels: 100% full irrigation treatment (FIT), 75% FIT, and 50% FIT. The 100% FIT treatment was used as the full-irrigation standard. PolySorb was evaluated under the reduced irrigation treatments, 75% FIT and 50% FIT, and was applied at a very low rate, approximately 2 inches below the soil surface (Fig. 1). 

Figure 1. Field application of PolySorb in a desert crop production system at Yuma
Valley Farm Research Center at the University of Arizona.

The full irrigation treatment, 100% FIT without PolySorb, produced 17.5 tons/ac. When irrigation was reduced to 75% FIT without PolySorb, yield declined to 14.7 tons/ac. A stronger yield reduction occurred at 50% FIT without PolySorb, where the yield was 7.8 tons/ac. Adding PolySorb improved yield under reduced irrigation. The 75% FIT + PolySorb treatment produced 16.8 tons/ac, which was very close to the 17.5 tons/ac observed under 100% FIT without PolySorb. This represents only a 0.7 tons/ac difference, or about 4% lower yield, while using 25% less irrigation water. At the 50% irrigation level, 50% FIT + PolySorb produced 12.0 tons/ac, compared with 7.8 tons/ac with 50% FIT alone. This was an increase of 4.2 tons/ac, or about 54% higher yield than the same irrigation level without PolySorb (Fig. 2) 

Figure 2. Fresh yield response to irrigation level and PolySorb application. Yield was
17.5 tons/ac under 100% FIT without PolySorb, 14.7 tons/ac under 75% FIT without
PolySorb, and 7.8 tons/ac under 50% FIT without PolySorb. Adding PolySorb increased
yield under reduced irrigation, producing 16.8 tons/ac at 75% FIT + PolySorb and 12.0
tons/ac at 50% FIT + PolySorb.

These results suggest that PolySorb may help improve irrigation efficiency under desert production conditions, especially at moderate deficit irrigation. The strongest response was observed at 75% FIT + PolySorb, where yield was comparable to full irrigation. PolySorb also improved yield at 50% FIT, although yield remained lower than the 75% FIT without PolySorb treatment.

From a practical grower perspective, PolySorb should not be viewed as a stand-alone solution to water scarcity. However, it may be a useful component of an integrated water-management strategy that includes irrigation scheduling, soil moisture monitoring, crop evapotranspiration information, and efficient irrigation delivery systems. More field testing across crops, soil types, irrigation systems, and seasons is needed, but these results indicate that PolySorb could be a promising approach to help conserve irrigation water in desert agriculture.