Growing Chiles in New Mexico
Guide H-230Paul W. Bosland, Professor of Agronomy and Horticulture
Alton L. Bailey, Extension Vegetable Specialist, Emeritus
Donald J. Cotter, Professor of Vegetable Production, Emeritus
College of Agriculture, Consumer and Environmental Sciences New Mexico State UniversityThis Publication is scheduled to be updated and reissued 3/04.
The Chile Plant
Chiles have been grown in New Mexico for at least four centuries. However, only in the past two decades has chile become an important cash crop for farmers. Since 1970, chile acreage has increased more than four-fold, and many growers have begun to produce chile for the first time. In 1990, more than 28,000 acres of chile were planted in New Mexico. Most chiles are grown under contract and sold to processors. Processors usually prefer mildly pungent chiles. Chiles for local sales are a relatively small part of total commercial chile acreage, but chile is a good cash crop for some growers. Dried red chiles can be strung on ristras for ornamental and culinary use.
Varieties and Cultivars
Many chile varieties are grown in New Mexico, such as bell, New Mexican, jalapeño, cayenne, ancho, pasilla, mirasol, and de arbol. New Mexican-type cultivars include 'New Mexico 6-4', 'NuMex Big Jim', 'Sandia', 'NuMex R Naky', 'NuMex Conquistador', 'NuMex Sweet', and 'NuMex Joe E. Parker'. Each cultivar has specific requirements for good growth. When choosing chile cultivars for New Mexico, consider yield, use, disease resistance, adaptability, and market acceptance. A good source of information is the Chile Pepper Institute at www.nmsu.edu/~hotchile
Preparing the Land
Rotate chile with wheat, barley, oats, corn, alfalfa, and cotton to help prevent disease and to provide productive chile crops. Do not plant chile in the same field more than once every 3 to 4 years.
A deep, well-drained, medium-textured sandy loam (or loam soil) is best for producing chiles. Good yields often result from planting chiles in a place that contained a flood-irrigated crop the previous year. Laser level the field at a grade of 0.01 to 0.03% in one or both directions. This drains the field of extra water, reducing the risk of root diseases.
Preparing soil involves plowing, deep chiselling, discing, smoothing, and listing. Form listed beds by scalping the top of the ridge with a drag harrow. Irrigate the field 5 to 7 weeks before planting. Plant chile seed before the soil dries.
Convert two normal-width beds into one wide planting bed (cantaloupe bed) with a bed-shaper. Plant seed on each side of the bed, about 4 to 6 inches from the water furrow.
In New Mexico, nutrients normally used on chiles are nitrogen and phosphorus. A soil test determines nitrogen, phosphorus, and micronutrient needs. The Soil, Water and Air Testing Laboratory at New Mexico State University can determine nutrient needs, pH, salt E.C., and sodium.
Broadcast the first nitrogen application and all the phosphorus before discing or listing. Band nutrients either when seed is planted or after seedlings have emerged. Phosphorus helps young seedlings grow, especially when soil warms in spring. Phosphorus is not needed if levels of soil phosphorus are between medium and medium-low, based on the New Mexico State University analysis system (Guide A-122, Soil Test Interpretation, Cooperative Extension Service, New Mexico State University). Add 50 to 100 lb of P2O5 per acre before discing if levels are lower. Alternatively, band phosphorus (30 lb of P2O5 per acre), 3 to 4 inches below the seed.
Preplant nitrogen also generates vigorous seedling growth, which ensures a well-branched plant by the first fruit set. Preplant nitrogen is not needed if a soil test shows the soil has 20 ppm nitrate or more. Broadcast 20 to 30 lb of actual nitrogen per acre before discing if nitrogen is needed. Otherwise, band nitrogen (2 to 5 lb per acre) 3 to 4 inches below the seed.
Apply a steady supply of nitrogen to the plant during fruit set to produce greater yields. New Mexico growers often use 150 lb of urea per acre when plants are thinned. While plants develop first fruits, analyze plant tissue samples to keep nitrate concentrations in the plant stem and petiole between 7,000 and 8,000 ppm.
Post-emergence nitrogen fertilization depends partly on whether the crop will be picked at the mature green stage or if it will be picked at the mature red stage. Normally, a mature green chile crop requires more nitrogen, particularly when second-harvest fruits develop. Apply a sidedress of 20 to 30 lb of nitrogen per acre in mid-June, when primary and secondary floral buds are evident and plants are 8 to 10 inches tall, and again in early July when many first-set fruits develop. Apply fertilizer in a continuous band, 4 inches to the side of the bed, 2 to 3 inches below the surface. Liquid fertilizer solutions can be added to irrigation water.
