As the spring melon harvest begins to wind down it is important to start thinking about whitefly management in fall produce and melons crops. The first line of defense in avoiding whitefly issues in the fall vegetable plantings is for PCAs and growers to be vigilant in their whitefly management program on cotton. In the Yuma area, cotton is the primary host crop for whiteflies during the summer, although alfalfa and sudangrass may serve as alternate hosts in some areas. However, before whitefly management begins in cotton, it is important that whitefly populations be prevented from building up to large numbers in the spring melons that recently finished harvest, or that will be done in the next week or so. In surveying melon crops for CYSDV this spring, it became readily apparent that a large proportion of the spring melon acreage throughout the area was grown near cotton. In fact, our surveys show that on an area-wide basis almost 75% of the melon acreage this spring were grown either adjacent to, or within a 1/2 mile of, cotton. Although whitefly numbers have been relatively light thus far, increased whitefly numbers have been observed over the past week in cotton coinciding with higher temperatures and area-wide melon harvests. Thus, proper sanitation in spring melons is critical for preventing unnecessary whitefly buildups in 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 can readily disperse into cotton, especially when they don't need to fly very far. These whiteflies may also move into nearby weeds many of which (e.g., common mallow and silverleaf nightshade) are hosts for the Cucurbit Yellows Stunting Disorder Virus (CYSDV). Another source of whiteflies and CYSDV during July and August can be volunteer melons in fields where spring melons had previously been grown. These plants also potentially extend the host acquisition/transmission period for CYSDV. This may be important too since CYSDV incidence in spring melons (albeit at non-economic levels) was quite evident this year. Our experiences to date suggest that the incidence of CYSDV in fall melons is generally much higher in fall plantings growing in proximity to where melons were produced the previous spring. For more information on sanitation practices see Whitefly Management on Desert Vegetable and Melons.

Soils with excess soluble salts, saline soils, and/or excess sodium (Na⁺) concentrations (sodic) are a natural feature of desert soils and common in arid land agriculture.  This is primarily due to an accumulation of soluble salts near the soil surface as water evaporates from the soil surface.
 
Saline soils are a problem in crop production systems because of the sensitivity to salinity of crop plants, although plants vary in their degree of sensitivity.  The period of greatest plant sensitivity to salinity is in the early stages of development, during germination and stand establishment.
 
Sodic soils are a problem in crop production systems because of the adverse effects of excess sodium on soil structure, causing a dispersion of soil particles and the breakdown of soil aggregates.  This leads to poor water infiltration and percolation in the soil profile.
 
Some basic points associated with saline and/or sodic soils and management are outlined in the following sections.
 

1. Saline soils have an electrical conductivity of the soil solution (extract, EC_e) of EC_c > 4 dS/m.  Functionally, saline soils have sufficient soluble salts to interfere with and diminish plant growth and development.
   1. Soil salinity is a relative term or condition based on the critical salt sensitivity levels of the crop plant in question.
   2. Plants vary tremendously in their degree of salt tolerance.
   3. Reclamation and management of soil salinity requires an understanding of the specific level of sensitivity of the target plant to salinity.
   4. Saline soils commonly have good soil aggregation and structure.
   5. Reclamation of saline soils requires sufficient water to accomplish leaching and the removal of soluble salts.  Thus, good internal soil drainage is important.

 

1. Sodic soils have a high level of exchangeable sodium (Na⁺) on the soil cation exchange complex (CEC).  Sodic soils have an Exchangeable Sodium Percentage, ESP > 15 of the soil CEC or a sodium adsorption ratio, SAR > 13 from the soil extract.
   1. Sodic soils commonly have poor soil structure and aggregation due to the dispersed condition of soil particles caused by high concentrations of Na on the CEC.
   2. In practice, finer textured soils, e.g. clay, clay loam, silty clay loam, etc. with high clay content can develop sufficient dispersion and poor soil structure at ESP or SAR levels ~ 6-10.  So, the ESP and SAR designations are general and not absolute.

https://www.nrcs.usda.gov/wps/PA_NRCSConsumption/download/?cid=nrcseprd589210&ext=pdf
Sodic soil reclamation does require an amendment that will facilitate the chemical exchange of Na⁺, usually from a calcium (Ca²⁺) source, such as gypsum (CaSO₄).
 

