It sure feels like summer is finally over. Lots of Brassica transplants in the ground, and direct-seeded broccoli and lettuce plantings are establishing throughout the growing regions.  In the past week, I’ve observed or received reports from PCAs of key insect pests beginning to show up (or not) on melon and early produce crops in the desert.   
 
Seedling pests:  Flea beetles (FB) are beginning to show up in transplanted crops like they always do, but pressure has been light so far. We haven’t seen much in our experimental plots at YAC either.  Remember, FB adults lay eggs in the soil of their favored local host plants (i.e., alfalfa, cotton, purslane, pigweed and nightshade) where larvae feed on the roots to later emerge as adults. So, keep in mind, the source of that FB infestations hitting your new stands may not just be freshly cut hay, defoliated cotton, or disked weeds. Have had a couple reports of western stripped cucumber beetles in melons feeding on fruit and on cauliflower transplants feeding on new foliage.  Remember they are a lot like FB and can be best controlled with a neonic/pyrethroid combo (Endigo, Venom+Pyr). Bagrada bug:        No additional reports of bagrada bug adults in transplanted brassica fields yet, and have yet to see one in my broccoli at YAC yet. Fall populations have been very light over the past several years, but don’t fall asleep on these guys.  It’s still early and they might surprise you as the season progresses.   Look for those fresh feeding signs on cotyledons and young leaves.  Experience suggests that they are most abundant after the monsoon humidity breaks.
 
Lepidopterous Larvae (worms):   Worm pressure seems to be at or below normal depending on region. Areawide pheromone traps suggest that Beet armyworm moth activity is about normal (highest in Tacna/Roll/ Dome). Reports suggest they are most active in the field in the Roll/Wellton area right now.   Trap catches so far show that Cabbage looper moths are almost non-existent, and no reports on melons to date. They should pick-up as we approach October. But they will show up sooner or later, so get ready.  You have numerous insecticide alternatives at your disposal to control them.  So far,  Verimark transplant drenches appear to be providing expected residual control (25-30 days).   Have had a couple of reports of Diamondback moth larvae on newly transplanted brassica crops. Plants originated from coastal California. However, we’ve yet to capture moths on pheromone traps which suggests that adult immigration on high altitude winds has not occurred this season. Remember, DBM disappear each summer and reestablish on desert crops via transplants or migrate in on monsoon/tropical storms. I strongly stress that you check your Cole crops closely this fall, particularly on plants originating from coastal CA. Rumor has it that Salinas has been battling DBM for some time this summer. 
 
Whiteflies:       Reports in area melons range from light to moderate numbers so far, but there is still cotton out there yet to be picked. Numbers have bee unseasonally low at YAC in out experimental melons, and no signs of virus yet.  And adult numbers decreased dramatically in our experimental melons at the Ag Center over the weekend following the recent drop in temperature. Reports of light levels in early cabbage treated with Verimark.  Remember, you have several insecticide alternatives to control them in melons and produce.  
 
For more information on IPM approaches for these pests visit:

• Insect Pests at Stand Establishment, 2024
• Guidelines for Diamondback Moth Management in Desert Cole Crops, 2024-25
• Lepidopterous Larvae Control Chart 2024
• Whitefly Control Chart 2024

Chile (Capsicum annuum) production is an important aspect of vegetable crop production systems in the desert Southwest.  The Capsicum annuum species is the most common group of chiles that we encounter and these chiles are common in our southwestern diet.  The New Mexico type chile (aka, Anaheim) is a common crop in the desert Southwest including southeastern Arizona, southern New Mexico, west Texas, and northern Chihuahua, Mexico.
There are five domesticated species of chile peppers. 1) Capsicum annuum is probably the most common to us and it includes many common varieties such as bell peppers, wax, cayenne, jalapeños, Thai peppers, chiltepin, and all forms of New Mexico chile. 2) Capsicum frutescens includes malagueta, tabasco, piri piri, and Malawian Kambuzi. 3)Capsicum chinense includes what many consider the hottest peppers such as the naga, habanero, Datil, and Scotch bonnet. 4) Capsicum pubescens includes the South American rocoto peppers. 5) Capsicum baccatum includes the South American aji peppers (Guzman and Bosland, 2017).  Some examples are shown in Figure 1 and some other chile pepper species as well.

Figure 1.  Capsicum annuum pod types include A) Asian, B) Cayenne, C) Chile de Arbol, D) Chiltepin, E) Hungarian Paprika, F) Jalapeño, G) New Mexican, and H) Poblano.  A Capsicum baccatum pod type is I) Aji. Capsicum chinense pod types are J) Bhut Jolokia, K) Habanero, and L) Scorpion. A Capsicum pubescens
pod type is M) Rocoto and a Capsicum frutescens pod type is N)
Tabasco.  Source:  Guzman and Bosland, 2017.

Crop Phenology
Efficient management of a crop requires an understanding of the basic stages of plant growth in relation to time or age (crop phenology) and basic crop needs.  There is a strong phenological relationship with morphological and physiological changes that are taking place and the input requirements important for the crop as the plant develops.  As plants change physiologically and morphologically through their various stages of growth, water and nutritional requirements are great examples of crop demand changes that should influence management of the crop in the field.   
 
