Now that the weather is finally warming up, PCAs need to be on the lookout for spider mites on melons. Among mite species commonly found in the desert, twospotted spider mites, Tetranychus spp., are the most widespread and economically important. In the desert,  my experience has been that mite outbreaks are more common on watermelons than other netted and mixed melon varieties. However, problems can certainly occur on all melon types. For instance, last spring there were a few situations of mites colonizing cantaloupes in mid-April. Timely control prevented losses to the crops. Under ideal conditions, spider mite populations can increase dramatically, and the hot, dry weather forecast for the next few weeks can be favorable for rapid population growth. For example, mites can develop from egg to adult in about 37 days when temperatures average about 60° F, but at average temperature around 86° F, it only requires 7 or 8 days to complete their lifecycle.   If left unchecked, mite populations are capable of rapidly increasing to damaging levels. Several natural enemies (including predatory mites and thrips, minute pirate bugs and lacewings) play an important role in regulating mite populations below economically damaging levels. Predators can maintain mite populations in check by feeding on slowly developing mite populations. However, when temperatures become hot and dry, the mites can quickly outrun the predator population, particularly following broad spectrum insecticide usage. Whenever possible, it is best to use selective insecticides (e.g., IGRs) when spraying for cabbage loopers and whiteflies to avoid elimination of natural enemies.  Reducing stress on melon plants with good irrigation and fertilization management can enhance plant tolerance to mites.  Well defined economic thresholds have not been established for spider mites in the low desert, so treatment with an acaricide is recommended when significant webbing can be found on leaves and predatory mites and thrips are absent.   Several effective miticides are available for melons including Agri-Mek (and abamectin generics), Oberon, Acramite, Miteus, Zeal and sulfur.  Although spider mites inhabit the undersurface of leaves, most of the new miticides are translaminar and can effectively reach the pests when properly applied to upper leaf surfaces.    If leafminers are present in the field, a product containing abamectin (e.g., Agri-Mek) is a good option. If whitefly nymphs are beginning to build on older leaves, Oberon or Minecto Pro may be an effective option. Also, be aware of honeybees and other pollinators in or around melon fields. If bees are present, be sure to carefully read labels and determine bee safety of a product before making an application in a melon field.  We also recommend that insecticides only be applied at night (e.g. 10:00 pm – 3: 00 am). when honeybees are not actively working in the field. 
 For more information on mites and their management please visit the attached pdf:   Spider Mites on Melons. 

Springtime in the desert serves host to a new spring melon/cantaloupe crop.  That is particularly true in the lower Colorado River valleys.  Cantaloupes (Cucumis melo ‘reticulatus’ L.) or “melons” are one of the important spring and fall vegetable crops of Arizona and the desert Southwest.  
 
Technically, “true” cantaloupes (Cucumis melo ‘cantaloupensis’) are rough, warty fruit, primarily grown in Europe.  On a production scale, cantaloupes are not grown commercially in the United States.  However, in the United States “cantaloupe” has become a general name of all netted, musk-scented melons (Simonne et al., 1998 and Soto, 2012).  
 
Being able to accurately describe and predict important stages of crop growth and development (crop phenology) and harvest dates is important for improving melon crop management (e.g. fertilization, irrigation, harvest scheduling, pest management activities, labor, and machinery management, etc.). Since plants operate on “thermal time”, they have no regard for calendars or time as we commonly measure it.  So, it is best to monitor and predict plant development based on the actual thermal conditions in the plant’s environment.  
 
Various forms of temperature measurements and units commonly referred to as heat units (HU), growing degree units (GDU), or growing degree days (GDD) have been utilized in numerous studies to predict phenological events for many crop plants (Baskerville and Emin, 1969; Brown, 1989; Baker and Reddy, 2001; and Soto, 2012).  A graphical depiction of HU computation using the single sine curve procedure is presented in Figure 1 (Brown, 1989).
 
