We recently conducted our annual bagrada bug survey of growers and PCAs to estimate the impact of this new pest on desert cole crops. The bagrada bug, Bagrada hilaris, first occurred on desert cole crops at damaging levels in the fall on 2010, and since that initial outbreak it is clear that the invasive stinkbug has become an established pest of desert cole crops. In 2013, widespread infestations were reported throughout the desert growing area from September to well into November, comparable to the infestations growers experienced in the previous three years. Stand losses and yield/quality reductions to broccoli, cauliflower, cabbage and other Brassica crops were considered economically significant in most growing areas, and were reported at levels comparable to 2010. Insecticide usage to control this pest remains high, and consists mainly of pyrethroid chemigations and foliar sprays. In an attempt to document these impacts, we have surveyed produce growers and PCAs from Yuma, Imperial Valley and central Arizona on an annual basis since 2010 to estimate the severity of Bagrada bug infestations on direct-seeded and transplanted cole crops, and the intensity of chemical management. A summary of the 2014 survey results can be found in the following report: Impact of Bagrada Bug on Desert Cole Crops. Based on PCA estimates, bagrada bug infestations have been present on greater than 85% of the direct seeded and transplanted cole crop acreage over the past 4 seasons. In direct seeded crops, a greater % of the acreage was treated for bagrada adults than were infested. This is not surprising given the preventative nature of controlling bagrada infestations in order to reduce stand losses and plant injury. On average, about 80% of the acreage was chemigated 1.6 times, and about 88% of the reported acres were sprayed an average of 2.4 times in direct seeded-crops. When the number of chemigations and foliar sprays are combined over all three years, almost 4 insecticides applications were made to control this pest. Damage from bagrada bug infestations at stand establishment in both direct-seeded and transplanted crops has decreased by more than 50% from 2010 to 2012, but increased in 2013. PCAs also provided information on insecticides that provided effective control through both chemigations and foliar sprays. In general, they reported that products that have contact activity (i.e., Pyrethroids, OP/Carbamates) appeared to provide the most effective control against bagrada adults on both direct-seeded and transplanted cole crops. Overall, the results of the PCA survey are consistent with results obtained in research trials conducted at the Yuma Agricultural Center over the past three years.

This study was conducted at the JV farms at Gila Valley. Lettuce variety ‘Guapo’ was seeded, then sprinkler-irrigated to germinate seed on September 19, 2023, on double rows 12 in. apart on beds with 42 in. between bed centers.  Rest of the irrigation 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 on October 9, 2023 at the 3-4 leaf stage to a 12-inch spacing. Treatment beds were separated by single nontreated beds. Treatments were applied by incorporating in soil before seeding or with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart.

Month	Max	Min	Avg	Rain
September	100	71	86	0.71 in
October	93	61	77	0.00 in
November	80	51	65	0.08 in
December	71	44	57	0.82 in

 
Fusarium wilt (caused by Fusarium oxysporum f. sp. lactucae ) rating was done in the field by observing the typical symptom of lettuce wilt. Confirmation was done by cutting the cross section of roots. Disease scoring/rating was done on December 6, 2023. 
 
The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. The disease pressure was extremely high in 2023, and most treatments showed little or no control against the disease. The treatments that showed some activity were Bexfond, Cevya, Rhyme, and Serifel. Plant vigor was normal and phytotoxicity symptoms were not observed in any 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

Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts peaked about 2 weeks ago, but declined areawide this week. About average for October.
 
Beet armyworm:         
Trap counts increased in most locations, but remain well below average compared to previous years.
 
Cabbage looper:          
Cabbage looper up in most traps, particularly active in Yuma Valley and Wellton. About average for this time of season.
 
Diamondback moth:      
DBM moths peaked about 2 weeks ago (Dome and Wellton); below average for this time of the year.
 
Whitefly:                      
Adult movement increased in the past 2 weeks, particularly in areas near melons but remains below average for this time of year. 
 
Thrips:                           
Thrips adults increased markedly in many locations (Tacna, Dome, Yuma Valley), and currently about average for October.
 
Aphids:                        
Aphid movement beginning; light numbers in North Yuma Valley and Tacna. Below average for October.
 
Leafminers:                  
Adult activity up in a few locations (Yuma Valley), below average for September.