Heat units (HUs) can be used as a measure of “thermal time” that drives plant development.  Thus, HUs can be used as an important management tool for more efficient timing of irrigation and nutrient inputs to crop and pest management strategies.  Plants will develop over a range of temperatures which is defined by the lower and upper temperature thresholds for growth (Figures 2 and 3).  
 
Heat unit systems consider the elapsed time that local temperatures fall within the set upper and lower temperature thresholds and thereby provide an estimate of the expected rate of development for the crop.  Heat unit systems have largely replaced days after planting in crop phenology models because they consider day-to-day fluctuations in temperature.  People still use days after planting to estimate stages of crop development but HUs are more accurate and reliable.
 
Crop phenology models describe how crop growth and development are impacted by weather and climate and provide an effective way to standardize crop growth and development among different years and across many locations (Baskerville and Emin, 1969; Brown, 1989).  
 
The use of HU-based phenology models is particularly important and applicable in irrigated crop production systems where water is a non-limiting factor.  Water stress will alter phenological plant development and it is a major source of variation in crop development models.  Accordingly, irrigated systems are more consistent in crop development patterns and HU models can be much more consistent and reliable.
 
Chiles are a warm season, perennial plant with an indeterminant growth habit that we grow and manage as an annual crop.    The fruiting cycle begins at the crown stage of growth and continues until the plant reaches a point of “cut-out” with a hiatus in blooming as the plant works to mature the chile fruit crop that has been developed.  
 
Figure 4 describes the basic phenological baseline for New Mexico – type chile and was developed from field studies conducted in New Mexico and Arizona (Silvertooth et al., 2010 and 2011; Soto et al., 2006; and Soto and Silvertooth, 2007).  The use of HUs (86/55 ^oF thresholds) are applied in this development model since chiles are a warm season plant (Figures 2 and 3).
 
Heat units accumulated after planting (HUAP) for any date of planting to the present date can be easily accessed in the Arizona Meteorological Network (AZMET) website.
 
https://azmet.arizona.edu/
 
Also, the new HUAP tool for cotton that Dr. Jeremy Weiss, AZMET Director, recently developed can be used for chiles or other warm season crops.  The same 86/55 ^oF thresholds are used and the model does not know what crop you are working with.  It is a quick and easy way to calculate HUAP totals for any planting date in 2024.
 
https://viz.datascience.arizona.edu/azmet/cotton-growth-stages-and-heat-units/

Figure 2.  Typical relationship between the rate of plant growth and development
and temperature.  Growth and development ceases when temperatures decline
below the lower temperature threshold (A) or increase above the upper
temperature threshold (C).  Growth and development increases rapidly when
temperatures fall between the lower and upper temperature thresholds (B).



Figure 3.  Heat unit calculation with the sine curve method using upper and
lower temperature thresholds (Brown, 1989).  The 86/55 ºF thresholds are used,
consistent with most warm season crops.


Figure 4.  Basic phenological guideline for irrigated New Mexico-type chiles.

References
Baskerville, G.L. and P. Emin.  1969.  Rapid estimation of heat accumulation from maximum and minimum temperatures. Ecology 50:514-517.
Bosland, P.W., E.J. Votava, and E.M. Votava. 2012. Peppers: Vegetable and spice capsicums. Wallingford, U.K.: CAB Intl.
Brown, P. W.  1989.  Heat units.  Bull. 8915, Univ. of Arizona Cooperative Extension, College of Ag., Tucson, AZ.
Guzmán, I. and P.W. Bosland. 2017. Sensory properties of chile pepper heat - and its importance to food quality and cultural preference. Appetite, 2017 Oct 1;117:186-190. doi: 10.1016/j.appet.2017.06.026.
Silvertooth, J.C., P.W. Brown, and S. Walker. 2010. Crop Growth and Development for Irrigated Chile (Capsicum annuum). University of Arizona Cooperative Extension Bulletin No. AZ 1529
Silvertooth, J.C., P.W. Brown and S.Walker. 2011. Crop Growth and Development for Irrigated Chile (Capsicum annuum). New Mexico Chile Association, Report 32. New Mexico State University, College of Agriculture, Consumer and Environmental Science.
Soto-Ortiz, Roberto, J.C. Silvertooth, and A. Galadima. 2006.  Crop Phenology for Irrigated Chiles (Capsicum annuum L.) in Arizona and New Mexico. Vegetable Report, College of Agriculture and Life Sciences Report Series P-144, November, University of Arizona.
Soto-Ortiz, R. and J.C. Silvertooth.  2007. A Crop Phenology Model for Irrigated New Mexico Chile (Capsicum annuum L.) The 2007 Vegetable Report. Jan 08:104-122.

This study was conducted at the JV farms at Gila Valley. Lettuce ‘Raider’ was seeded, then sprinkler-irrigated to germinate seed on September 27, 2021, on double rows 12 in. apart on beds with 42 in. between bed centers.  All other water was supplied by furrow irrigation or rainfall. Treatments were replicated four 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 Jan 6, 2020 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.

