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A Faster Way to Tell Look-alike Leafminer Flies Apart

By Luis Pons
July 30, 2002

Agricultural Research Service scientists have developed a new high-tech method for telling apart two species of leafminer insects, one of which has caused extensive crop damage around the world but is not known to be in the United States.

The test developed by ARS molecular biologist Sonja Scheffer combines two procedures--called polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP)--to differentiate between Liriomyza huidobrensis and L. langei, two species of leafmining flies so similar that scientists, until recently, believed they comprised one species.

Telling apart species of leafminers and other insects is greatly important to people such as quarantine officers, pest-management experts and researchers who work together to keep potentially damaging insects from entering the United States.

Leafminers affect many vegetable and flower crops, including peas, beans, melons, onions, tomatoes, potatoes, celery, garlic, lettuce, chrysanthemums and carnations. Their larvae tunnel inside leaves and other plant parts as they feed, leaving winding trails visible though the leaf surface. During outbreaks, they can cause substantial economic losses.

Scheffer's new PCR-RFLP analysis can be used with adult, larval or pupal specimens of leafminers. The test can be performed by anyone with access to a laboratory and the proper equipment. The entire procedure can be done in one day, compared to several days and additional expenses involved in another testing method called DNA sequencing.

Before developing the new detection method, Scheffer and biological sciences technician Matthew Lewis, based at the ARS Systematic Entomology Laboratory in Beltsville, Md., used DNA sequence data from leafminer genes to show that the two leafminer species existed. DNA data also showed that the invasive leafminers causing extensive crop damage around the world are L. huidobrensis, not L. langei. Currently, L. huidobrensis is not known to be present in the United States.

Read more about this finding in the July issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.