1. Reclamation for saline soils requires additional irrigation water for leaching.  Chemical amendments are not necessary for soluble salt removal.

An effective and straightforward method of calculating a leaching requirement (LR) can be calculated with the following equation that was presented by the USDA Salinity Laboratory (Ayers and Westcot, 1989).
Leaching Requirement (LR) Calculation:

Where: 
ECw = salinity of the irrigation water, electrical conductivity (dS/m)
ECe = critical plant salinity tolerance, electrical conductivity (dS/m)

1. Saline soils do NOT need amendments for reclamation or management.  Only leaching is needed.

 

1. Sodic soil reclamation involves a two-step process:

1. Exchange of Na with Ca and 2) leaching of soluble Na⁺ from the crop root zone.

 

1. Adequate soil leaching is required in both cases of saline and sodic soils.
   1. In the case of sodic soil reclamation, the leaching needs to occur after appropriate amendment applications for Na⁺ exchange with a suitable cation such as Ca²⁺.

 

1. Adequate drainage is necessary to accomplish sufficient leaching of solutes through the soil profile and below the root zone in the reclamation of both saline and sodic soils.

 

1. Irrigation systems capable of delivering sufficient water for leaching are necessary.
   1. Level basin flood irrigation best serves salinity leaching requirements.
   2. Sufficient salinity leaching can be accomplished with furrow flood or overhead sprinkler irrigation.
   3. Drip irrigation systems much be designed to provide sufficient volumes of water to accomplish adequate soil leaching.

i.Drip irrigation systems are commonly very limited in this respect.
 

1. Crop rotation systems are important in leaching and salinity management.
   1. For example: Crops planted on the flat and irrigated by level basin irrigation serve to facilitate good salinity leaching in a field.

i.Examples: wheat, alfalfa, sudangrass, etc.
 

1. Good field observations of crop growth and development in conjunction with regular soil and water sample analysis are key elements to the management of salinity and sodicity in agricultural fields.  

For example, young plants in the germination and seedling stages of development are most susceptible to salinity and water stress.  Abnormal amounts of seedling damage and/or difficulties in germination can often be early signs of increasing soil salinity.
Also, early signs of increasing salinity are often observed with plants demonstrating water stress with plant-available water levels in the soil that should seemingly be adequate for maintaining non-stressed plants.  Thus, fields that are requiring an irrigation in shorter intervals than usual can possibly be an early sign of increasing salinity and it is good to follow-up with a good set of soil samples and a sample of the irrigation water to check.
Early identification of problems in the field with increasing Na concentrations are commonly noticed with increasing tendencies of the soils in the field to form surface crusts very easily, which reduces water infiltration into the soil surface.  This is often recognized at the time planting and stand establishment with germination problems resulting from increasing degrees of soil crusting.

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%). Spinach ‘Revere’ was seeded, then sprinkler-irrigated to germinate seed Jan 18, 2024 on beds with 84 in. between bed centers and containing 30 lines of seed per bed.  All irrigation water was supplied by sprinkler irrigation.  Treatments were replicated four times in a randomized complete block design.  Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed.  Treatments were applied with a CO₂backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles. 
 

Month	Max	Min	Average	Rainfall
January	68	42	54	1.14 in
February	73	47	59	0.50 in
March	77	50	63	0.31 in

 
Downy mildew (caused by Peronospora farinosa f. sp. spinaciae) was first observed in plots on Feb 19  and final reading was taken on February 26, 2024. Spray date for each treatments are listed in excel file with the results.   Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft² areas within each of the four replicate plots per treatment.  The number of spinach leaves in a 1-ft² area of bed was approximately 144. 

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that  provided effective control against the disease include Orondis ultra, Thrive 4 M, Fungout, Cevya, Eject and Zampro. No phytotoxicity was observed in any of the treatments in this trial.

