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Welcome rains bring unwanted cutworms to Southeast New Mexico

Cutworms could threaten New Mexico alfalfa. Conditions may favor cutworm survival. Alfalfa is New Mexico’s top crop.

While New Mexico remains at the top of the list of states with the most severe drought conditions in the nation, recent rain showers have been a welcome relief to many areas, including water-thirsty southeastern New Mexico.

But as growers begin their fourth cutting of alfalfa in parts of the hay-rich region, a New Mexico State University research center entomologist is warning producers to be on the watch for what could be an outbreak of variegated cutworms in and around Eddy County, a concern prompted by a similar outbreak of cutworms three years ago that wiped out much of the alfalfa crop south of Carlsbad.

"I don't want to sound the alarm because early reports of cutworms may not develop into a major problem as it did a few years back. But we are getting reports of cutworms in some fields, and since the rains last week, conditions are similar to what they were when we had the major outbreak a few years back," said Dr. Jane Pierce, entomologist at the New Mexico State University Agricultural Science Center in Artesia.

Pierce has worked the southeast region of New Mexico over the last 17 years and says this is only the second time she has seen significant numbers of cutworms during the heat of summer.

"Generally this time of year the heat and low humidity takes care of the problem for us. But like the last and only time I am aware of a cutworm problem in July was when rains, humidity and cooler temperatures were providing an opportunity for eggs to hatch, and that could be the case again this year if those weather conditions were to continue," she warned.

Pierce says late last week nearly a dozen cutworms were collected per night in pheromone traps at the research center's farm and were reported in other fields as well.

"Now is the time to survey alfalfa fields. If caught early enough they can be treated, but if unattended they can quickly do a great deal of damage," she said.

NMSU extension agronomist Mark Marsalis agrees.

"If you are scouting your fields and are finding two to three larvae per square foot you have reached the threshold of justifying treatment versus potential losses," Marsalis warns. "It is estimated that a single larvae can cause about a 2 percent loss on an acre of good alfalfa, so when you hit that threshold it's time to begin treatment."

High quality alfalfa remains in demand in southeastern parts of the state where there are a large number of dairy operations. Prices still hover around $275 a ton in and around Eddy County, where cutworms have been discovered in recent days.

"So at two to three larvae per square foot, growers are looking at over $10 per acre impact, so damages can add up quickly if the problem is not treated," Marsalis added.

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Alfalfa is New Mexico's leading agricultural crop and is recognized far and wide for its high quality. It also is credited with fueling the state's respected dairy industry. In a USDA report (2007) New Mexico was ranked sixth in the nation for dairy product production, seventh in milk production, and eighth in cheese production. These rankings were driven by consistent and strong production of alfalfa crops. While the state is known for its successful onion and chili pepper crops, alfalfa remains at the top of the list most years in both production tonnage and revenue.

Marsalis says alfalfa is generally New Mexico's largest cash crop sharing the spotlight only with the state's highly successful pecan crop.

"Most years alfalfa remains king of New Mexico's crop production, but it does compete with commercial pecan operations in the southeastern region of the state," he said.

History of Alfalfa in New Mexico

Introduced first by the Spanish in the 1500s, alfalfa has long played an important role in New Mexico's agriculture industry. By 1967, alfalfa had become the most important cash crop in the state and accelerated in value to a peak of nearly $150 million in 1984.

Agricultural statistics showed that by 1920 there were 128,000 acres of alfalfa in New Mexico. Acreage then declined to 80,000 in 1935 and, thereafter, increased to a maximum of 270,000 acres in 1981. Total production ranged from a low of approximately 200,000 tons in 1935 to a high of 1.33 million tons in 1984.

In 1996, New Mexico farmers produced nearly 1.38 million tons of alfalfa on 255,000 acres. The average alfalfa hay yield for the state in 1996 was 5.40 tons per acre compared to 4.30 tons in 1980 (New Mexico Agricultural Statistics). Using a season average price of $126.00 per ton, the value of the 1996 New Mexico alfalfa crop was approximately $173.5 million.

