ARS | Publication request: Imidacloprid in Melon Guttation Fluid: A Mode of Exposure for Pest and Beneficial Organisms

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 29, 2011
Publication Date: February 1, 2012
Citation: Hoffmann, E.J., Castle, S.J. 2012. Imidacloprid in Melon Guttation Fluid: A Mode of Exposure for Pest and Beneficial Organisms. Journal of Economic Entomology. 105(1):67-71.

Interpretive Summary: Imidacloprid is a widely-used pesticide used to control a number of crop pests. It can be applied as a spray on the plants directly, or in the soil where it is taken up by the roots and transported by the plant vascular system to the other plant tissues. Under certain environmental conditions, xylem vascular fluid can be expelled onto the leaf surface in a process called guttation. Many animals use this liquid (often confused with dew) as a water source. There are few reports on the levels of imidacloprid in guttation fluid after a soil application. When imidacloprid was applied to the soil of young melon plants, we found the material was transported in the xylem and detected in the guttation fluid within a week of the treatment. A commercially-available ELISA test was used for detecting the imidacloprid, and the concentrations exceeded the reported LD50 values for several pest and beneficial insect species. Pesticides in guttation fluid are a relatively unexplored route of exposure for both pest and beneficial insects, and could represent an important exposure path for both of these groups.

Technical Abstract: ELISA techniques were used to detect imidacloprid in guttation fluid of young cantaloupe plants in Arizona. Imidacloprid was detected at up to 37 µg / ml (ppm) one d after a label rate soil application. These imidacloprid titers exceed reported median oral toxicities for several insect species by factors of 10 or more. Pesticides in guttation fluid are a relatively unexplored route of exposure for both pest and beneficial insects, and could represent an important path for both of these groups.