Tobacco, a Natural Aphid Trap

Abstract

The green peach aphid, Myzus persicae (Sulzer), appeared in unprecedented numbers in a few Florida tobacco fields in 1946. The following year this aphid became a major pest, and it was considered a serious threat to tobacco in all the tobacco growing sections of this country and in Canada and Cuba. It was believed that field infestations of the insect developed principally from aphids brought in with plants from infested seed beds. However, there also was a possibility that new colonies were started by winged aphids which entered the fields from outlying areas. To obtain information on this matter, winged aphids resting on tobacco plants in the field were collected and studied in the spring of 1949. Many of them were the green peach aphid, but several other species were taken. Collections were made on five different dates, and a total of 245 specimens were taken. They included 28 different species, several of them represented by single individuals. Eight of the species were new to Florida and four of these were undescribed at the time of collection. Because so many unusual aphids were taken in 1949, this method of collecting was used in several subsequent years. All of the collections were made in Alachua County, Fla. Except for one year, they were made in the experimental tobacco plantings of the Agricultural Experiment Station at Gainesville. In 1962 collections were made in several commercial tobacco fields in the Alachua and Newberry areas. The success of this method of collecting aphids is due to a characteristic feature of the tobacco plant. Both surfaces of the leaves are thickly covered with sticky glandular hairs. Aphids alighting on the tobacco begin to move about, and soon the sticky material of the leaf hairs accumulates on their legs and they become securely trapped. As long as the trapped aphids remain alive, they can be removed from the plants rather easily with a camel's hair brush dipped in 7O0Gc alcohol. Dead aphids stuck to the leaves soon become dry and brittle, and they are of little value as specimens for identification. The collection data for 11 years are summarized in Table 1. Because of variations in the number of collections made in different years and in the number and size of tobacco plants examined, the aphid catches are not directly comparable. The species recorded are representative of the aphids alighting on the tobacco at the collection periods as all aphids seen on the plants were collected. The green peach aphid was taken in each of the 11 collection years. This species flew to the tobacco in very large numbers in 1957, 1961, and 1962, but infestations in tobacco were not severe in Florida during these years. This does not prove that migrating aphids are not a factor in initiating field infestations, but it does show that severe outbreaks do not necessarily follow a heavy influx of flying aphids. Five other aphid species also were taken in all years that collections were made. Four of these, Aphis gossypii Glover, Macrosiphum euphorbiae