Southwestern Chile Production
Chile (Capsicum annuum) production is an important aspect of vegetable crop production systems in the desert Southwest.  In many respects, chiles are a trademark feature of crop production in the desert Southwest.  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 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 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 (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 unit 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 generally 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.  Accordingly, water stress in an irrigation system will alter phenological plant development and usually accelerate crop maturity and create an earlier crop and increase fruit abortion or cause smaller fruit development.
 
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.

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).




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.

Frost and freeze damage affect countless fruit and vegetable growers leading to yield losses and occasionally the loss of the entire crop. Frost damage occurs when the temperature briefly dips below freezing (32°F).With a frost, the water within plant tissue may or may not actually freeze, depending on other conditions. A frost becomes a freeze event when ice forms within and between the cell walls of plant tissue. When this occurs, water expands and can burst cell walls. Symptoms of frost damage on vegetables include brown or blackening of plant tissues, dropping of leaves and flowers, translucent limp leaves, and cracking of the fruit. Symptoms are usually vegetable specific and vary depending on the hardiness of the crop and lowest temperature reached. A lot of times frost injury is followed by secondary infection by bacteria or opportunist fungi confusing with plant disease.

Most susceptible to frost and freezing injury: Asparagus, snap beans, Cucumbers, eggplant, lemons, lettuce, limes, okra, peppers, sweet potato

Moderately susceptible to frost and freezing injury: Broccoli, Carrots, Cauliflower, Celery, Grapefruit, Grapes, Oranges, Parsley, Radish, Spinach, Squash

Least susceptible to frost and freezing injury: Brussels sprouts, Cabbage, Dates, Kale, Kohlrabi, Parsnips, Turnips, Beets

More information:

https://www.extension.iastate.edu

https://www.farmprogress.com

Over the last month, we’ve been developing a prototype wide bed steam applicator for injecting steam at shallow depths to kill weed seed prior to planting. The device principally comprises a 65 BHP steam generator mounted on a trailer and an elongated bed shaper (Fig. 1). The apparatus applies steam via shank injection and from ports on top of the bed shaper. The goal is to raise soil temperature to >140 °F for > 20 minutes, levels known to kill weed seed (Baker & Roistacher, 1957). Development is still in progress but results of preliminary tests are encouraging as soil surface temperatures were relatively uniform and exceeded 160 °F (Fig. 2). Experiments with baby leaf spinach crops will be conducted in the next couple of weeks. Stay tuned for trial results and reports on weed control efficacy and labor savings. 
References
Baker, K. F., and C. N. Roistacher. 1957. The U.C. system for producing healthy container grown plants. Calif. Agric. Exper. Sta. Ext. Serv. Manual 23.
Acknowledgements
This work funded in part by the Arizona Specialty Crop Block Grant Program. 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 USDA or the Arizona Department of Agriculture.

Fig. 1. Wide bed steam applicator principally comprising a 65 BHP steam
generator mounted on a trailer and a bed shaper applicator sled.


Fig. 2. Video of wide bed steam applicator. Soil surface temperature is presented
using an infrared thermometer gun.

The IPM team frequently receives questions from our friend PCAs in Yuma regarding possible injury with herbicide combinations. A recent inquiry was about the addition of Prowl (pendimethalin) to Prefar herbicide preplant.
We found in our archives an evaluation that was done in 2002 by Barry Tickes from Arizona Cooperative Extension that addressing this question. The evaluation was located on 8^th Street and the Levee in Yuma CO and included the following treatments: Dacthal at 10 and 12lb, Prefar at 6qt alone and with the addition of 0.5pt Prowl. All treatments were applied in 20 gallon/A spray volume as a 50% band on 42-inch beds. The plot size for this experiment was 600 ft. x 8 beds. Immediate incorporation was done with sprinkler irrigation. The results reported are in the following table:

As can be seen the addition of 0.5pt of pendimethalin to 6qt of bensulide produced 20% stunting in this case. 

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

Corn earworm: CEW moth counts remain at low levels in all areas, well below average for this time of year.

Beet armyworm: Trap increased areawide; above average compared to previous years.

Cabbage looper:  Cabbage looper counts decreased in all areas; below average for this time of season.

Diamondback moth: DBM moth counts decreased in most areas. About average for this time of the year.

Whitefly: Adult movement beginning at low levels, average for early spring.

Thrips: Thrips adult counts reached their peak for the season. Above average compared with previous years.

Aphids:  Aphid movement decreased in all areas; below average for late-March.

Leafminers: Adults remain low in most locations, below average for March.