Historically, our Areawide Pheromone and Sticky Trap monitoring for insects was terminated around the first of April as the produce season ended. Beginning 4 years ago however, we continued our Areawide Trapping Network throughout the summer to collect trapping data from all 15 areawide trap locations year-round.  So why is this additional trapping data useful? For several reasons: 

1) Understanding the activity of some of our key pests when produce is not grown during the summer may give us an indication of what to expect as the fall produce season begins. This may be particularly helpful for predicting moth flights and whitefly flights in August-September coinciding with early transplanting and direct seeded crops.  Another example is keeping track of corn earworm which can unexpectedly show up near the beginning of fall harvests. 
 
2) Trapping for pests during the summer has shown us that 2 of our more important produce pests are not caught in traps during the summer. We presume this is due to the absence of brassica crops and weeds for diamondback moth, and high daytime/nighttime temperatures lethal to aphids. The fact that trap catches resume in the fall supports our conclusion that these pests are absent in the summer, only to reenter the desert via winds and/or transplants in the fall. And finally, 

3) It gives me something to do in the summer other than write reports and papers. 
So, visit the Areawide Summer Trap Network if you’re curious what our key pests are up to.

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.

Weeds are a problem year after year even where they have been diligently controlled. A major reason for this is that weed seeds continually move into fields by irrigation water, wind, equipment, contaminated seed and other means. Controlling weeds on irrigation ditch banks can greatly help to reduce weed seed movement into fields. 

The EPA regards non-crop areas as those that are not dedicated to crop production. Although crops are not normally grown on irrigation ditch banks, these areas should not be managed as non-crop. Several very broad spectrum and long lasting herbicides are registered for non-crop areas which include roadsides, industrial sites, fence rows, around structures, railroads etc. Irrigation ditch banks should be considered separately because of their proximity to crop fields and irrigation water and the potential for herbicide movement into sensitive areas. 

It is important to read the label carefully and only use those products that are specifically allowed for use on ditch banks. Some products are restricted to drainage ditch banks or dry ditches. Some can be used only above the water line and some can only be used for non-irrigation ditch banks Because most ditches here are used for irrigation, this can be confusing. The definition of a ditch however, can include an open trench or natural channel. It can also include ditches that are not in use for long periods of time. Some labels specify how long this non-use period should be. Some herbicides that have been used on ditch banks in the past are now restricted from this use because of groundwater contamination or off target movement that has occasionally occurred. Do not assume that products that were used for ditch banks in the past can still be used. Even very old products like MSMA can no longer be used for irrigation or drainage ditches. The following summarizes how some of the more common products that have been used on ditches can be used although the product labels should be read for more complete directions. 

Aminopyralid (Milestone MVD) This is a broad-spectrum systemic herbicide. It is a growth regulator but not extremely volatile. It can only be used on “non-irrigation ditch banks”. 

Bromacil (Hyvar ,WSA 6 Weed Killer,others) Broad spectrum and very persistent. Can not be used where surface water is present. 

Dicamba (Banvel, Clarity ,others) Broad spectrum on broadleaf weeds only. This is a growth regulator that can be volatile,. Can not be used inside of irrigation ditches. Diuron (Karnex,Direx, others) Apply only when water is not present in the ditch.Must be fixed to the soil by moisture. Fill the ditch and let stand for 72 hours and then drain off. 

Diquat (Diquat, Reward) This is a contact herbicide that is inactivated by soil. Can be used in both irrigation and drainage ditches. 

Fluroxypr (Starane,Vista) This is a broad spectrum growth regulator that controlles broadleaf weeds only. Can only be used on non-irrigation ditch banks. 

2,4-D (many formulations and premixes) This is a very volatile plant growth regulator. Can be used on drainage ditches only and not where it might get into irrigation water. 

Imazypyr (Arsenal, Polaris, others) Broad spectrum herbicide with both soil and foliar activity. Not for use in irrigation ditches. 

Pelargonic Acid (Scythe) Contact herbicide with no soil activity. Can be used in dry ditches, canals and ditch banks above the water line. 

MSMA (Bueno 6, Ansar others) Can no longer be used on drainage or ditch banks. Broad spectrum contact herbicide. 

Triclopyr (Garlon, Turflon others) Broad spectrum growth regulator. Does not kill grasses. Can be volatile. Can not be used on irrigation ditch banks.

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 17, Aug 21, 2024
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:           
CEW moth counts decreased areawide; about average to previous years.
 
Beet armyworm:         
BAW moth counts are up in south Yuma valley and Dome valley; about average for August

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 decrease, average for this time of the year.
 
Thrips:                          
Thrips adult activity continues to decline, average for August.
 
Aphids:                       
Aphid movement is absent and consistent with what we typically see during the summer.
 
Leafminers:                  
Adult activity declining and average for August.