 
Fusarium wilt (caused by Fusarium oxysporum fsp 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. Readings for germination was taken o on October 5, 2021 and October 22^nd 2021. Disease scoring/rating was done on 10-23-21. 
 
The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. Plant vigor was normal and phytotoxicity symptoms were not observed in any treatments in this trial.

Given the positive feedback from last week’s article, I thought I’d share with you another video that showcases the cutting-edge advancements in AI technologies. This time, the topic is Digital AI Twins. Reid Hoffman, a renowned expert in AI technologies, has created a digital twin of himself named “Reid AI” using a custom Generative Pretrained Transformer (GPT). Reid AI was trained using content from over two decades worth of Hoffman’s public speeches, podcasts and published books. The result is a digital entity that mirrors Hoffman’s knowledge, insights, and even his conversational style. In the segment, Hoffman interviews his AI counterpart. The conversation is not only entertaining but also very realistic, blurring the lines between human and machine. I was pretty impressed and think you will be too. Given the rapid advancements in these technologies, one can’t help but wonder what’s next in the evolution of AI and how this technology will change the world.

Check it out here or by clicking image below.

Fig. 1. Reid Hoffman meets his AI twin. (Credit: Reid Hoffman).

In a letter from the EPA to AMVAC dated May 2, 2024 that you can find by clicking here: https://www.regulations.gov/document/EPA-HQ-OPP-2011-0374-0116 EPA "thanks AMVAC for voluntarily proposing to discontinue DCPA use on onions".
If DCPA is not available next season our options for onion weed control are reduced. Please read the work from Carl Bell https://escholarship.org/content/qt91w4d06x/qt91w4d06x.pdf?t=lnryxp&v=lg regarding combining bensulide and pendimethalin for weeds control  in onions. He did this research due to a similar situation with Dacthal in 1996.
We tested last season 2 qts of Prefar and 0.5 pt of Prowl and the weed control looked promising.  There appears to be a synergystic effect between these products. Some phytotoxicity was observed and stand was affected. Bell reported (2001) that "a reduced crop stand does not always equal a reduced yield, since onions compensate to some extent by producing larger bulbs". 

Some PCAs are planning IPM strategies and are suggesting for green onions: "Apply Goal  early post emergence with clethodim if you have grasses then Prowl at layby".
What do you think? keep sending your comments to the Veg IPM Team and let us know what you think.

The push-pull strategy, a stimulo-deterrent diversionary strategy, combines behavior-modifying stimuli that manipulate the distribution and abundance of insect pests and/or natural enemies. When your main crop is intercropped with plant species that can mask the host (main crop) appearance or emit undesirable volatiles (smells) that divert the pests away from the main crop (push), on the other hand, other plants in your intercropping system can be extremely attractive using stimuli that are highly apparent and attractive to the pest, hence trapping the pest (pull) (Fig. 1). Insects use visual, chemical, or tactile cues. Thus, by intercropping the main crop with plants that emit more attractive smells, are more visually appealing, or release undesirable smells, one can cause the pest to be trapped and repelled from the main crops, resulting in effective control of the pests.

Figure 1. Pictorial representation of push-pull strategy. 

In Brazil, the push-pull strategy has been found effective in managing major kale pests. They found that using mustard as a preferred host pulled the pests away from the kale crops, while marigold plants increased the beneficial arthropod population which provided additional control of the pests (da Silva et al. 2022; https://www.sciencedirect.com/science/article/pii/S1049964421003029). My 

lab plans to evaluate the efficacy of similar systems for insect pest management in organic vegetable crops in Arizona. 

In Salinas, California, intercropping lettuce with sweet alysum has favored some measurable aphid control. Sweet alyssum attracts and feeds hoverflies, which then lay eggs in lettuce, producing hoverfly larvae that consume aphids. In this video, Dr. Brennan describes in detail how this system works. This research was conducted about a decade ago, but I believe this could be an important tactic to consider for aphid control in lettuce. We also plan to evaluate this system for aphid management in lettuce in Arizona lettuce growing regions. 

Figure 2. Graphical representation of Lettuce-Alyssum intercropping system for aphids control. (Image source: Brannan 2013). 

Area wide Insect Trapping Network   VegIPM Update, Vol. 15, No. 21, Oct 16, 2024

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: CEW moth counts increased in most traps; about average for early October.

Beet armyworm: Trap counts increased in most areas last week, and about average for early October.

Cabbage looper: Cabbage looper trap counts still most locations, below average for this time of the season.

Diamondback moth: Adult activity increasing, particularly in the Yuma and Dome Valleys.  Above average for this time of season.

Whitefly: Adult movement increasing Tacna, Dome Valley and Yuma Valley; overall about average for early October.

Thrips: Thrips adult movement picking up in all areas, overall activity above average.

Aphids: Winged aphids beginning to show up the north Yuma and Gila Valleys; about average for early October.