Last year (2012), USDA reports 285,000 acres of all hay varieties (200,000 of alfalfa) was produced yielding 4.75 tons per acre (5.5 tons per acre for alfalfa). In all, 1.355 million tons of hay was produced of which 1.1 million tons were alfalfa varieties.

Because of irrigation and climate, New Mexico generally produces between three to eight cuttings of alfalfa, with six cuttings generally accepted as the best to produce high quality alfalfa for dairy use. Currently in the southeast region growers are cutting their third alfalfa crop and in Eddy County a few are reporting they have started their fourth cutting of the year.

Pest management program

Over 30 percent of New Mexico’s alfalfa is exported to out-of-state buyers. New Mexico producers consistently monitor insects including the blister beetle. With New Mexico State University's (NMSU) outstanding pest management program, coupled with effective, environmentally safe controls, producers continue to reduce unwanted insect population in New Mexico alfalfa.

Through the work of NMSU and its extension service, ongoing research into alfalfa has produced outstanding varieties and methods of production that under the right conditions can and does provide an excellent and nationally recognized hay crop.

Most years, free from the constant worry of unkindly rain, hay producers can control irrigation, cutting and baling to meet the exact specification for premium hay. The relatively low humidity is ideal for perfect curing of windrowed hay, with an absolute minimum of quality and nutrient loss.

In addition, part of the essence of New Mexico's hay quality is that most hay is baled at night – a technique not as common in less arid regions of the country. When the humidity begins to rise during the night, New Mexico farmers spend countless night-time hours monitoring the humidity and making many moonlit trips to check fields, waiting for the perfect baling conditions.

Doña Ana County ranked second in cash receipts, with crop production (first in the state) representing 49.9 percent of its total. Several eastern counties—Chaves, Roosevelt, Union, Lea, and Eddy—followed Curry and Doña Ana counties in cash receipts.

Cutworm scouting is best defense

Pierce and Marsalis agree that scouting fields is necessary to control losses caused by cutworms.  They recommend scouting in the early morning or late evening. During warmer periods of the day cutworms generally can only be found in the soil, often at depths of an inch or more.

"It's also wise to control weeds along the border of alfalfa fields and anywhere in near proximity. Often eggs will hatch and larvae will survive in weeded areas, so maintaining a weed free environment near forage crops can help control potential damage caused by harmful cutworm populations," Pierce said.

Pierce also recommends staggering hay cuttings.

"We have discovered that fresh cut alfalfa fields can have both a positive and negative impact on cutworm populations. On one hand, cut fields allow the soil to heat up and this helps reduce the number of eggs that hatch. But it also causes the loss of beneficial predatory insects that feed on small larvae, so staggering your cuttings from field to field may prove to be an effective counter measure," she added.

Typically, female moths lay hundreds of eggs, often in small clusters. They deposit them on low-growing plants such as weeds. Migrating moths lay eggs on the soil as well and the larvae hatch to feed on various types of plants. Young larvae feed on the foliage or small roots of weeds and crops until they reach about a half-inch in length.

"When scouting for cutworm in fields the smaller larvae are of the most concern. These small larvae are not only treatable, but once they reach a certain growth stage, nature is going to take care of the problem for us. Damage is caused primarily from the smaller larvae and this is where we need to concentrate our control," Marsalis advises.

In addition to treating fields, another positive strategy is to make certain not to add to the problem by sustaining conditions that contribute to more eggs hatching. For example, growers should avoid irrigating alfalfa fields soon after beneficial rains have fallen. By keeping the soil moist and cool, conditions are better for cutworm development.


Also of interest:

RR alfalfa’s advantages far outweigh disadvantages

Alfalfa Pest Management/Selecting Right Variety

Start scouting alfalfa soon for insect activity

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