Environmental benefits realized from eradication of the non-indigenous insect Anthonomus grandis Boheman, the cotton boll weevil

Abstract

At least one third of the insecticide used in agriculture has been used to control the boll weevil in cotton. Historically, these insecticides have been toxic to humans and harsh on the environment. In addition, the intensive use of chemical insecticides to control the boll weevil results in the disruption of naturally occurring biological control factors that regulate other insect pest populations causing a chain reaction of secondary pest populations that require treatment followed by resurgence and repeat treatment. This situation has resulted in the development of resistance to insecticides, high control costs and unacceptable levels of chemical insecticide contamination in the environment. The boll weevil eradication program was instituted, in part, in an attempt to curtail the adverse environmental effects of traditional boll weevil control practices. A statistical analysis of 23 restricted use pesticides use in Louisiana cotton from 1991 through 2003 revealed that there was a significant change in the use of seven of these insecticides from the time before eradication (1991-1998) and during eradication (1999-2003) in Louisiana. Of these seven, five showed a significant decrease in use and two showed a significant increase in use. Impact quotients developed to take into account the annual use of each insecticide plus the toxicological values and environmental influence of each insecticide indicate that the insecticides with a significant change in use had a smaller mammalian toxicological impact quotient (MTIQ) during eradication than before eradication. The ecotoxicological impact quotient (EcoTIQ) increased dramatically during eradication as compared to before eradication and the environmental impact quotient (EnvIQ) increased slightly over the same period. In all cases, the MTIQ remained substantially lower than the EcoTIQ and EnvIQ in any given year and as eradication progressed and malathion use declined, so did the impact quotients and insecticide use, especially methyl parathion. As eradication of the boll weevil in Louisiana nears completion, a continued reduction in all three quotients is expected.