Methyl Bromide Alternative Boosts Citrus Trade

Attractive navel oranges may remain standard fare in holiday gift packs after a new, chemical-free insect quarantine treatment becomes widely used as an alternative to fumigating citrus with methyl bromide.

Agricultural Research Service scientists at Weslaco, Texas, developed the alternative. Citrus is exposed to forced hot air. The center of each fruit quickly reaches a temperature of 111 degrees Fahrenheit and remains at that temperature long enough to exterminate infesting fruit flies.

The new alternative treatment was developed at the newly named Kika de la Garza Subtropical Agricultural Research Center to be dedicated today. The center includes a new 24,000-square-foot building. ARS is the U.S. Department of Agriculture's chief scientific research agency. ARS Associate Administrator Edward B. Knipling and other officials are scheduled to attend today’s building dedication and renaming in honor of former Rep. Kika de la Garza.

Based upon this research, USDA’s Animal and Plant Health Inspection Service last year approved use of forced hot air treatments for grapefruit, tangerines and thin-skinned Valencia oranges. This year navel oranges were added to the list.

Now, an APHIS-certified forced hot air chamber owned by a cooperative of growers in Mexico is being used to treat up to eight tons of navel oranges at a time. A U.S. produce grower and distributor, Rio Queen Citrus, located in the Rio Grande Valley of Texas, is importing heat-treated oranges and tangerines from Mexico into the U.S. for domestic sales. U.S. distributors exported about 1.18 million tons of citrus in fiscal year 1998, with the majority of fruit grown in areas where treatments are required to insure the fruit is free of fruit flies.

Why may the use of forced hot air treatment become the quarantine treatment of choice? Though citrus treatments involving methyl bromide remain exempt from an international program for phasing out the fumigant, the citrus industry anticipates the fumigant’s cost will increase as less is manufactured. Also, unlike methyl bromide, which may cause the fruit skin to develop a bronze color, the hot forced air treatment causes no impairment to fruit quality. It has even been shown to help protect the citrus from green mold spoilage during transport and marketing.

Scientific contact: Robert L. Mangan and Krista C. Shellie, ARS Kika De La Garza Subtropical Agricultural Research Center, Weslaco, Texas, phone (956) 565-2647, fax 565-6652, mangan@pop.tamu.edu and kshellie@pop.tamu.edu.