Since 2000, we have been working on the development and annual testing of a phenology model for desert cantaloupe production for Arizona conditions.  The basic cantaloupe phenology model is shown in Figure 2 (Silvertooth, 2003; Soto et al., 2006; and Soto, 2012).  This melon crop phenology model was developed under fully irrigated conditions.  
 
Guideposts indicated in Figure 2 represent general average or “target” values and a slight degree of variation is normal.  It is important to note that water or nitrogen stress are two factors that will significantly alter physiological development of a crop.  
 
Referencing the data from the Arizona Meteorological Network (AZMET) and several locations in the Yuma area, the HU accumulations (86/55 ºF thresholds) from a range of possible 2024 melon planting dates to 28 April are listed in Table 1.  These HU accumulations can be referenced against the melon phenology model in Figure 2 and crop conditions in the field.
 
I encourage those who are working with spring cantaloupe production this season to test and evaluate this crop phenology model in the field under various planting dates, varieties, and conditions.  The information in Table 1 can help serve as a reference to check melon crop development in the field against this phenological model.  We appreciate your feedback.
 
References:
 
Baker, J.T., and V.R. Reddy. 2001. Temperature effects on phenological development and yield of muskmelon. Annals of Botany. 87:605-613.
 
Baskerville, G.L., and P. Emin.  1969. Rapid estimation of heat accumulation from maximum and minimum temperatures. Ecology 50:514-517.
 
Brown, P. W.  1989.  Heat units. Ariz. Coop. Ext. Bull. 8915. Univ. of Arizona, Tucson, AZ.
 
Silvertooth, J.C. 2003. Nutrient uptake in irrigated cantaloupes. Annual meeting, ASA-CSSA-SSSA, Denver, CO.
 
Simonne, A., E. Simonne, R. Boozer, and J. Pitts. 1998. A matter of taste: Consumer preferences studies identify favorite small melon varieties. Highlights of Agricultural Research. 45(2):7-9.
 
Soto, R. O. 2012. Crop phenology and dry matter accumulation and portioning for irrigated spring cantaloupes in the desert Southwest.  Ph.D. Dissertation, Department of Soil, Water and Environmental Science, University of Arizona.
 
Soto-Ortiz, R., J.C. Silvertooth, and A. Galadima.  2006.  Nutrient uptake patterns in irrigated melons (Cucumis melo L.).  Annual Meetings, ASA-CSSA-SSSA, Indianapolis, IN.
 

Location	15 January	1 February	15 February	1 March
Yuma Valley	994	893	832	680
Yuma N. Gila	972	856	797	650
Yuma South	961	862	802	655

Table 1.  Heat unit accumulations (86/55 ºF thresholds) from four possible 2024 planting dates utilizing Arizona Meteorological Network (AZMET) data for each representative site.
 
Yuma Valley:https://ag.arizona.edu/azmet/02.htm
Yuma South: https://ag.arizona.edu/azmet/36.htm
Yuma North Gila: https://ag.arizona.edu/azmet/14.htm

Figure 1. Graphical depiction of heat unit computation using the single sine
curve procedure. A sine curve is fit through the daily maximum and minimum
temperatures to recreate the daily temperature cycle. The upper and lower
temperature thresholds for growth and development are then superimposed
on the figure. Mathematical integration is then used to measure the area
bounded by the sine cure and the two temperature thresholds (grey area).
(Brown, 1989)


Figure 2. Heat Units Accumulated After Planting (HUAP, 86/55 ^oF)

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.

