Hope you are all enjoying the summer so far and keeping busy. Although, we’re about 2 months away from the Fall produce season, it’s never too early to begin thinking of IPM strategies you will be using to battle key insects next season. This includes keeping track of their typical activity during June, July, and August. Below is a short discussion detailing individual pests. 
 
Aphids:    The major aphid species that are important in produce crops each spring include green peach aphid, foxglove aphid and lettuce aphid.  These species are considered cool season pests and are biologically most active during the winter and spring when temperature average around (55-65 F). We do not find them on summer crops as the high temperatures prohibit their activity. They essentially become extinct each summer only to reappear in the fall to infest crops in Oct-Dec migrating into the desert via N-NW winds that occur after the monsoons.
 
Diamondback Moth (DBM):  Another key pest that disappears each summer but for a different reason than for aphids. The host range of DBM is limited to only brassica crop and plants. Although brassica weeds are common during the winter, they occur during the summer due to high temperatures and dry conditions. Thus, like aphids, DBM populations from the previous spring season become “extinct” during the summer when brassica crops and weeds are absent. They reappear each fall migrating in on high winds associated with tropical storms from Mexico, or arrive into the region on infested brassica transplants from California.
 
Whiteflies:       A resident pest that occurs year-round in the desert. As a warm season pest, whiteflies are most abundant on fall produce crops, and seldom a problem during the winter and spring. Peak abundance occurs during the summer months on cotton, and again in September and October on fall brassica, leafy vegetables and fall melons.  Thus, it is important to control whiteflies in cotton prior to defoliation to prevent large migrations onto fall produce crops. In addition, whiteflies can be found on several weeds such as purslane, goosefoot, ground cherry, and sunflowers. Sanitation in and around fields being prepped for fall plantings is important. Preventatively, growers should consider applying soil, system insecticides such as imidacloprid or Verimark to Fall produce crops.

Beet Armyworm (BAW):  A warm-season pest that occurs year-round in the desert. They tend to reach peak abundance twice a year. Generally, the most important peak is in September and October when weather is ideal for their development, flight activity and oviposition. A second peak occurs in late spring. Activity is generally light during the summer, occurring primarily in alfalfa crops. Although BAW is known to migrate in from the south via monsoon and tropical storms, resident populations annually occur in alfalfa during the summer. Thus, to minimize BAW in fall produce crops, thorough management of BAW can potentially minimize their movement onto Fall produce crops.  Weeds are also a source of BAW (purslane, goosefoot, sunflower and Russian thistle) so sanitation in and around fields is important.
 
Western Flower Thrips (WFT):  Also a resident pest that can be found in the desert year round. WFT is most abundant on lettuce in the late spring, but peaks in abundance on alfalfa, melons and cotton is May and June. During the late summer numbers drop dramatically where thrips can be found on melons and alfalfa and weeds like goosefoot and purslane. WFT slowly move into lettuce again in early fall and are least abundant during the winter.  Sanitation of weeds during the summer can help reduce thrips abundance moving into the fall crops and weeds.
 
For more information see:   Keeping Track of Major Produce Pests During the Summer

Southwester Chile Production
The Southwestern (SW) Chile Belt extends from southeast Arizona, across southern New Mexico, into far-west Texas, and northern Chihuahua, Mexico.  The SW Chile Belt is dominated by production of New Mexico-type chile, also commonly referred to as “Hatch chile” and also sometimes referred to as “Anaheim” type chile.  
Recent acreages across the SW Chile Belt have consisted of approximately 7-8,000 acres in NM, 3-4,000 in TX, approximately 90,000 acres in Chihuahua, and about 300-500 acres in Arizona.  Chiles are often associated with New Mexico, but Arizona also has a strong connection to this chile industry.  For example, the Curry Chile Seed Company, based in Pearce, AZ, provides the seed for >90% of the total green chile acreage across the SW Chile Belt.
Chile peppers (Capsicum species) are among the first crops domesticated in the Western Hemisphere about 10,000 BCE (Perry et al., 2007).  The Capsicum genus became important to people and as result, five different Capsicum species that were independently domesticated in various regions of the Americas (Bosland &Votava, 2012).  Early domestication of chile peppers by indigenous peoples was commonly driven for use as medicinal plants.  Due to their flavor and heat characteristics, chile peppers are a populate food ingredient in many parts of the world, including Latin America, Africa, and Asia cuisines.  Chiles have been increasingly important to the U.S. and European food industries, particularly as these populations become more familiar with chile (Guzman and Bosland, 2017).
 
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.
 
