Western flower thrips are now beginning to increase on produce crops throughout the area. This is evident from sample collected here at the Yuma Ag Center and by the increase in areawide trap catches (see Areawide Trap Insect Network). They have slowly been increasing in the Yuma Valley, and should likely continue to increase as the days grow longer. The recent rainfall we had last weekend may temporarily reduce numbers, but don’t expect that to last very long. Based on historical data, if temperatures remain moderate and rainfall is light we can expect thrips numbers to reach high levels by the mid-March and into April (see graph below). Another factor PCAs should be concerned with this time of the year is thrips "bioconcentration" which occurs each year in March as lettuce acreage declines. This could be especially important this season since the abnormally warm temperatures appear to be pushing lettuce harvests ahead of schedule relative to years past. Each time a lettuce field is harvested and disked, adult thrips populations disperse from these areas into the next available lettuce field. This is generally coincident with our seasonally warm temperatures that are suitable for thrips development. As the number of lettuce acres becomes reduced near the end of the season, this creates a bottleneck effect that concentrates high numbers of thrips adults on the remaining fields under production. This can often make chemical control very difficult, particularly in March, as thrips adults may continually re-infest fields following spray applications. Furthermore, by mid-March when most of the lettuce production is finished, these populations can pose a threat to seedling cotton. Note: the key to preventing thrips from significantly scarring leafy vegetable plants is to prevent immature populations from becoming established. For more information on the management of thrips on desert produce please see the Thrips Control Chart 2015. 

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.

The autonomous agricultural robot industry is an incredibly fast-moving space. Startups, established companies and academic researchers are continuously putting forth new ideas and products. It’s hard to keep up with. In November of 2020, Future Farming (Misset Publisher, BV, Doetinchem, Netherlands) published a Field Robots Catalogue that provides a comprehensive overview of the state of autonomous ag robots. The article provides brief summaries of 35 autonomous ag robots that are currently commercially available. Along with a brief paragraph about what each robot does, the article presents information about how many robots from a particular manufacturer are actively being used, the cost of the machine, and links to a video of the device in action. Most of the robots are for weed management in vegetable crops. Kill mechanisms range from spot spraying to mechanical weed removal to electrocution.  Several of the robots featured are applicable and relevant to Arizona vegetable production, and some are currently operating in the U.S. If you’re interested in ag robots and want to get up to date, this article is an excellent resource and quick read. The article can be found at the link provided below.

Title: Future Farming Field Robots Catalogue
https://misset.com/field-robots/field-robots/
Publisher: Misset Publisher, BV, Doetinchem, Netherlands.

Contact herbicides are those that only affect the part of the weed that they “contact” They don’t move into or affect any other part of a plant. They were the first herbicides used and surprisingly, they still are better at controlling some weeds than any other products that have been developed. They usually control only small weeds with good coverage although some of them will kill large malva , Purslane and some other difficult to kill weeds. Goal, Sharpen, Treevix and Gramoxone, which are all contacts, will kill malva and purslane while systemic herbicides like Glyphosate and 2,4-D, misses them. Maestro or Bucril (Bromoxynil), also an old contact, will kill swinecress while many systemics like the growth regulators ,miss it. Glufosinate( Liberty, Rely) is a contact that is very broad spectrum and kills more grasses and broadleaves than many systemic herbicides. These all work very fast and in this age of immediate gratification ,you don’t have to wait long.  Most have little soil residual activity (except Goal, Chateau and a couple others) Goal and Chateau are contacts but used mostly preemergence to the weeds. They “ contact” the weeds when they emerge at the surface. which is a benefit where double or triple cropping is common. Most( again except Goal) are not volatile but will cause pretty clear contact injury when the spray moves to sensitive crops. Paraquat was registered in 1959 and is still a very useful tool for desiccating plants. Many restrictions have been put on its use because of its toxicity to humans.  Most contact herbicides are non-selective and will injure most living plant tissue. They are used selectively with directed spray or timing. Adjuvants are often required to increase absorption, spreading and sticking.

Area wide Insect Trapping Network   VegIPM Update, Vol. 12, No. 18, Sep 8, 2021.
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts increased in the past two weeks particularly in Wellton and Roll.  
 
Beet armyworm:         
Trap counts beginning to increase in most locations especially in dome Valley and the south Yuma Valley.
 
Cabbage looper:          
Cabbage looper increased in all locations particularly in Wellton, Dome and N. Yuma Valleys consistent with reports of eggs in the in the field.
 
Whitefly:                      
Adult movement increasing in all locations and particularly in Dome/Wellton; about average for this time of year. 
 
Thrips:                         
Thrips adult movement remains about average for early September.
 
Aphids:                         
Aphid movement has been absent since early June typical with high summer temperatures, and the monsoon flow.  
 
Leafminers:                  
Adult activity remains similarly low, above average for this time of season.
 
Diamondback moth:   
First record of DBM adults since early June. Are appearing sooner than last season, likely from high altitude winds associated with Tropical Storm Nora experienced last week.