With the produce season essentially finished, it’s time to begin thinking about insect management in melons. Spring melon crops are rapidly growing, and so are insect pest populations. Cabbage loopers and leafminers are becoming evident in some areas, and PCAs should start ramping up their monitoring and sampling. More importantly, whitely populations are quietly becoming abundant on the spring melons of all sizes. Adults can easily be found on recently planted melons located at the Yuma Ag Center, and reports from local PCAs suggest that adult populations are beginning to show up on older plantings. As temperatures increase and crops/weeds mature, avoidance of excessive feeding from whitefly nymphs should be the primary concern on all melon types. Although CYSDV does occur in later spring melons, it is rarely yield limiting. But honeydew and sooty mold contamination on cantaloupes, mixed melons and watermelons can significantly reduce quality and marketability is whiteflies are not adequately controlled.  Our research has shown that to prevent fruit yield and quality losses on spring melons, a foliar insecticide treatment should be applied on threshold; that is, when average adult numbers exceed 2 per leaf when averaged across an entire melon field. At this level of adult abundance, immature populations are beginning to colonize. Timing sprays based on the adult threshold has been shown to significantly reduce the chance of yield / quality losses during spring harvests.  This threshold applies for the use of recommended IGRs (Courier, Knack, Cormoran, and Oberon), foliar applied neonicotinoids (Assail, Venom, Scorpion), neonicotinoid-like compounds (Sivanto prime and Transform), diamides, (Exirel and Minecto Pro) and the feeding disruptors (PQZ and Sefina).  For more information on whitefly management and available insecticides, go to these documents on Insect Management on Spring Melons: Whiteflies and Whitefly Control Chart-Spring Melons -2024. Also, be aware of honey bees 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.  If applications are necessary during bloom, only apply a product that is considered bee safe (e.g., PQZ, Sefina, Sivanto, Assail). We also recommend that insecticides only be applied when honeybees are not actively working in the field (e.g. 10:00 pm – 3: 00 am).

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%). Lettuce was seeded, then sprinkler-irrigated to germinate seed on Nov 28, 2023 on double rows 12 in. apart on beds with 42 in. 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, which contained two 25 ft rows of lettuce. Plants were thinned Jan 17, 2024  at the 3-4 leaf stage to a 12-inch spacing. 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.

Month	Max Temp (°F)	Min Temp (°F)	Average Temp (°F)	Rainfall
November	80	51	65	0.08 in
December	71	44	57	0.82 in
January	68	42	54	1.14 in
February	73	47	59	0.50 in

 
Powdery mildew (caused by Golovinomyces cichoracearum) efficacy trial treatments were made on February 15,2024, February 23, 2024, March 4, 2024, and March 12, 2024and .Disease was first seen on February  26,2024. Disease rating was done on March 15, 2024.   Disease severity was determined  by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 0.5 = one to a few very small powdery mildew colonies on bottom leaves; 1 = powdery mildew present on bottom leaves of plant; 2 = powdery mildew present on bottom leaves and lower wrapper leaves; 3 = powdery mildew present on bottom leaves and all wrapper leaves; 4 = powdery mildew present on bottom leaves, wrapper leaves, and cap leaf; 5 = powdery mildew present on entire plant. These ratings were transformed to percentage of leaves infected values before being statistically analyzed. Yield loss due to rejected lettuce heads would likely begin to occur on plants with a powdery mildew rating above 2.0 (percentage of leaves infected value of 40).         
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. The most effective fungicides were Rhyme, Merivon, Quintec, Cevya, Luna Sensation, Luna Experience, and Elisys. 

We continually select for those weed species that thrive under our production practices and escape current control techniques. Shepardspurse is one of several weed species that have been around for a long time but that growers and pest control advisors have seen become increasingly widespread in recent years.

The botanical name for shepardspurse is Capsella bursa and it is in the mustard or crucifer family. This is a large family of plants and includes many common weeds such as London rocket, sahara mustard, and black mustard but it also includes many of the crops grown here such as broccoli, cauliflower, cabbage, bok choy, kale, arugula, kohlrabi, mustard greens, daikon, and others. Almost all of the plants in this family are valued for their nutritional or medicinal properties. Even many of the weeds are used for medical purposes. Shepardspurse was frequently used during the first world war to control bleeding.

It can be difficult to control shepardspurse selectively in many brassica crops because of its similarity. It is the physical characteristics of this weed, however, that have been largely responsible for its spread. The foliage of shepardspurse is characteristically a low growing rosette that is often covered and can be difficult to reach with herbicides. The seedhead, on the other hand, grows 12 to 20” above the vegetative parts and has been reported to produce as many as 50 thousand seeds per plant in a single season. The seeds are very small and can float in water and blow in wind. They germinate at very shallow depths and soil active herbicides can fail if they are not concentrated at the soil surface.

Shepardspurse proliferated in alfalfa during the years when 2, 4-DB (Butoxone, Butyrac) was the primary broadleaf herbicide used because 2, 4-DB is ineffective on this weed. In vegetable crops, shepardspurse can be controlled with Kerb on the crops it is registered on if it is concentrated at the surface. It is less effective if some of the herbicide leaches below the germinating seeds. Prefar, Dacthal, Balan and Prowl are mostly ineffective on this weed.

Area wide Insect Trapping Network   VegIPM Update, Vol. 12, No. 19, Sep 22, 2021.
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts decreased slightly after a above average peak in activity for September; particularly active in Wellton and Roll.  
 
Beet armyworm:         
Trap counts decreased slightly in most locations, but well below average for September. Most activity in Wellton and Yuma Valley.
 
Cabbage looper:         
Cabbage looper trap counts down in all locations but remain quite active Wellton. Activity normal compared to previous years. 
 
Whitefly:                      
Adult movement increasing Dome Valley, but down in most other locations; movement is below average for this time of year. 
 
Thrips:                         
Thrips adult movement increased slightly in some locations, particularly in Wellton and Tacna, but remains below average for mid-September.
 
Aphids:                        
Aphid movement has been absent since early June typical with high summer temperatures, and the monsoon flow.  Expect activity to begin with N and NW winds.
 
Leafminers:                  
Adult activity remains decreased in mostr location and remains low; below average for this time of season.
 
Diamondback moth:    
Beginning to pick up a few moths in Dome Valley and Gila Valley; below average for September so far.