Jun 14, 2023Sanitation and Summer Whitefly Management (2023)To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
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).
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.
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.
Though sunflower is not a major crop in Arizona, it is one of the common ornamentals grown in home gardens. We have been witnessing some sunflowers in the area with the disease. It is also important to know about the diseases in sunflower as Arizona is home to large population of wild sunflowers.
Several species of the genus Rhizopus have been implicated in causing head rot, including R. arrhizus A. Fischer, R. stolonifer (Ehrenb.:Fr.) Vuill., and R. microsporus Tiegh. It has historically been considered to be of minor importance, however, it was documented as causing severe losses in Israel, and a recent survey of sunflower diseases in California found that Rhizopus head rot was the most common disease of sunflower. Under favorable conditions, it caused 100% losses in certain field. Infection is initiated in heads through wounds created by hail, birds, or insects.
Symptoms first become noticeable as dark spots on the back of ripening heads, followed by a watery soft rot that later turns brown. As disease progresses, heads dry prematurely, shrivel, and tissues appear to shred. Inside shredded tissues, coarse, thread-like mycelial strands are observed, followed by the appearance of small black dots (sporangia). Sporangia are filled with spores that are easily released and wind-blown to other plants. Symptoms on the flower side of heads include the appearance of mycelium, a grayish, fuzzy substance that is covered with sporangia (Fig 1-7)
Some type of mechanical injury on the head in combination with high temperatures and high relative humidity are required for infection and disease progress. Damage and economic losses are dependent upon time of the season that wounding and infection occurs. Infection rarely occurs before flowering, and greatest yield reductions result when infection occurs before seeds are properly filled. Infection in Israel has been primarily attributed to wounds from bird feeding. In the US High Plains, disease is initiated through head moth infestations and severe storms with hail.
Disease problems can be reduced by controlling the head moth at or before flowering, and by avoiding mechanical wounding after flowering. If you are growing sunflower commercially, it is also important to rogue or control volunteer and wild sunflowers before they produce seed; they may serve as a reservoir for insects and the Rhizopus.
Fig 1: Symptom of Rhizopus head rot on sunflower
Fig 2-7 Source: https://extensionpublications.unl.edu/assets/pdf/g1677.pdf
Please watch a demonstration of a spray assembly delivering herbicidal spray (blue dye) to spot spray targeted weeds. The device will be integrated with an imaging system for precision, automated / robotic weed control. Weed targets and crop plants are indicated on paper by green and yellow squares respectively. The same targeting pattern is used for simulated weeds (small plastic plants) and crop plants (white roses). Off target spray on paper is due to liquid splashing on a hard surface and is not observed on plastic weed targets. The travel speed is 2 mph and nozzle height - 5".
Click on the following demonstration link or the picture area:
Teff grass (Eragrostis tef) is originally from Ethiopia and has gained a lot of interest in Arizona. This crop is planted between vegetables and grows under different conditions and soil types. It is a fast-growing crop and can be harvested multiple times. According to the Teff Grass Crop Overview and Forage Production Guide from 2007-09 in California it was cut an average of 4 times yielding 6.89 tons/acre. The palatability to livestock is good and some report that its preferred over other traditional grass hays1.
There is also a need for good weed control in Teff grass to satisfy buyers.
One herbicide that was tested for postemergence broadleaf weed control and crop safety is Simplicity (pyroxulam). A 24(c) Special Local Need Registration was extended for this product. Also, another product that is successfully used in our area for broadleaf weed control is Clarity (dicamba).
Teff is grown during the summer between other crops that could be susceptible to residue of herbicides, and it is important that any herbicide that is used doesn’t have long-term soil activity.
We conducted a trial last summer in the Yuma Valley to evaluate the crop safety of pyroxulam, dicamba and other herbicides. Our results for pyroxulam were consistent with the injury observed in the visual ratings obtained by B.J. Hinds-Cook, D.W. Curtis, A.G. Hulting and C.A. Mallory-Smith with a 10% recorded2.
Also, efficacy for the control Purslane (Portulaca oleracea) was evaluated. The following chart shows data obtained.