High-yielding or early-setting crops may benefit from a third nitrogen application. However, too much nitrogen can over-stimulate growth, producing large plants with few early fruits. During high rainfall and humidity, extra nitrogen delays maturity, results in succulent late-maturing fruits, and increases the risk of serious plant or pod rots.
Chile is a warm-season crop that requires a long, frost-free season to produce good-quality, high yields. Chiles do not thrive when temperatures are between 40°F and 60°F, and can die from a light frost. Plant between March 1 and April 1 for red and early green crops in southern New Mexico. Plant 30 days to 6 weeks later in central and northern New Mexico areas. The early green crop will be ready for harvest about 120 days after planting. The red crop will take about 165 days. Areas with a shorter growing season may have little or no red chiles for harvest.
In persistently cold weather, delay planting because seedling growth is slow in cold soils. Slow growth can prolong seedling exposure to insects, diseases, salt, or soil crusting, which can all kill seedlings. Transplant seedlings during April and stagger plantings for green harvest in late August and in September in southern New Mexico. This approach assures a regular harvest.
Plant high-quality seed. Two to three pounds of seed per acre produces a good stand. Some growers plant 5 to 8 pounds per acre because extra seed compensates for plant losses from curly top virus. Growers also plant to a stand by clumping 3 to 5 seeds every 6 to 10 inches.
Center the seed row when planting in pre-irrigated soil. Use a harrow to loosen the soil and plant seed 3/4 to 1 inch deep. Cover the row with a cap (a firm, protective soil layer, 3 to 4 inches high) to reduce water evaporation. Remove the cap with a dragging harrow when seedlings emerge (the crook stage). Carefully adjust soil-removal equipment so a loose, 1/4-inch layer of soil covers the seedlings after dragging. This avoids seedling damage and encourages rapid seedling emergence.
Plant either in the center or on the edge of a shaped bed, depending on salt content. Chile seedlings are susceptible to salt until they are 2 to 3 inches tall and growing rapidly. If soil has high residual salt, or irrigation water is salty, plant to one side of the bed to reduce salt concentration near seedlings. When planting on the side, move soil from the adjacent bed during cultivation. Continue to move soil until the plant row is eventually centered and on a high ridge.
Plant in dry soil on each edge of wide, cantaloupe bed furrows that are 60 inches or wider. Water in the furrow wets both rows, while salt accumulates in the center of the bed, away from both seeded rows.
Research shows pre-germinated seed, planted by fluid drilling techniques, emerges 3 to 4 days sooner than dry seed, but fluid drilling requires special planting equipment.
Row Spacing and Plant Population
The most common row width is 36 to 40 inches. Growers often space them to conform to requirements of other farm-rotation, row crops. Narrow row spacing, 32 inches, can result in higher yields, particularly for the second green harvest or the late red crop.
Thin the plants when they are actively growing, about 2 to 4 inches tall, and have two to four true leaves. Delay thinning to reduce chances of natural damage that may kill plants, such as curly top virus, damping-off, and salt injury. A good stand includes single plants, or clumps of no more than three plants, uniformly spaced 10 to 12 inches in the row of a 40-inch bed for a plant population of 13,000 to 15,000 plants per acre.
Transplanting chile seedlings was common before 1940. Today, most of the commercial chile acreage in New Mexico is directly seeded. Transplants are being tried again to promote earliness, allow for later-than-normal plantings, and to reduce seed cost.
Transplanting has some advantages. It guarantees a well-distributed stand of plants, reduces thinning costs, and requires less cultivation and irrigation. A crop can usually be established with one irrigation, compared to as many as three irrigations for directly seeded stands. Such economies help offset transplant and field setting costs.
Transplants are shorter than directly-seeded plants and have more branches. This can be detrimental when long fruits touch the soil, increasing the possibility of pod rot. Anticipated benefits of earliness and higher yields are not consistent, so growers should consider other factors (seed amount, thinning costs, water amount, and late planting opportunities) to decide whether to transplant.
Transplant 5- to 6-week-old plants that are 6 to 8 inches tall; space them 12 inches apart in the row. Retain as many roots as possible before lifting the transplant. Apply a high-phosphorus starter solution to the soil during transplanting to aid in establishment.
