Bioassays insecticidal

In the turnip, the concentration was 63 p.p.m. Toxic action against various insects was established. Two cabbage varieties, cauliflower, brussels sprouts, broccoli, kale, mustard, and kohlrabi also contain 2-phenylethyl isothiocyanate as evidenced by gas liquid chromatography and bioassay. Only root tissues had insecticidal activity. 

Bioassay with mosquito larvae for the detection of insecticide residues in fresh and processed fruits and vegetables is feasible, subject to the limitation that the untreated natural product is in itself nontoxic to the larvae at the dilutions tested. 

The purpose of this work was to determine the toxicity to mosquito larvae of insecticide spray residues. That certain insecticides are translocated in plants (4, 5) adds impetus to this study. Fresh orchard fruit sprayed or dusted with preparations containing parathion (0,0-diethyl O-p-nitrophenyl thiophosphate), tetraethyl pyrophosphate (TEPP, HEPP), DDD [2,2-bis(p-chlorophenyl)-l,l-dichloroethane], DDT [2,2-bis(p-chlorophenyl)-l,l,l-trichloroethane], chlorinated camphene, and basic lead arsenate were shipped from California to Yonkers, N. Y., by air express for bioassay. 

In summary, natural plant compounds have been exploited commercially as sources (e.g., pyrethrins, rotenoids, alkaloids) and models (e.g., pyrethrins, physostlgmine) of insecticides. Other plant compounds are currently being evaluated for similar uses (e.g., chromenes, limonoids). Still others are being evaluated for use in host plant resistance (e.g., long-chain methyl ketones). Such novel chemicals with potent and often unique biological activities will continue to be discovered and exploited through bioassay and... 

Enzymatic techniques have also been employed in the analysis of these compounds. The toxicity of carbamate insecticides is due to the inhibition of the enzyme acetylcholine esterase, so the determination of these compounds can be achieved by enzyme inhibition (2,83,119), bioassay (118,167), or enzyme-linked immunosorbent assay (ELISA) (168-171). In the detection of carbamates by fluorimetric enzyme inhibition, the effluent from a reversed-phase chromatographic column was incubated with cholinesterase, which was introduced via a postcolumn reagent delivery pump. Then, the resulting partially inhibited cholinesterase was reacted with N-methyl indoyl acetate to produce a fluorophore and a reduction in the baseline fluorescence (172). 

In all the studies referred to, the presence of the insecticide is determined by chemical means. The major concern is the biological effect of the material on the ecosystem. In a classical study, Yule (19) determined DDT residues in forest soils and litter using GLC and TLC techniques. Bioassays using Drosophila spp insects were then done on these samples and the mortality equivalent in terms of ug of DDT was determined. The mortality equivalent level of DDT was 50 to 250 times lower than the chemical analysis level. Thus, although the insecticide may be present in the substrate for a period of time extending... 

We used a leaf disk bioassay adapted from Rowland et al.35 to test the insecticidal activity of lichen secondary products on B. tabaci. Two lichen secondary compounds, (-)-usnic acid and vulpinic acid, showed significant results when compared to the controls. Vulpinic acid had an average mortality of 18%, and (-)-usnic acid had an average mortality of 14%. From the dose response of (-)-usnic acid, LD50 was not reached at 1000pM, but a positive correlation was established with increasing concentration and whitefly population response (data not shown). 

Rowland, M., Hackett, B., and Stribley, M., 1991. Evaluation of insecticides in field-control simulators and standard laboratory bioassays against... 

Crystal Blooms. A preliminary examination of crystal blooms of selected insecticides on various species of conifer bark (32) soon demonstrated a wide variation and high unpredictability in crystallization patterns. Because of this variation and the difficulty of bioassay with irregular bark surfaces, fiberboard panels were chosen as the test surface. Fiberboard is not a substitute for bark and does not simulate bark except in a general way and so was used mainly for convenience in studying the potential toxicity of crystal blooms and the broad aspects of crystallization patterns. 

Until now, many substances including pesticides, extracts of plants, and microbial metabolites have been bioassayed to find inhibitory activity on AF production. Organophosphorus insecticides with cholinesterase inhibitory activity, such as dichlorvos (116 in Figure 26), can inhibit AF production by inhibiting the esterase... 

Explanation The appearance of tanned, malformed larvae following treatment with an exogenous compound can be the result of AJH activity or a response on the part of the insect to an external stress such as an insecticide. Since a variety of molecular structures are likely to be tested for AJH activity, it is important to eliminate compounds that are general toxicants at the beginning of the bioassay. 

Manzamine A at 132 ppm dose can induce 80 % growth inhibition of the insect S. littoralis larvae [10]. It also exhibited insecticidal activity toward neonate larvae of S. littoralis, the polyphagous pest insect vfith an ED50 of 35 ppm, when incorporated into an artificial diet and offered to larvae in a chronic feeding bioassay [44]. 

LDsq, and the slope value ( SE). These values are required when we perform a bioassay of insecticide, and the results obtained are to be published in an entomological journal. 

Burchfield, H.P., Redder, A.M., Storrs, E.E., and Hilchey, J.D., Improved methods for rearing larvae of Aedes aegypti (L.) for use in insecticide bioassay, Contr. Boyce Thompson Inst., 17, 317,1953. 

Newly molted sixth instars were fed the host plants for 2 days prior to bioassays. b Larvae were fed Henderson lima bean leaf disks that had been dipped in various concentrations of insecticide suspension. Mortality counts were made after 24 hr. Source From Yu, S.J., Pestic. Biochem. Physiol., 18,101,1982. With permission. 

Brindley, W.A., Al-Rajhi, D.H., and Rose, R.L., Portable incubator and its use in insecticide bioassays with field populations of lygus bugs, aphids, and other insects, /. Econ. Entomoi, 75, 758,1982. 

Chiang, T., M.C. Dean, and C.S. McDaniel. 1985. A fruit-fly bioassay with phos-photriesterase for detection of certain organophosphorus insecticide residues. Bull. Environ. Contam. Toxicol. 34 809-814. 

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