Cold Treatment and Foreign Insects

Each year, thousands of tons of fruit enter into U.S. commerce from foreign countries. Many of these countries are home to insects that do not occur in the United States. Non-native species can wreak havoc on local environmental and agricultural resources. The United States Department of Agriculture’s Animal and Plant Health Inspection Service is tasked with preventing these foreign insects from establishing populations in the U.S. One of the treatments required by the USDA to be conducted on foreign fruit before it enters the country is cold treatment.

Medfly and Other Pests

Cold treatment consists of maintaining produce at a specific temperature for a specific period of time. Various cold treatment schedules have been found to have deleterious effects on economically important insects such as the tephritids. The tephritidae, or picture fruit flies, are the most important family of flies to agriculture. This group includes Ceratitis capitata, the Mediterranean fruit fly, or Medfly.

Tephritids should not be confused with the small vinegar flies such as Drosophila melanogaster, which are commonly called ‘fruit flies’ and are often found to be present near overripe fruit. Many of the tephritids attack fruit on the tree or vine, causing unsightly damage or total fruit loss. They are serious pests in Europe, Africa, Central and South America, causing billions of dollars of damage to crops as well as necessitating the use of tons of chemical insecticides. It is important to keep them from establishing breeding populations in North America.

How Is Cold Treatment Done?

Usually fruit undergoes cold treatment onboard refrigerated cargo vessels. These ships, commonly called reefers, have temperature sensors built into all the cargo holds. The sensors are connected to a central computer which is often located in the engine control room. This computer prints out the temperatures of the fruit at hourly intervals.

For example, clementines coming into the U.S. from either Morocco or Spain are required to be held onboard the vessel under 34 degrees Fahrenheit for a minimum of 14 days, or 16 days under 35 degrees or 18 days under 36 degrees Fahrenheit. This treatment will kill Medfly larvae (Ceratitis capitata) that are commonly found in the fruit. Schedules vary depending on the specific insect, where the fruit was grown and the type of fruit. USDA - APHIS inspectors meet the cargo vessels on their arrival into U.S. ports and check the temperature records.

Does it Harm the Fruit?

Cold treatment is well tolerated by deciduous fruit, such as apples, pears and grapes. Other treatments, such as hot water dips, irradiation and fumigation are used on tropical fruits and other imported produce depending on the origin of the commodity and the insects commonly found there.

The use of temperature to prevent potentially disastrous infestations in the U.S. is an environmentally sound technique. Even organically produced commodities can be treated in this way without losing their organic certification. Cold treatment is an efficient, cost-effective and environmentally neutral method for killing foreign insects in imported fruit. For more information about food and import requirements visit the USDA – APHIS website.

Entering the Harbor

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