Historically, our Areawide Pheromone and Sticky Trap monitoring for insects was terminated around the first of April as the produce season ended. Beginning 2 years ago however, we continued our Areawide Trapping Network throughout the summer to collect trapping data from all 16 areawide trap locations year-round.  So why is this additional trapping data useful? For several reasons. First, 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. Secondly, 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, it gives me something to do in the summer.  So, visit the Areawide Summer Trap Network if you’re curious what our key pests are up to. We also continue to monitor thrips activity during the summer. This involves plant sampling using a dislodgement sampling method (beat pan) to determine the relative abundance of thrips adults and larvae on alfalfa, cotton, melons, wheat, Sudan grass, and weeds.  This is being conducted to supplement our yellow sticky trap data that only indicates thrips adult flight movement an area. With this plant sampling we should be able to determine the primary host plants thrips are colonizing in the cropping season during the long hot summer. We are also trying to determine whether these crops allow for the reproduction of thrips. So far, all the crops and weeds we have sampled have shown that thrips will reproduce and complete their life cycle on them. This is important, particularly for weeds, as we are trying to determine whether INSV can be survive the summer in the absence of lettuce. It is also important because it allows us to determine potential exposure of thrips to key insecticides like Radiant and Lannate for resistance management purposes. These crops essentially serve as untreated refugia that likely sustains insecticide susceptibility and is the reason these products are still effective against thrips.  We will be conducting this work throughout the summer, as well as through next produce season. We will periodically provide updates of these thrips monitoring results throughout the summer.  As my dad used to say, “to solve the problem, you must first understand the problem”.

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.

Common Purslane (Portulaca oleracea) is at the same time one of the most troublesome weeds in vegetable crops and one of the most nutritious leafy vegetables. It is very widespread in the desert southwest but is also on the list of Arizona Prohibited Noxious Weeds which means that it is prohibited from entry into the state. Common Purslane is eaten in Mexico (Verdolaga), Europe and Asia and contains more omega 3 fatty acids than any other leafy vegetable. It also contains vitamins A, B and C and dietary minerals.

Common Purslane is often lumped together with Horse Purslane although the two are in different families. Common Purslane is in the Portulaca family while Horse Purslane is in the Trianthema or Carpetweed family.

In lettuce, Purslane is often controlled during ground preparation where it is geminated and killed with chemicals or tillage. Timing is important with both of these techniques. Purslane grows rapidly and one plant can produce thousands of seeds. These seeds can germinate in 12 hours after receiving moisture in August and September. They can also germinate in January and February but will take 3-7 days to germinate at that time. The stems are very succulent and unless they are completely killed and desiccated they can reroot at the nodes. Tillage that does not completely desiccate the plants can spread rather than eliminate this weed.

Herbicides used to kill this weed during ground preparation include both contact (Gramoxone, Aim and ET) and systemic (glyphosate) herbicides. Results can range from 0 to 100% depending upon weed size, rate and adjuvant used at the time of application. The contact herbicides can produce almost 100% control when the Purslane is less than 2 inches in diameter and less than 50% control when larger than this. This is especially the case with Aim where control can drop from excellent to poor in 3 - 5 days.

Purselane has a thick waxy cuticle and an adjuvant is needed with all of these herbicides to help penetrate into the leaves and stems. A non-ionic surfactant will help the herbicide spread and stick while crop oil concentrates help break up this waxy layer. Time of day when applied can also be important. During the morning hours leaf pores are open, new growth is occurring and the plant is more sensitive to herbicides than during the middle of the day when the plant is conserving water and energy. There is a wide range of rates used with Aim, Gramoxone and glyphosate to control Purslane during ground preparation. Normal rates vary from 0.5 to 2.0 oz. with Aim, 1.5 to 4.0 pt. with Gramoxone and 1.0 pt. to 2.0 qts. with glyphosate when used alone or in combination. All of these herbicides only work on emerged weeds and people often wait until they are sure most of the weeds have emerged to avoid making multiple applications. As a result, there can be a wide range of weed sizes at the time of application. Rates should target the largest weeds. It is less costly to choose a higher initial rate than to have to make additional applications.

Area wide Insect Trapping Network   VegIPM Update, Vol. 14, No. 24, Nov 1, 2023            
 
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:            
CEW moth captures have steadily decreased over the past 2 weeks, and areawide about average for late-October.
 
Beet armyworm:         
Trap counts reached their highest levels so far this season, particularly in Tacna, Wellton and Yuma Valley, and about average for late October.
 
Cabbage looper:           
Cabbage looper numbers decreased areawide, and are still below average for this time of the year.
 
Diamondback moth:   
Sporadic DBM activity in low numbers throughout the area, trending well below average for late October.
 
Whitefly:                     
Adult movement increased in the past 2 weeks and above average for late October.
 
Thrips:                           
Thrips adult activity peaked in the last two weeks, and trending below average in October.
 
Aphids:                        
Winged adults continue to be captured for the season, consistent with heavy winds from W-NW. Aphid captures thus far have been well below average. 
 
Leafminers:                  
Adult activity decreased in most areas, and trending about average for late October.