New automated/robotic ag technologies are coming out all the time. Ever wonder how they function in the “real world” and whether they are cost effective? Western Growers recently released a case study report on the economic impact of Carbon Robotics LaserWeeder on overall weeding costs. The study tracked expenses, productivity, and labor savings of the machine operating over one year on several thousand acres at two commercial farms, Braga Fresh and Triangle Farms. It is a well done, detailed study enriched by insightful comments and practical recommendations made by the farm managers responsible for machine operations. It’s an easy read and well worth the time for those interested in the economic and overall feasibility of laser weeding. Check it out hereby clicking the image below. I don’t want to be a spoiler, but I was surprised to learn that despite the initial high cost of the laser weeder ($1.2 million), overall weeding costs at both farms were reduced by about 40% (>$250/acre) in high-density organic crops such as spring mix and spinach.
Stay tuned. Western Growers plans to release five more automation technology case study reports within the next year. Upcoming reports include grower case studies experiences with automated weeding machines from Stout Industrial Technology, Inc. and Ecorobotix; and with autonomous ag platforms from Burro, GUSS Automation, and Bluewhite.

Fig. 1. Western Growers case study report on the economic impact of Carbon
Robotics laser weeding machine on weeding costs at two commercial leafy
green vegetable farms. Click here or on the figure to view. (Photo credit: The
Western Growers Center for Innovation & Technology)

What can I use to control an infestation of broadleaves in a wheat field that is close to harvesting?  ... our friends PCAs and growers asked.
It is well known that weeds slow harvesting operations and increase combine repair costs; product may have excessive grain moisture and/or weed seeds in wheat³. Some have reported color changes and the taste of weeds in the product.

One commonly used product has been Roundup, and the label recommendations are the following: “This product provides weed control when applied prior to harvest of feed barley and wheat. For feed barley, apply after the hard-dough stage and when the grain contains 20 percent moisture or less. For wheat, apply after the hard-dough stage of grain at 30 percent or less grain moisture” ³.
There are concerns of the presence of glyphosate in shipments from US and Canada which they attribute to “the practice of pre-harvest spraying”. Therefore, some growers are looking for alternatives to this herbicide².
Sharpen (saflufenacil) is a quick acting burndown product for broadleaf weed control in field crops and it has been labeled and approved in the US for this purpose. 
Consulting with a BASF representative we learned that Sharpen is labeled in Arizona (not CA) for this use. The recommended rate is 1-2 fl oz., adding Ammonium Sulfate adjuvant and Methylated Seed Oil. Also, apply at the hard dough stage with no more than 30% moisture, with 10 GPA by ground or 5 GPA by air. 
Knezevic (2009) stated “MSO was the adjuvant that provided the greatest enhancement of saflufenacil across all species tested. COC was the second-best adjuvant and provided control similar to MSO on many weed species. NIS provided the least enhancement of saflufenacil⁴. 
 
An Agronomy Update from Kansas State University recommended to “Consult grain buyer to see if they will accept Sharpen treated wheat because of export restrictions”⁵.

References:

1. http://canola.okstate.edu/cropproduction/herbicides/labels/Roundup%20PowerMax%20Label.pdf

2. https://sustainablepulse.com/2019/08/29/unique-hair-testing-project-reveals-high-levels-of-glyphosate-and-ampa-in-members-of-the-japanese-parliament/

3. https://www.farmprogress.com/weeds/controlling-broadleaf-weeds-in-winter-wheat-is-essential

4. Knezevic, S. Z., Datta, A., Scott, J., & Charvat, L. D. (2009). Adjuvants influenced saflufenacil efficacy on fall-emerging weeds. Weed Technology, 23(3), 340-345.

5. https://cropwatch.unl.edu/2019/ksu-pre-harvest-weed-control-wheat-sharpen-update

Results of pheromone and sticky trap catches can be viewed here.
Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 15, July 24, 2024

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:             
CEW moth counts increased in Roll and Yuma Valley; about average to previous years.
 
Beet armyworm:          
BAW moth counts increase in Tacna and Wellton; comparable to previous summers.
 
Cabbage looper::          
Cabbage looper numbers are low consistent with previous years and higher temperatures.
 
Diamondback moth:      
DBM moths were not caught in any trap; average for this time of the year.
 
Whitefly:                      
Adult movement continues to increase consistent with disking of late melon fields and volunteers.
 
Thrips:                          
Thrips adult activity continues to decline, comparable to mid-summer.
 
Aphids:                        
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity about average for early July.