Insecticide toxicity and synergism by enzyme inhibitors in 18 species of pest insect and natural enemies in crucifer vegetable crops

Abstract

The toxicities of three enzyme inhibitors and their synergistic effects on four insecticides were studied by using the dry film method on field populations of 18 species of insects collected in Jianxin and Shanjie, China, from 2003 to 2005. Meanwhile, the inhibitory effects of these enzyme inhibitors on the activities of acetylcholinesterases (AChE), carboxyesterases (CarE) and glutathione-S-transferases (GST), in vivo, were also studied. In general, triphenyl phosphate (TPP) and diethyl maleate (DEM) showed low toxicities to six herbivorous pest insects, four ladybirds and eight parasitoids. Piperonyl butoxide (PB) exhibited low toxicities to the herbivorous pest insects and ladybirds, but high toxicities to the eight parasitoids. The tolerance to the insecticides in 11 pest insects and natural enemies was mainly associated with the tolerance to PB. PB showed the highest synergism on methamidophos, fenvalerate, fipronil and avermectin in nine species of pest insects and natural enemies. In general, TPP and DEM showed significant synergisms to these four insecticides in four parasitoid species. However, in contrast to their effects on the parasitoids, the synergistic effects of TPP and DEM on the four insecticides by TPP and DEM against four pest insects and one ladybird varied depending on the insect species and enzyme inhibitor. Activity of AChE, CarE or GST could be strongly inhibited, in vivo, by PB, TPP or DEM, depending on the insect species and enzyme inhibitors. From the results obtained in this study, mixed-function oxidase (MFO) was thought to play the most critical role in insect tolerances to the tested insecticides in the field. Low competition existed in the evolution of insecticide resistance in the field populations of parasitoids, as compared with herbivorous pest insects and ladybirds. Possible causes of the high synergistic effects of PB on the four classes of insecticides, based on multiattack on the activity of CarE, GST or AChE in the insect species, are also discussed.

Surface contact toxicity and synergism of several insecticides against different stages of the tropical bed bug, Cimex hemipterus (Hemiptera: Cimicidae)

“…Other studies have also shown synergism between PBO and fipronil for controlling insects, including the housefly Musca domestica (L.),39–41 the hymenopteran Diaeretiella rapae (McIntoch),42 the homopteran Bemisia tabaci (Gennadius),43 the rice stem borer Chilo suppressalis (Walker)44 and many other important agricultural pests 45. On the other hand, PBO may show an antagonistic effect or no effect with fipronil, for example against the German cockroach Blattella germanica (L.)39, 46 and the western corn rootworm Diabrotica virgifera virgifera (LeConte) 47.…”

Beta carbonic anhydrases: novel targets for pesticides and anti-parasitic agents in agriculture and livestock husbandry

“…Proteinases serving as insect digestive enzymes are defined targets in pest control [10]. Enzyme inhibitors, such as: piperonyl butoxide (PB), a mixed-function oxidase (MFO) inhibitor; triphenyl phosphate (TPP), a carboxyesterase (CarE) inhibitor; and diethyl maleate (DEM), a glutathione S-transferase (GST) inhibitor, have been used to inhibit insect enzymes [11]. Inhibition of Plasmodium falciparum carbonic anhydrase (CA) with aromatic heterocyclic sulfonamides was investigated in 2011 [12].…”

Toxicity and biochemical efficacy of chemically characterized Rosmarinus officinalis essential oil against Sitophilus oryzae and Oryzaephilus surinamensis

“…However, indiscriminate continuous use of synthetic insecticides increases the risk of resistance. Indeed, resistance has already been reported throughout the world with very high levels in Asian and African countries (Pimentel et al, 2007;Wu et al, 2007). Further, resistance species required logarithmically high doses of recommended pesticides that may cause residual toxicity, and adverse effects on non-target organisms, human health, and environments.…”