EFFECT OF LIGHT TRAPS ON HORNWORM POPULATIONS IN LARGE AREAS 
By F. R./Lawson and Cecil R. Gentry, Entomology Research 
Division, and James M. Stanley, Agricultural 
Engineering Research Division, Agricultural 
Research Service 
The tobacco hornworm (Protoparce sexta (Johannson) ) is a major pest of 
tobacco and tomatoes wherever these crops are grown in the United States. The 
tomato hornworm (B. quinquemaculata (Haworth) ) attacks the same crops, but is 
less numerous in most of the tobacco-growing areas. 
The biology of the hornworms has been discussed by Gilmore (1938) 
Madden and Chamberlin (1945), and Metcalf (1909). Morgan and Lyon (1928) found 
that amyl salicylate was attractive to hornworms and developed methods of using 
this bait to trap the moths. These authors reported that when six traps were 
placed in and around a l6-acre field of tobacco in Tennessee, the population of 
eggs and larvae was 2.63 per plant as compared with 6.67 in surrounding fields. 
The next year in a field with eight traps per 8 acres, there were 4.1 hornworms 
as compared with 6.3 in the checks. 
Gilmore and Milam (1933), also working in Tennessee, tested the same 
attractant in devices containing sugar water and tartar emetic. Moths feeding 
from these containers were killed. Feeders were placed at varying densities 
near tobacco fields in areas ranging from 9 to 25 square miles. The percent 
reduction in hornworm populations averaged 51.7 in 1929, 68.9 in 1930, and 53.7 
in 1931. Scott and Milam (1943), again working in Tennessee, tested traps and 
poisoned feeders with the same attractant in a randomized=-block experiment 
consisting of nine treated plots each 1 square mile in area. The results showed 
a percent reduction in the numbers of eggs laid amounting to 62.6 in trapped 
plots and 66.3 in baited plots. 
Stahl (1954) tested bait traps and electric-light traps in North Carolina. 
He stated: "Field studies indicated that the use of either bait or light traps 
had little effect on the abundance of and damage caused by hornworm larvae on 
tobacco at or near the traps." 
For 3 years in succession Stanley and Dominick (1958) placed three black- 
light traps on each of three tobacco fields of about 5 acres in Virginia. The 
mean reduction in number of plants damaged by hornworms was about 16 percent. 
In brief, experiments with bait traps and poisoned feeders in Tennessee 
indicated that these devices reduced the numbers of eggs laid by more than 50 
percent when they were used on areas of 1 square mile or more. On smaller areas 
in North Carolina and Virginia, neither bait nor light traps caused an 
appreciable reduction in hornworm numbers or damage. 
ay) The year after the authors' names is the key to the reference in 
Literature Cited at the end of this report. 
