Aphids are beginning to show up on cole crops and it won’t be long until they begin to colonize leafy vegetables. In late October of this year, the USEPA reestablished the registration for products containing sulfoxaflor (IsoclastTM Active), namely Sequoia® for season long use on Leafy Vegetables (Group 4) and Brassica(Cole) Leafy Vegetables (Group 5). This reestablished label refers to most, if not all, winter vegetables produced in the desert. The label for these crops is essentially the same as it was before the cancellation but with a couple of restrictions. The new registration requires that a 12-foot in-field, downwind buffer must be maintained from blooming vegetation during application. It also restricts tank-mixing with products containing certain active ingredients. The list of prohibited tank-mix partners can also be accessed at http://isoclasttankmix.com. This is good news for PCAs and growers as we move into the winter and spring produce season. In addition to Sequoia, PCAs can achieve good residual aphid control using Movento as a foliar spray and should be rotated with Sequoia and other insecticides when aphid pressure is heavy. Imidacloprid soil applications (at planting) also provide residual control, but will often require additional foliar sprays near harvest. Foliar alternatives such as Assail, Sivanto, and Beleaf are good aphicides also, but do not provide the same level of residual control as either Sequoia or Movento. Under heavy aphid pressure, PCAs should be prepared to use several of these alternatives, rather than rely on only one product. Sequoia also provides good control of Lygus bugs on crops such as celery and lettuce, and should be rotated with other products such as Beleaf, Vydate and Acephate. For more information on insecticide alternatives for aphid management see our 2016 Aphid Control Chart. 

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.

Based on last week’s weather, it’s officially summer in my book. Things seem to be slowing down, so I thought I’d change pace this week and take the opportunity to ask you, the readers of this newsletter, if there are any topics you are interested in hearing more about. I am happy to do some research and try to find some answers. Drop me a line at siemens@cals.arizona.edu or feel free to call me at 928.782.5869. I’d love to hear from you.

Yuma Weather

Clovers can be very difficult to control weeds here, but it is also a major crop and common ornamental. Clovers can survive under poor growing conditions and are not controlled with glyphosate and seem to get worse every year. There are more than 50 types and 300 species of clover and they can be easily misidentified. They are all in the legume (Fabracea) family and can use a bacterium (rhizobium) in the soil to convert nitrogen in the atmosphere to a form that they and other plants can use for fertilizer.    There are only 4 or 5 clover species that are agricultural pests here. The ones we get the most questions on are white and yellow sweet clover. These are in the Melilotus family. White sweet clover (Melilotus albus) is tall for a clover and can get 3 to 5 foot in height. The leaves are thinner than most clovers and this difficult to control weed lives at least 2 years and sometimes longer. Glyphosate and most of the contact herbicides do not control it. The plant growth regulator herbicides work best. Yellow sweet clover (Melilotus officinalis) is less common here. The flowers are yellow, and it is not as tall and vegetative as white sweet clover. Yellow is more common at higher elevations.   California burclover (Medicago polymorpha) and Black medic (Medicago lupina) are in the same genus as alfalfa and are more of a problem in landscapes, parks and golf courses than in agricultural fields here. They do not grow upright and spread below the crop or turf. The true clovers are in the Trifolium genus and include white and strawberry clover. These creep along the ground and root at the nodes of the stem. These are more of a urban landscape weed and not considered an agricultural problem. Creeping woodsorrel or Oxyalis looks like a clover but it is not related. It is a turf weed that spreads rapidly along the ground and can live for several years. Preemergent herbicides are effective against all these clovers before they become established. The postemergence herbicides that are most effective in controlling these clovers are the plant growth regulators. Contact herbicides and glyphosate are generally ineffective.

Summer Insect Trapping Network   
 

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 14, July 10, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth counts decreased to seasonal lows comparable to previous years.
 
Beet armyworm:         
BAW moth counts decreased to seasonal lows comparable to previous years.
 
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 melons harvests and field disking.
 
Thrips:                          
Thrips adult activity declined significantly, comparable to previous summers.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                   
Adult activity slightly above average for early July.