The Capsicum annuum species is the most common group of chiles that we encounter and there are at least 14 very different pod types in this single species that includes: New Mexico (aka Anaheim), bell peppers, cayennes, jalapeños, paprika, serrano, pequin, pimiento, yellow wax, tomato, cherry, cascabel, ancho (mulato, pasilla), and guajillo (Guzman and Bosland, 2017).
Crop Phenology
Plants vary tremendously in their physiological behavior over the course of their life cycles.  As plants change physiologically and morphologically through their various stages of growth, water and nutritional requirements will change considerably as well.  Efficient management of a crop requires an understanding of the relationship between morphological and physiological changes that are taking place and the input requirements.  
 
Heat units (HUs) can be used as a management tool for more efficient timing of irrigation and nutrient inputs to a crop and also pest management strategies.  Plants will develop over a range of temperatures which is defined by the lower and upper temperature thresholds for growth (Figure 1).  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 units systems have largely replaced days after planting in crop phenology models because they take into account day-to-day fluctuations in temperature.  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 are 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 hiatus in blooming as the plant works to mature the chile fruit crop that has been developed.  
 
The first step in developing a phenological guideline for chiles would be to look for critical stages of growth in relation to HU accumulation.  Figure 2 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). 
 
Water and nutrient demands coincide with the fruiting cycle and efficient management of irrigation water and plant nutrients is enhanced by tracking crop development in the field.  The use of HUs (86/55 ^oF thresholds) can be applied since the thermal environment impacts the development of all crop systems, including chiles, (Figures 2 and 3).
 
 
Use of HUs to predict chile development is considered superior to using days after planting due to the simple fact that the crop responds to environmental conditions and not calendar days.  This approach, using phenological timelines or baselines, works best for irrigated conditions where crop vigor and environmental growth conditions are more consistent than in non-irrigated or dryland situations where irregularity in year-to-year rainfall patterns can alter growth and development patterns significantly.
 
 
Crop Phenology Relationship to Nutrient and Water Demand
 
Phenological guidelines can be used to identify or predict important stages of crop development that impact physiological requirements.  For example, a phenological guideline can help identify stages of growth in relation to crop water use (consumptive use) and nutrient uptake patterns. This information allows growers to improve the timing of water and nutrient inputs to improve production efficiency. For some crops or production situations HU based phenological guidelines can be used to project critical dates such as harvest or crop termination.  Many other applications related to crop management (e.g., pest management) can be derived from a better understanding of crop growth and development patterns.
 
ADDITIONAL NOTE:
 
Arizona Hosts the 2022 International Pepper Conference (IPC), 26-28 September 2022, Tucson and Pearce, Arizona.
 
Registration for the International Pepper Conference.  Registration and additional information can be found at https://extension.arizona.edu/ipc/
 
 Here’s a note from the conference Chair and Host, Mr. Ed Curry:
 
With the final countdown to the 25th biennial International Pepper Conference just days away, we want to encourage everyone who grows, processes, conducts research, educates about, or just enjoys chile peppers to get on board!  
 
The early bird pre-registration discount ends August 26th!
 
We are also excited to announce that for anyone interested in only the field day portion of the event (Sep. 27th), a stand-alone, one-day registration is available for $200 with walk up/ same day attendees welcome!
 
The conference will have an active schedule with many educational opportunities including:
 
•           Farm level breeding programs
•           Mechanical harvest technology
•           Pepper diseases and their management
•           Basic crop management science, heat units, fertility, and irrigation protocols – Dr. Jeff Silvertooth, University of Arizona
•           Breeding mechanical harvest type plants with Dr. Stephanie Walker, New Mexico State University
•           How to grow any type of PEPPER for mechanical harvest with Dr. Ben Villalon, Texas A&M Professor Emeritus
•           Disease prevention at a molecular level with Dr. Steve Hansen, New Mexico State University
•           Pepper flavor at the molecular level with Dr. Randy Hauptmann, BioGold LLC
•           Biopharmaceuticals at a molecular level with Dr. Bhimu Patel, Texas A&M
 
And the list goes on......
 
What we hope to encapsulate in our program is the integration of basic on-farm agriculture and advanced technologies to demonstrate the importance of both approaches in moving forward the multifaceted and beautiful world of 🌶PEPPER!
 
WE CORDIALLY INVITE ANY AND ALL PARTICIPANTS. WALK UP REGISTRATIONS WILL BE WELCOME! I AM EXCITED TO SEE YOU THERE!

YOUR HOST OF THE 2022 INTERNATIONAL PEPPER CONFERENCE,
ED CURRY

Figure 1.  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).

