March 31, 2022

(Cover photo: Biological Scientist Don Vacek placing bacterial samples on agar plates collected at PPQ’s Mexican Fruit Fly Rearing Facility in Texas. USDA photo by Bryce Blackman.)

Working Tirelessly to Develop Pest Detection and Management Methods 

By April Dawson

USDA’s Plant Protection and Quarantine (PPQ) program continues its Science and Technology laboratory article series by highlighting the Insect Management and Molecular Diagnostics Laboratory (IMMDL), formerly called the Mission and Phoenix labs. The IMMDL is comprised of two units, one in Edinburg, TX, and one in Phoenix, AZ. This article focuses on the Texas lab, which supports PPQ’s programs by developing pest detection and management methods, mitigation strategies, molecular diagnostic tools for insects and other invertebrate pests, and Asian citrus psyllid and Mexican fruit fly response activities. Next month we’ll cover the Phoenix lab.

“Our team works tirelessly to develop methods at IMMDL,” said Matt Ciomperlik, the lab's Director. “That work includes cutting-edge molecular approaches to study nucleic acids such as High Throughput Sequencing, real-time PCR, isothermal amplification, and microfluidic genotyping. These have been used to complete confirmatory pest identifications, track high-risk pathways of invasive species, and study insect genomes for new molecular markers.”

IMMDL is at the forefront of research to develop methods to confirm the identity and origin of exotic fruit flies trapped during surveillance operations or at U.S. ports of entry. Fruit flies such as the Mediterranean fruit fly, Oriental fruit fly, and Mexican fruit fly pose a serious threat to the production and safe trade of U.S. specialty crops.

PPQ also uses IMMDL-developed methods to support the production of beneficial insects—like sterile Mexican fruit flies—by detecting disease-causing microbes in rearing populations. “The IMMDL developed molecular methods to identify bacteria in PPQ’s Mexican Fruit Fly Rearing Facility,” said Biological Scientist Roxanne Farris. “PPQ rears these flies for our sterile release program in Texas. By releasing millions of sterile flies into an area, we reduce the chance that a wild Mexican fruit fly will produce offspring. Bacterial pathogens can significantly reduce insect production at a rearing facility, which in turn can negatively impact the control method.”

By accurately identifying the bacteria associated with these insects, PPQ can employ the proper treatment methods so that fly colonies remain healthy. The lab took existing molecular methods that isolate DNA from insects and modified them to isolate DNA from bacterial culture samples. “Our lab identified the isolated bacterial DNA using DNA sequencing technology,” said Farris. “These methods improved previously used commercial methods with increased confidence levels for identifications, and with a cost and time savings to our Agency.”

IMMDL delivered these recent achievements while overseeing Mexican fruit fly activities:

• Evaluated the use of an unmanned aircraft system (UAS) for release of sterile Mexican fruit flies; the study was designed to determine swath width of released flies, effect of simultaneous releases by multiple UAS, and the fly dispersal across the 140-acre citrus groves using fly re-capture data
  

• Developed a backup Mexican fruit fly strain obtained from infested fruit collected around wild larval finds from 2019 to 2020 in Texas’ Lower Rio Grande Valley
  

• Provided training aids and assistance to PPQ canine handlers from Newnan, GA, in training detector dogs for locating Mexican fruit fly larvae in citrus fruit
  

• Provided training and technology transfer to Florida and Texas identifiers on the Ventral Receptacle Compression Technique; this method provides increased level of classifying the female mated status, eliminating false positive mating which can affect determination of quarantines
  

• Continued investigations of X-ray and E-beam as alternative means of sterilizing Mexican fruit flies; the X-ray irradiator meets required dose rate and penetration level, and E-beam evaluations are ongoing
  

• Continued investigations of the potential for nanoparticles to facilitate sterilizing Mexican fruit flies
  

To learn even more about the IMMDL, please visit its web page.