Plants, terrestrial fenvalerate

Fenvalerate is extremely toxic to representative nontarget aquatic organisms and to some beneficial terrestrial arthropods at concentrations substantially lower than those recommended to control pestiferous insects. Toxic effects are associated primarily with the 2.S, a.S -isomcr and are exacerbated at low temperatures. Birds, mammals, and terrestrial plants are normally tolerant. 

Terrestrial plants are relatively unaffected by fenvalerate at recommended application rates, as judged by negligible uptake of fenvalerate from treated soils, formation of numerous fenvalerate conjugates that are pharmacologically inactive, and metabolism of the liberated cyano group into amino acids and eventually carbohydrate and protein (Miyamoto 1988). 

Synthetic pyrethroids now account for at least 30% of the world insecticide market and are rapidly replacing other agricultural chemicals for control of insect pests. Fenvalerate is one of the more widely used synthetic pyrethroid insecticides. It is derived from a combination of a-cyano-3-phenoxybenzyl alcohol and a-isopropyl phenylacetate ester. Technical fenvalerate is a mixture of four optical isomers, each occurring in equal amounts but with different efficacies against insect pests. Fenvalerate does not usually persist in the environment for >10 weeks, and it does not accumulate readily in the biosphere. Time for 50% loss (Tb 1/2) in fenvalerate-exposed amphibians, birds, and mammals was 6 to 14 h for reptiles, terrestrial insects, aquatic snails, and fish it was >14 h to <2 days and for various species of crop plants, it was 2 to 28 days. Fenvalerate degradation in water is due primarily to photoactivity, and in soils to microbial activity. Half-time persistence in nonbiological materials is variable, but may range up to 6 days in freshwater, 34 days in seawater, 6 weeks in estuarine sediments, and 9 weeks in soils. 

Fenvalerate persists for <10 weeks in the environment and does not accumulate readily in the biosphere. Time for 50% loss (Tb 1/2) in fenvalerate-exposed amphibians, birds, and mammals is 6 to 14 h. For reptiles, terrestrial insects, aquatic snails, and fish, it is usually >14 h to <2 days and for crop plants, it is 2 to 28 days. In nonbiological compartments, Tb 1/2 is up to 6 days in freshwater, 34 days in seawater, 6 weeks in estuarine sediments, and 9 weeks in soils. 

This symptom was hrst reported in 1948 on Andrena flavipes which was repelled by a DDT apphcation [16]. Further assessments were those on M. rotundata [23] and B. terrestris [25], which reacted negatively to residues of the three pyrethroids fenvalerate, deltamethrin, and lambda-cyhalothrin. Visits of plants treated with pyrethroids by M. rotundata females were reduced by 50 percent compared to control. Generally, bees approached the flowers but did not touch them, or if they did, the contact was very brief. This repellency lasted more than 1 hour with fenvalerate and more than 3 hours with deltamethrin [23]. 

---