New Mexico - Type Chile Plant Development as A Function of Heat Units

Figure 2.  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.
 
Perry, L., Dickau, R., Zarrillo, S., Holst, I., Pearsall, D. M., Piperno, D. R., et al. 2007.  Starch fossils and the domestication and dispersal of chili peppers (Capsicum spp. L.) in the Americas. Science, 315, 986-988.
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.

 

Bindu Poudel-Ward, Martin Porchas Sr., Martin Porchas Jr., Neeraja Singh, Johan Murcia, and Rebecca Ramirez, and Jason Furr 

Yuma Agricultural Center, University of Arizona, Yuma, AZ

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Lettuce was seeded, then sprinkler-irrigated to germinate seed on Nov 15, 2022 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 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 Jan 5, 2023  at the 3-4 leaf stage to a 12-inch spacing. Treatment beds were separated by single nontreated beds. Treatments were applied 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
November (2022)	74°F	47°F	60°F	0.00
December (2022)	69°F	42°F	54°F	0.11
January	67°F	42°F	55°F	0.16
February	70°F	41°F	55°F	0.37
March	75°F	46°F	62°F	0.28

 
Sclerotia of Sclerotinia minor were produced in 0.25 pt glass flasks containing 15 to 20 sterilized 0.5 in. cubes of potato by seeding the potato tissue with mycelia of the fungus. After incubation for 4 to 6 wk at 68°F, mature sclerotia were separated from residual potato tissue by washing the contents of each flask in running tap water within a soil sieve. Sclerotia were air-dried at room temperature, then stored at 40°F until needed. Inoculum of Sclerotinia sclerotiorum was produced in 2 qt glass containers by seeding moist sterilized barley seeds with mycelia of the pathogen.  After 2 mo incubation at 68°F, abundant sclerotia were formed. The contents of each container were then removed, spread onto a clean surface and air-dried. The resultant mixture of sclerotia and infested barley seed was used as inoculum. Lettuce ‘Magosa’ was seeded and then sprinkler-irrigation was initiated to germinate seed in double rows 12 inches apart on beds with 42 inches between bed centers.  Plants were thinned Jan 6, 2020 at the 3-4 leaf stage to a 12-inch spacing. For plots infested with Sclerotinia minor, 0.13 oz (3.6 grams) of sclerotia were distributed evenly on the surface of each 25-ft-long plot between the rows of lettuce and incorporated into the top 1 inch of soil. For plots infested with Sclerotinia sclerotiorum, 0.5 pint of a dried mixture of sclerotia and infested barley grain was broadcast evenly over the surface of each 25-ft-long lettuce plot, again between the rows of lettuce on each bed, and incorporated into the top 1-inch of soil. Treatment beds were separated by single nontreated beds. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of a 25 ft length of bed, which contained two 25 ft rows of lettuce. Control plots received sclerotia but were not treated with any fungicide. As a point of reference, the original stand of lettuce was thinned to about 65 plants per plot.
   
For treatments first applied at seeding, sclerotia were introduced into plots before the first application of treatments. The first application for at seeding treatments was made on Nov 15, with an additional application on January 5, 2023. Some treatments had second application on  Jan 19. 2023 (See table). For treatments first applied after thinning, sclerotia were introduced into plots after thinning before the first application of these treatments, with additional applications as noted in the data sheets. An initial sprinkler irrigation supplied water for seed germination, with subsequent furrow irrigations for crop growth. The final severity of disease was determined at plant maturity by recording the number of dead and dying plants in each plot due to Sclerotinia minor or Sclerotinia sclerotiorum (March 15, 2023).  As a point of reference, the original stand of lettuce was thinned to about 65 plants per plot.
In nontreated plots, 4-5% of lettuce plants were dead or dying due to infection with Sclerotinia sclerotiorumand  about 15 %  due to S. minor, at the end of the trial.  Please refer to the data tables to compare treatments of interest, using the Least Significant Difference Value listed at the bottom of each table to determine statistically significant differences among treatments.  (UA-3 Experimental)+Silwett,  and Endura fb Merivon +Silwett were most effective against Sclerotinia sclerotiorum. UA-3 Experimental)+Silwett gave the best results against Sclerotinia minor as well (see table). Phytotoxicity was not observed in any of the treatments in this trial. 

Last fall, we established trials investigating the use of band-steam to control weeds and Fusarium wilt of lettuce in iceberg and romaine lettuce. Band-steam is where, prior to planting, steam is injected in narrow bands, centered on the seedline to raise soil temperatures to levels sufficient to kill weed seed and soilborne pathogens (>140 °F for > 20 minutes). After the soil cools (<1 day), the crop is planted into the strips of disinfested soil.

