ESTABLISHMENT OF THE BROWN CITRUS APHID (HOMOPTERA, APHIDIDAE) IN CENTRAL-AMERICA AND THE CARIBBEAN BASIN AND TRANSMISSION OF CITRUS TRISTEZA VIRUS

The brown citrus aphid, Toxoptera citricida (Kirkaldy), is distributed widely on citrus but is not known to occur in the Mediterranean regio n or, until recently, in North America. The brown citrus aphid is an i mportant pest of citrus because it is an efficient vector of citrus tr isteza virus. Surveys have shown that the brown citrus aphid has rapid ly expanded its distribution in the Caribbean Basin and Central Americ a. In September 1991, the brown citrus aphid was found widespread on c itrus in Costa Rica, Nicaragua, and Panama but was not found in Belize , El Salvador, Guatemala, Honduras, or Mexico. In 1992, it was found i n the Dominican Republic, Guadeloupe, Haiti, Martinique, Puerto Rico, St. Croix, St. Thomas, Trinidad, and the U.S. Virgin Islands and, in 1 993, in Cuba and jamaica. The aphid was not found in the Bahamas or Be rmuda in the survey. Enzyme-linked immunosorbent assay tests from citr us trees indicated that citrus tristeza virus incidence was low (<15%) in most areas and probably was caused by the use of infected budwood, rather than by aphid vectors, because of its random pattern of a few infected fields separated by tristeza-free fields. Most citrus tristez a virus isolates detected did not react with the severe-strain discrim inating monoclonal citrus tristeza virus antibody, MCA13, and, thus, a re probably mild strains. Some MCA13 reactive isolates were found in B elize, Costa Rica, Panama, Bermuda, the Dominican Republic, jamaica, P uerto Rico, and Trinidad. The brown citrus aphid was almost-equal-to 6 -25 times more efficient in transmitting several strains of citrus tri steza virus than the melon aphid, Aphis gossypii Glover. Incidence of decline isolates of citrus tristeza virus could increase rapidly with the advancing movement of the brown citrus aphid and could threaten al most-equal-to 180 million citrus trees on citrus tristeza virus-sensit ive sour orange rootstock in the Caribbean Basin, Central America, Mex ico, and the United States. An additional threat exists if this aphid begins to spread grapefruit and sweet orange stem-pitting strains of c itrus tristeza virus.