Pest invasion likely across Southwest

New invasive pest species come not only from Mexican but also from adjoining state

New Mexico State University entomologists say a combination of a wet winter and spring and the encroachment of new and varied invasive insect pests from surrounding states and Mexico could cause problems this year for agricultural producers across the Southwest, including risks to New Mexico's prized alfalfa and chile crops.

Jan Pierce, NMSU Extension entomologist, warns that concerns over the introduction of new invasive pest species could also adversely affect fruit and vegetable crops.

"We try to intercept them before they get into the U.S., then before they get into New Mexico, but insects are often very good at migrating into new areas. We try to eradicate them when there are isolated pockets, but some insects will get well established...and we need to learn how to minimize damages from these new pest varieties," Pierce said.

New invasive pest species come not only from Mexican but also from adjoining states. For example, sugarcane aphids from South Texas will most likely infiltrate grain sorghum fields in New Mexico this year, and spotted-winged drosophila flies in Colorado could move south and plague the state's fruit industry.

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New Mexico Department of Agriculture state entomologist Carol Sutherland, who is also a NMSU Extension specialist, says introduction of these new pests can reduce yields as well as diminish product quality, affecting financial stability and potentially agricultural jobs across the region.

"Marketing problems can be compounded by the negative responses of other states or countries to the arrival and establishment of a new invasive pest," Sutherland said. "While diversification of crops can cushion some of the impacts of a new invasive pest, it may make crops affected by this pest less attractive or useful for crop rotation."

Alfalfa threat

Pierce says perhaps of greatest concern for New Mexico agriculture is the state's high quality alfalfa hay crop. Alfalfa has an impact of about $300 million in annual revenue for the state, making it New Mexico's number one crop.

Part of the problem is that it can be hard to differentiate between pest damage and disease damages. Alfalfa growers are sometimes surprised to find unexplained damage from the white fringed beetle.

Pierce explained that the larvae of this beetle, which causes the damage, cannot be treated, but adult populations can be reduced by treating them with an insecticide.

"Growers don't always recognize the damage because it looks like damage from diseases," Pierce explained. "You need to look for thinning spots, then dig up plants and check the roots to see if there are any holes."

New Mexico's grape and wine industries should be on the lookout for winged drosophila flies as well as a very large leafhopper — the glassy-winged sharpshooter — a potential vector of Pierce's disease that can kill grape vines.

Another pest to watch is the Bagrada bug. While the bug migrated from Mexico into some southern areas of the state, areas in the state's interior could be at risk as the pest migrates north. The pest is attracted to cruciferous vegetables, canola, potatoes, corn, sorghum, cotton and some legumes.

In New Mexico, the Bagrada bug prefers Chinese greens, arugula and mustards as well as various weeds, including London rocket, wild mustards and pepperweed.

This bug is known to leave scorched leaves and blind terminals. They hide at the base of the plant and on soil cracks or crevices.

"It is best to check the plants during mid-morning when temperatures are higher and the insects are more active," Pierce advises.

Long list of invasive pests

The list of invasive pests on New Mexico's doorstep continues to grow. Tree-killing emerald ash borers were confirmed in Colorado, Arkansas and Louisiana in 2013, 2014 and 2015, respectively. Japanese beetles are established in parts of Colorado and the eastern parts of Oklahoma and Kansas, where significant amounts of nursery stock are sourced for New Mexico's nursery industry.

Exotic fruit flies from Mexico, Central America or elsewhere pose a particular threat since their larvae can be difficult to detect in the large amounts of imported fresh produce entering the U.S.; these invasive pests represent a threat not to just fruit growers (apple, cherry, peach) but also to the chile industry since chile pods are botanically fruits.

Pierce said the Southwest region of the United States also needs to be on the lookout for the brown marmorated stink bug, which is now common in much of the eastern U.S. It has previously been found in Texas and once in New Mexico.

Cropland is not the only economic issue. European honey bees have been plagued by invasive pests including honeybee tracheal mites, varroa mites and pathogens they transmit, and most recently, small hive beetles.

Pierce urges growers to talk to their county agents and take any insects or damaged plants to them to be examined if they see unusual problems.

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