Shallow cultivation controls weeds and increases soil aeration. However, deep cultivation, as done on cotton crops, can result in a higher incidence of Phytophthora root rot. Apply herbicides to control weeds, but consult your county agent or NMSU Extension weed specialist before application.
Fruit Set and Development
Chile plants usually start flowering in mid-June in southern New Mexico, with a single flower at the first branching node. Plants flower later in northern areas. Flower number doubles with each extra node. Fruits from early flowers are usually large and have greater red color content at maturity.
Fruits do not set when mean temperatures are below 60°F or above 90°F. However, flowers drop when night temperatures are above 75°F. Fruit set may be stalled if temperatures rise above 90°F after several flowers have set and fruits are developing. This causes a split in the fruit setting continuum, and is called a split-set. Early yield is determined by fruits developing before the onset of hot weather. Delay in fruit set can reduce yields. It also causes fruit to set high on the plant, which makes plants more prone to wind damage as they mature.
Chiles usually grow to full pod length in 4 to 5 weeks; pod weight increases as fruit walls thicken. Fruit normally reaches the mature green stage 35 to 50 days after the plants flower.
Chile is a shallow-rooted crop, and needs 4 to 5 acre-feet of water between planting and harvest. Up to 70% of the water absorbed by full-canopy chiles is removed from the top 1 foot of soil. Optimum irrigation time can be determined by testing soil moisture in the root zone by touch, with moisture sensors, or by computer predictions.
Irrigation varies with amount of plant foliage, wind, sunlight, temperature fluctuation, and relative humidity. Watch forming plant leaves to estimate how often to irrigate. During hot, drying conditions, expect swiftly growing plants to wilt late in the afternoon, even the first day after irrigation. Wilting signs begin to appear earlier in the day as soil dries. Irrigate when plants wilt in early afternoon.
Irrigate less often when plants are small. It may not be necessary to irrigate for 3 weeks or more after emergence because plant roots are growing into moist soil. Apply water on a 5- to 7-day schedule between late June and July, before summer rains begin. After the rains begin, extend the interval to 7 days or more, depending on rainfall amount. Do not water when the risk of summer rains is high. Decrease irrigation frequency at the end of the season to promote ripening and to improve fruit color. Phytophthora root rot disease can develop from water standing in the field for more than 12 hours, so a means of draining the field is helpful.
Pest and Disease Control
Flea beetles, thrips, leafhoppers, and aphids can infest seedlings that were planted early, and reduce stands. Plants can die directly from insect injury or indirectly from viral diseases. A systemic insecticide applied to the soil during planting can reduce insect damage.
The Food and Drug Administration has increased restrictions of chemical residues in food products. Read the label before using any pesticide. Do not use any chemical, whether it is a herbicide, insecticide, nematocide, or fungicide, if it is not labelled for chiles. Consult the county agent or a New Mexico State University specialist before using the chemical if there is any doubt.
Root-knot nematodes can cause serious yield losses. The only nematode known to damage chiles in New Mexico is the southern root-knot nematode, Meloidogyne incognita. Take a soil sample as described in Extension publication 400 W-9, How to Take a Nematode Sample, if such a problem is suspected. The samples can be processed at the New Mexico Department of Agriculture. Again, the county agent or a New Mexico State University specialist can assist with control measures.
Common diseases that infect chile in New Mexico include Phytophthora root rot, Verticillium wilt, Rhizoctonia root rot, various viruses, and bacterial leaf spot. Two good resource publications on chile diseases are Identifying Chile Diseases, Extension Circular 511, and Chile Disease Control, Extension Circular 400 W-12.
Chile root rot disease, caused by the water mold Phytophthora capsici, is a major disease in New Mexico. Often called chile wilt, it differs from vascular wilts caused by Verticillium dahliae and Fusarium oxysporum. Large plants wilt and die, leaving brown stalks and leaves, and small, poor-quality fruits. The disease is most common in overwatered areas, such as low spots, heavy soils, lower ends (tails) of sloping fields or upper ends (heads) of long fields. Drain the field quickly to avoid infection.
To decrease overwatering, either apply water to alternate furrows or lengthen the time interval between irrigations. Remember reducing irrigation too much can stress plants for water, reducing yield. Drip irrigation is another way to reduce overwatering, and can also be used to apply fertilizers in a controlled way.
No approved chemical control for Phytophthora root rot exists. However, one cultural-control measure is cultivating so plants are grown on a high ridge after the last cultivation (Garcia, 1908). Limit row length to roughly 600 feet when planting on prone sites, which avoids overwatering soil at the upper end.