Earlier this year, we completed fabrication of a prototype commercial scale steam applicator for injecting steam into the soil prior to planting. The concept behind soil steaming is similar to soil solarization - heat the soil to levels sufficient to kill soilborne pathogens and weed seeds (typically 140 °F for >20 minutes). The self-propelled machine is principally comprised of a 100 BHP steam generator mounted on tracks and a steam applicator sled (Fig. 1). Steam is applied via shank injection as the machine travels through the field. After cooling (< ½ a day), the crop is planted into the disinfested soil.

The device has been demonstrated in several on-farm, field-scale (>1-acre plots) tests in Salinas, CA this summer. Although the trials are still in progress, preliminary results indicate that the machine is performing well and similar to our previous steam applicator prototypes. In those trials, we found that soil steaming provided excellent weed control (>90%), suppressed problematic soilborne diseases (Fusarium wilt of lettuce >50%, lettuce drop >70%), reduced Pythium spp. counts in soil assays (>93%) and increased crop yields (>24%).

For this upcoming season, we are seeking collaborators to conduct similar field-scale on-farm demonstrations in Yuma, AZ. The primary objectives would be to assess the viability of soil steaming at the field-scale level and obtain grower feedback on the device’s commercial potential. The machine can be adjusted to work with most bed configurations including narrow (40”, 42”) and wide (80”, 84”) beds, and is suitable for use in conventional or organic crops (soil steaming is organically compliant). To date, the device has been successfully tested in iceberg lettuce, romaine lettuce, baby leaf spinach and carrot crops.
If you are interested in an on-farm demo of soil steaming, please let me know. We have resources to conduct 3-4 on-farm demos, so space is limited. I’d be happy to work with you.

Fig. 1. Self-propelled steam applicator principally comprising a a) 100 BHP steam
generator mounted on tracks and a b) steam applicator sled that applies steam via
c) shank injection as beds are formed.

We are planning some Broccoli herbicide trials at the Yuma Agricultural Center. The idea is to have some demonstration plots for you to come and visit.  Will evaluate new and old products with different rates and incorporation methods hoping to obtain additional data on phytotoxicity and weed control. The goal is to have the demo plots available to PCAs and growers at the Yuma Agricultural Center as well as document the observations and make them available to all people in the industry.
Do you have an idea of a treatment or combination that could possibly perform great for our weed complex? If you like to participate creating this protocol please send us your ideas and suggestions. As an example we could play with older products such as Treflan, Prefar, Prowl, Devrinol, Goal Tender, Clethodim etc. Some suggest different levels of sprinkler incorporation (8, 12, 24, 36 hours) for Devrinol. Others apply Treflan to flat ground then disk and put beds, come back with Goal, or Clethodim.
 If you like to include a treatment please send it to marcop@ag.arizona.edu

Researchers at the University of Wisconsin-Madison have developed a device called “Insect Eavesdropper” that allows real-time detection of insect pests attacking crops. The Insect Eavesdropper is equipped with highly sensitive contact microphones which allow it to capture the sounds of insects eating and moving inside plants. The researchers claimed that by eavesdropping on the sounds within the plants, one can gain insights into insect presence, insect density, insect interaction with the crops, insect feeding behaviors, etc. The device works by clipping a sensor onto plants in the field while the data is monitored remotely to determine when pests are active and where they are concentrated. According to the inventors, by using advanced algorithms, the device can accurately identify the type of pest present, even before visual signs of infestation become apparent. 

If this device works as described, it would be a very useful tool for pest monitoring. I you would like to read more about the Insect Eavesdropper technology click on this link.

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth increased the Dome Valley area last week, but areawide below average for early October.
 
Beet armyworm:         
Trap counts highest in Tacan, Wellton and Dome, but below average for early fall.
 
Cabbage looper:          
Cabbage looper numbers remained low consistent with late-September.
 
Diamondback moth:   
DBM moths beginning to appear in traps in Wellton/Dome Valley, trending on average for early fall..
 
Whitefly:                      
Adult movement down in the past week, above average for late-September. 
 
Thrips:                         
Thrips adult activity beginning to increase, and trending about average to previous years.
 
Aphids:                        
First winged adults captured for the season, consistent with heavy winds from W-NW last week. Can anticipate aphid flights to increase in the coming weeks.
 
Leafminers:                   
Adult activity tending downward in most locations, average for late-September.