In the study, we utilized the prototype band-steam applicator (Fig. 1) described in a previous UA Veg IPM articles (Vol. 11 (13) to inject steam into the soil as beds are shaped. The steam applicator was configured to treat a 4” wide by 3” deep band of soil. Three rates of steam (Low, Standard, High) were applied by varying travel speed. The “Standard” rate was where steam was applied at rates needed to reach the target soil temperatures (>140 °F for > 20 minutes). Higher and lower applications rate were examined to ensure target temperatures were met/exceeded to get a better understanding of the efficacy of steam treatment, and to determine if higher travel speeds (less fuel consumption) could be used and still provide effective pest control.

Results showed that application of steam was highly effective at controlling weeds (nettleleaf goosefoot predominant species). At the Standard application rate, over 80% of the weeds were controlled. At High application rates, weed control approached 100%. What was particularly encouraging was that at the Low steam application rate where travel speeds were 60% faster than Standard, and target temperatures were not met, weed control was still very good – about 75%.

Steam treatment was also effective at controlling Fusarium wilt of lettuce. Disease incidence in iceberg and romaine lettuce were reduced by more than 50% as compared to the untreated control (Table 2). Crop plants were noticeably larger and more vigorous throughout the growing season in all steam treated plots (Fig. 2). At the Standard and High application rates of steam, this translated into significant yield increases in iceberg (>300%) and romaine (>90%) lettuce. Significant yield increases were also found at the Low application rate of steam – iceberg (>200%) and romaine (>60%).

The results are very promising, but it is important to note that steam treatment is not an end-all cure for Fusarium wilt disease. At the trial site, disease inoculum levels were considered moderate. However, when inoculum levels are very high, our trials have shown that a 4” wide by 3” band of soil is not effective at controlling the disease. We hypothesize that a wider and/or deeper band of treated soil is needed for effective control. This fall, we will be initiating trials to examine this. We will also be investigating the use of band steam to control pythium and nematodes in carrot. Trial results will be presented in future articles - so Stay Tuned.
As always, if you are interested in seeing the machine operate or would like to test the machine on your farm, please feel free to contact me.

Acknowledgements
This work is supported by the Arizona Specialty Crop Block Grant Program and the Arizona Iceberg Lettuce Research Council. We greatly appreciate their support. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

Fig. 1. Band-steam applicator principally comprising a 35 BHP steam generator mounted on a bed-shaper applicator sled.


Fig. 2. Iceberg lettuce planted in beds treated with steam (left) prior to planting and untreated (right).

As we continue to be impacted by the drought in Arizona with a 21% reduction in the Colorado River water allocation, we need to reconsider every option for water conservation in our agricultural operations. 
We know that weeds compete with our crops for water, nutrients, and space causing yield reductions. However, how much water are we loosing due to high weed infestations?
 
Some researchers have concluded that weeds use more water than various crops and consider them “water wasters”. Therefore, good weed control can contribute to raise available water for our crops. Transpiration of some of the most common annual weeds is approximately four times higher than crop plants. It has also been reported that weeds use up to three times the amount of water to produce a pound of dry matter. A study showed “common lambsquarters (Chenopodium album) requires 658 pounds of water to produce one pound of dry matter, common sunflower (Elianthus annus) requires 623 pounds, and common ragweed 912 pounds, compared with 349 pounds for corn and 557 pounds for wheat¹.” It has been reported that increase from 0 - 8 plants / row meter of Palmer amaranth (Amaranthus palmeri) densities in corn decreased soil water available and the water use efficiency (WUE) of corn.
 
Uncontrolled weed growth can add direct irrigation costs of more than $50/ha while even weed densities below economic thresholds can add ~$20/ ha in production costs depending upon the cropping system and water cost (Norris,1996).
Under stress condition such as we experience yields can be reduced more 50% just by moisture competition. Other factors that influence water loss are weed densities, transpiration rate, other weed characteristics like root system and depth. For example, perennial weeds with a well-established root system are more drought resistant because they can explore better the soil profile.
 
Some report that weeds can potentially cause 34 percent of crop loss worldwide. We have seen how weeds cut the water flow in irrigation ditches and cause more evaporative loss. We believe weed control is essential for water conservation purposes and further research is needed in this matter.
 
 
Reference:
1. https://www.researchgate.net/profile/Hussein-Abouziena-2/publication/278020092_Water_loss_by_weeds_A_review/links/5578c26608ae752158703bdc/Water-loss-by-weeds-A-review.pdf

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.

Leaf miners: Adult activity light in all areas, about average for this time of season