One of the key questions we’ve had concerning bagrada bugs since it first arrived in the desert 5 years ago is where does the small stinkbug spend it’s summers? We obviously know where they are from September until late May; in cole crops and brassica seed crops. However, we have never been quite sure where they go after the last seed crop is harvested. Fortunately, we’ve learned much about the seasonal ecology of bagrada in the past few years, and this past week I received a number of reports from PCAs of bagrada bug adults being found in sweep net samples in cotton from the Gila and Yuma Valleys. These recent bagrada sightings are reminiscent of reports during the summer of 2010 when finding bagrada adults in cotton was very common throughout the summer. These recent reports are also not surprising considering that unpublished research conducted at the University of California, Riverside by Drs. Tom Perring and Darcy Reed has shown that adult bagrada bugs are capable of using non-brassicaceous plants (Sudan grass, Bermuda grass, corn, and cotton) to survive for extended periods in the absence of brassicaceous host plants (e.g., broccoli, cauliflower). They found that bagrada adults can survive for longer than 90 days on cotton, 60 days on Bermuda grass, and 30 days on corn and Sudan grass. Furthermore, Sudan grass and Bermuda grass were shown to support multiple generations of bagrada in greenhouse studies, although generation times of the insect were much longer than on broccoli. Based on their research and anecdotal observations by myself and others in Yuma, I’ve concluded that these common summer crops should be considered key sources of bagrada bug infestations for fall cole crop plantings. So you might want to keep this information in mind and pay close attention as you’re sampling cotton and other crops this summer. If by chance you find bagrada on any of these crops, please let me know. Learning more about how this pest bridges the brassica-free, summer months should lead to a better understanding of how to effectively manage it in the future. For a comprehensive review of the biology, ecology and management of the Bagrada bug please view this paper Bagrada hilaris (Hemiptera: Pentatomidae), An Invasive Stink Bug Attacking Cole Crops in the Southwestern United States. .

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.

For those of you interested in the latest developments in Vegetable IPM and/or in need of CEU’s, Yuma County Cooperative Extension has created online workshops that offer CEU and CCA credits for both AZ and CA. Current offerings are the recorded workshops from 2021 Southwest Ag Summit. There’s an ag mechanization session entitled “Advances in Weed Control Technologies”, and several others that readers of this newsletter may be particularly interested in including: “Integrated Pest Management Regulatory Update” “Pesticide-Related Updates: The Latest Presented by the Greatest” “Influence of Irrigation on Insect, Weed, and Disease Management” “Advances in Weed Control Technologies” “Integrated Pest Management in Vegetables”. Please recognize Yuma County Cooperative Extension Agricultural Agent Robert Masson who spearheaded this effort. Click on the image, or here to access Veg IPM workshops online.

Weeds that are outside of fields can still be harmful to crop production. This does not include ditch banks or fallow fields. Non-crop weed control includes weeds around buildings, roadways, equipment yards, fence lines etc. It is different than fallow ground or ditch banks weed control and includes places where crops are not grown. Weeds in non-crop areas can be a source of weed seeds that blow or are carried into places where crops are grown. They can also be a refuge for insects,  diseases and rodents. The reason that these herbicides are registered for non-crop areas is that they are broad spectrum and persistent. Some are registered for use in fields but at much lower rates than for non-crop areas. For instance, Diuron can be used on alfalfa at 1 to 1.5 qts/ac. but is used for non-crop areas at 12 qts/ac.

Herbicide	Weeds Controlled	Activity	Soil Residual	Comments
Bromacil	Broadleaves and grasses	Preemergence	1 to 2 years	The nuclear option Should be incorporated with water. Keep away from roots of desirable vegetation.
Hexazinone	Broadleaves and grasses	Preemergence and Postemergence	1 to 2 years	Keep away from roots of desirable vegetation. Incorporate with water.
Diuron	Broadleaves and grasses	Preemergence and Postemergence	2 years	Incorporate with water but do not leach into roots of desirable vegetation
Prometon	Broadleaves and grasses	Preemergence and Postemergence	1 to 2 years	Must be incorporated with water
Tebuthiuron	Broadleaves and grass. Good on hardwood trees	Preemergence and postemergence	2 years	Incorporate with water. Contact with even on feeder root of desirable vegetation can be lethal
Imazapyr	Broadleaves and grasses	Preemergence and post emergence	1 year	Primarily a postemergence herbicide but is readily absorbed by rootsif incorporated with water
sulfometuron	Broadleaves and grasses	Preemergence and post emergence	1 year	Must incorporate with water
Aminopyralid	Broadleaves	Preemergence	1 year	broadleaves only. Shorter soil residual for weeds but crops can not be planted for 1-2 years

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 19, Sep 18,2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts low in most traps; below average for this early produce season. 
 
Beet armyworm:         
Trap counts high in Tacna and Wellton, and about average for early September
 
Cabbage looper:           
Cabbage looper trap counts low in all locations, typical for early September.
 
Diamondback moth:    
Adult activity not picked up in traps yet.  Overall, typical of early September with minimal Monsson activity.
 
Whitefly:                      
Adult movement most active in Dome Valley and S. Yuma Valley; overall below average for early September
 
Thrips:                          
hrips adult movement beginning to increase in Tacna and dome; overall activity typical for early September. 
 
Aphids:                         
Aphid movement absent so far; anticipate activity to pick up when winds beginning blowing from N-NW. 
 
Leafminers:                 
Adult activity light in all areas, about average for this time of season.