Diflubenzuron persistence

Table 17.2 (continued) Diflubenzuron Persistence in Soil and Water... 

Mobility and leachability of diflubenzuron in soils is low, and residues are usually not detectable after 7 days. In water, half-time persistence (Tb 1/2) is usually less than 8 days and lowest at elevated temperatures, alkaline pH, and high sediment loadings (Fischer and Hall 1992) (Table 17.2). Increased concentrations of diflubenzuron in soils and waters are associated with increased application frequency, flooding of treated supratidal areas, wind drift, and excessive rainfall (Cunningham 1986). 

Apperson, C.S., C.H. Schaefer, A.E. Colwell, G.H. Werner, N.L. Anderson, E.F. Dupras, Jr., and D.R. Longanecker. 1978. Effects of diflubenzuron on Chaoborus astictopus and nontarget organisms and persistence of diflubenzuron in lentic habitats. Jour. Econ. Entomol. 71 521-527. 

Harrahy, E.A., M.J. Wimmer, S.A. Perry, D.C. Faber, J.E. Miracle, and W.B. Perry. 1993. Persistence of diflubenzuron on Appalachian forest leaves in stream water. Jour. Agricul. Food Chem. 41 2191-2196. 

Sundaram, K.M.S., S.B. Holmes, D.P. Kreutzweiser, A. Sundaram, and P.D. Kingsbury. 1991. Environmental persistence and impact of diflubenzuron in a forest aquatic environment following aerial application. Arch. Environ. Contam. Toxicol. 20 313-324. 

Aquatic Ecosystem and Fish. Metcalf et al. (2) studied the fate of diflubenzuron (radiolabeled separately in three different positions) in their model ecosystem. Diflubenzuron was dubbed "moderately persistent" in algae, snails, salt marsh caterpillars, and mosquito larvae as evidenced by limited biodegradability (Table IV). However, diflubenzuron and its nonpolar metabolites were not prone to ecological magnification in Gambusia fish. The lack of bioaccumulation of diflubenzuron residues in fish was substantiated by Booth and Ferrell (14) who used the channel catfish, Ictalurus, in a simulated lake ecosystem. They treated separate soil samples at 0.007 and 0.55 ppm, respectively. 

Moffet MF, Anderson LE, Corry T, Hanratty MP, Heinis LJ, Knuth ML, Liber K, O Halloran SL, Schmude KL, Stay FS, Tanner DK. 1995. Effects, persistence and distribution of diflubenzuron in littoral enclosures. Duluth, (MN) USEPA, Mid-Continent Ecology Division. 

Table 3 Persistence of diflubenzuron on plant leaves two months after topical application in a greenhouse study ( J ) ...

From the results it is clear that no residues were found up to the sensitivity limit of the analytical methods used. Furthermore untreated leaves were found to contain practically no radioactive material. It can be concluded that diflubenzuron after application on plants is very persistent and has no systemic properties. In other studies it was found that diflubenzuron does not permeate through the cuticular barrier into the leaves of broad bean. These studies on the fate of diflubenzuron on and in plants will be published more extensively elsewhere ( J ) Essentially the same results were obtained by Still in a study on the metabolic fate of diflubenzuron on cotton plants ( 2). In addition to metabolism, other factors might influence the fate of diflubenzuron on plants, i.e. washing off and photochemical degradation. Ruzo et al. (jQ) and Metcalf et al. (30)... 

Summarizing, diflubenzuron features mentioned in the introduction of this paper can be completed as follows The new insecticide has favourable environmental properties because it is non-persistent in soils and it has a low biological magnification. It is stable on plants and in insects, hence it has a long residual activity. It represents the best choice from the series of the benzoylphenyl ureas. It is a reversible inhibitor of chitin synthesis in insects, probably by blocking chitin synthetase. 

Mobility and leachability of diflubenzuron in soils is low, and residues are usually not detectable after 7 days in water half-time persistence (Tbl/2) is usually less than 8 days and... 

Diflubenzuron applied aerially to forest leaves in the spring growing season did not persist when the leaves were placed in sAeam water. Residues on oak leaves decreased 36% in July, and 23% in August within the flrst... 

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