The Bagrada bug, Bagrada hilaris, first occurred on desert cole crops at damaging levels in the fall on 2010, and since that initial outbreak the invasive stinkbug has become a major pest of desert cole crops. In 2012, widespread infestations were reported throughout the desert growing area from September and into early November, comparable to the infestations growers experienced in 2010. Stand losses and yield/quality reductions to broccoli, cauliflower, cabbage and other Brassica crops were considered economically significant in some growing areas, albeit at lower levels than reported in 2010. Insecticide usage to control this pest remains high. 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 intensity of chemical management and severity of Bagrada bug infestations on direct-seeded and transplanted cole crops. A summary of the survey results can be found in the following report: Impact of the Bagrada Bug on Desert Cole Crops from 2010 - 2012: A Survey of PCA and Growers. Based on PCA estimates from the surveys, Bagrada bugs have occurred on greater than 85% of the direct seeded and transplanted cole crop acreage over the past 3 seasons. Similarly, almost all of these infested acres were treated with insecticides to control the pest. Averaged across all years, PCAs / growers reported treating direct-seeded crops for Bagrada bugs on a higher percentage of acres than where they reported that Bagrada bugs were present. On average, about 78.5% of the acreage was chemigated 1.6 times, and about 88% of the reported acres were sprayed an average of 2.3 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% since the initial outbreaks in 2010, likely a result of PCA awareness of the pest’s damage potential and better timing and use of chemigation treatments and foliar spray applications, as well as proper selection of effective products. 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.

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.

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.