A Mated Fruit Fly in a Backyard Mango Tree Puts 19 Square Miles of Port Isabel Under Quarantine

The trap was hanging in a mango tree on a residential lot in Port Isabel, and what came out of it was not an interception. It was a mated female West Indian fruit fly, which is the difference between a hitchhiker that arrived in a piece of fruit and a population that is already reproducing in Cameron County.

The U.S. Department of Agriculture's Animal and Plant Health Inspection Service established a West Indian fruit fly quarantine over Port Isabel on Oct. 7, acting in cooperation with the Texas Department of Agriculture. It covers 19.19 square miles and, in a detail that matters for how this one plays out, contains no commercial agriculture. The state quarantine it formalizes is dated Aug. 21.

Port Isabel sits at the southern end of the Laguna Madre, across the causeway from South Padre Island, in a county where backyard mango, citrus and hog plum are ordinary landscaping rather than crops. The West Indian fruit fly — Anastrepha obliqua, established across Mexico, Central and South America, Puerto Rico and the U.S. Virgin Islands — lays its eggs into the flesh of a ripening host. The larvae tunnel as they feed, and the fruit is finished as anything anyone would eat. APHIS does not consider it native to the continental United States, Hawaii or the other territories.

Once a quarantine is up, the paperwork starts. APHIS is restricting interstate movement of regulated articles out of the zone and running what it calls safeguarding measures to keep the fly out of non-infested areas and out of export channels, while the agency and TDA work a joint program of survey, treatment and regulatory action aimed at eradicating what APHIS describes as a transient population.

What the announcement leaves out is the part growers and residents in the Valley will want first: how many flies the delimiting survey has turned up, how far the infestation extends beyond the trap line, and when treatments begin. The release gives the detection, the acreage and the legal machinery. Nothing on the fly count.

The timing is the uncomfortable part. APHIS and TDA announced on Aug. 20 that they had removed fruit fly quarantines across the lower Valley, releasing 212.64 square miles that included 1,138.61 acres of commercial citrus — the sapote fruit fly zones around Harlingen, Rio Hondo and Alamo — and, separately, the West Indian fruit fly quarantine covering the Palmview area of Hidalgo County, 68.2 square miles and 495.7 acres of citrus. Both species were declared eradicated using approved program control methods.

The TDA quarantine for Port Isabel is dated one day after that announcement. That is a sequence, not a proven link: APHIS has not said the Port Isabel fly is related to the Palmview population, and the two zones are in different counties with different host landscapes. What is clear is that the program did not get a season off. The Palmview zone was worth nearly 500 acres of commercial citrus. The Port Isabel zone is worth no commercial acreage at all, which tells you something about where this insect is finding its hosts — in yards, not in groves.

Between the Mexican fruit fly quarantine in Zapata County this spring, the sapote and West Indian zones that closed in August, and now Port Isabel, Texas has handled three Anastrepha species in one year. Each is a separate quarantine and a separate eradication campaign, and each one begins the same way, with a trap in a fruit tree somebody planted for the shade.

Maps of the current federal fruit fly quarantined areas, and the host list that defines which fruit cannot move out of Port Isabel without paperwork, are published on APHIS's exotic fruit fly pages. If you are moving fruit from the south end of Cameron County this month, that list is the one to read before the truck leaves.