Another potential problem is Verticillium wilt disease, caused by a soil-borne fungus, Verticillium dahliae. This is a serious problem in some New Mexico fields. Crop rotation with a small-grain crop reduces the risk.
Virus diseases can also be a problem. Curly top virus, tomato spotted wilt virus, alfalfa mosaic virus, and pepper mottle virus all occur in New Mexico (Muhyi and Bosland, 1989). Aphids and leafhoppers are carriers of the viruses. Remove all Jimson weed, Datura stramonium L., within 1 mile of the field to help control pepper mottle virus. Avoid fields close to alfalfa to reduce alfalfa mosaic virus infection.
At least two fungi cause pod rots, which can be serious in rainy and humid seasons. The disease is even more likely to occur when plants are large and lush, and when foliage from other rows overlaps. Although fungicides provide some control, use methods that avoid over-stimulation of growth. Use defoliants, which control pod rot, late in the season to help accelerate maturity and dry plants which will control pod rot.
Blossom-end rot is a physiological disorder that appears as a dry, leathery, elongated, brown-to-black spot on the lower half of the developing fruit. Blemishes range from 1/4-inch spots to 2- to 3-inch-long elongated spots. Pods affected with blossom-end rot usually ripen prematurely. The disease appears when plants with rapidly developing fruit become stressed for water, and sufficient calcium cannot be transported to ripening pods. Irrigate when necessary during rapid pod development to control the disease.
Most growers harvest chile by hand. An ideal mature green pod of the New Mexican type that will be used for processing or fresh market feels firm when squeezed and is flat (has two cells), smooth, thick-fleshed, bluntly pointed, and about 6 inches long. A good harvest of green, destemmed fruit ranges from 7 to 10 tons per acre. Allow a few pods in the field to begin turning red, which is called the pinto stage, before the first harvest. This will increase the overall green chile yield. An ideal red pod is large (to facilitate harvesting), disease- and blemish-free, and high in red color content. Dry red yields range from 3,000 to 6,000 lb per acre in southern New Mexico.
Early planted chiles will make one early-August, green harvest, and the field can then mature for dry red harvest after frost. Red yields after a green harvest range from 65 to 100% of a full red crop. When red fruits are harvested from fields from which green fruits were previously harvested, red color is often lower. Alternatively, green chiles can be harvested a second time about 4 or 5 weeks after the first harvest. After the second harvest, if the season is favorable, a third set of fruits will develop and mature before frost. However, fruits are usually small and poorly colored, and may not be worth harvesting. If planting is delayed to schedule regular green harvests, red fruit quality and yield will vary according to time remaining for fruit growth, and daily heat amount between green harvest time and frost.
Although red fruit shape and size are less important for dry products, they need at least 160 ASTA (American Spice Trade Association) color units. If harvest is too early, some pods will be immature, and maximum color will not have developed.
The ideal harvest time is early October, when most pods are mature, and a frost has not yet reduced chile quality. If a harsh freeze occurs when red pods are succulent, pod cells rupture, causing sap leakage inside the pod. This leakage causes mold to develop, and reduces quality and yield.
Defoliants or desiccants, such as sodium chlorate, are often used to both accelerate fruit drying during wet weather and aid in harvesting. Ethephon® as a ripening enhancer may defoliate, as well as hasten, maturity. This chemical will also increase color of red chiles that are harvested before frosts.
Table 1. New Mexico seed companies that carry chile seed.
- Enchanted Seeds
P.O. Box 6087
Las Cruces, NM 88006
- Plants of the Southwest
1812 Second St.
Santa Fe, NM 87501
- Solar Dry Chile Products
P.O. Box 310
Salem, NM 87941
- Hatch Chile Express
P.O. Box 350
Hatch, NM 87941
- New Mexico Crop Improvement Association
New Mexico State University
Las Cruces, NM 88003-8003
Garcia, F. 1908. Chile Culture. New Mexico College of Agriculture and Mechanic Arts. Bulletin No. 67. 32 pp.
Muhyi, R. I. and P. W. Bosland. 1989. A survey identifying pepper viruses occurring in southern New Mexico. HortScience 24:93.
New Mexico State University is an equal opportunity/affirmative action employer and educator. NMSU and the U.S. Department of Agriculture cooperating.Reprinted March 1999
Electronic Distribution March 1999