Issue No. 111
H. V. Weems, Jr.
Introduction
A whitefly, Aleurodicus dispersus Russell, now distributed over much of the Florida keys, is the prime suspect vector of a deadly virus disease of coconut palms, lethal yellowing, which has caused the loss of more than ninety per cent of the native coconut palms of the Key West area within the last 15 years. The disease was confined to the western-most Florida Keys until 1970; however, a new infestation has been discovered recently on Key Largo Key, accompanied by an extension of the range of A. dispersus into the eastern-most or upper Keys. While the evidence is circumstantial that in Florida A. dispersus is the primary, if not the sole vector of the lethal yellowing disease of coconut palms, it remains the most likely suspect. Recently an english scientist, Norman Grylles, apparently established a relationship between the disease and whiteflies. He reported that he had transmitted lethal yellowing from a diseased coconut palm to a healthy palm with another species of whitefly in the same genus–Aleurodicus coccolobae Quaintance and Baker–as the vector. Although he was successful in achieving only one transmission of the disease, indicating that whiteflies are inefficient vectors, he did show that they can be vectors of lethal yellowing. Since the disease now endangers many thousands of coconut palms on the southern Florida mainland, the possibility of A. dispersus being the primary vector is of major concern to regulatory and research workers in Florida. However, the concern over the spread of this whitefly onto the mainland of Florida is not only because of its possible relationship to the spread of the lethal yellowing disease. This whitefly often occurs in great numbers and attacks many species of plants, including citrus, avocadoes, bananas, mangoes, and a wide variety of ornamentals. Its potential danger to these plants is sufficient cause for concern. Damage to the plants is inflicted by both immatures and adults sucking sap from the leaves of plants. An objectionable sooty fungus which interferes with photosynthesis often grows on the droplets of honeydew secreted on the foliage by whiteflies.