Insecticidal activity bioassay

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. 

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). 

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]. 

For the cytotoxicity against mouse lymphoma cells, renierone and 1,6-dimethyl-7-methoxy-5,8-dihydroisoquinolin-5,8-dione were found to be the most active derivatives with EC50S of 1.1 p,g/mL and 1.7 ig/mL, respectively. From the results obtained, in the described bioassays, it is obvious that the antibacterial and fungicidal activity of the compounds under study is not paralleled by the insecticidal activity towards neonate... 

The preliminary bioassays showed that most of them exhibited moderate insecticidal activity against pea aphids. Compoimd 4a acts on a wide range ofinsect pests via further research, including important species, such as Nilaparvata lugens (LCjqI... 

Unsaturated Amides. In 1971, a group of pungent compounds (isobutylamides) obtained from members of the families Compositae and Rutaceae were described by Jacobsen (Jacobsen, 1971) to have limited use as insecticides. The compounds were characterized as unstable with a marked tendency to polymerize. Examination of extracts of the fruit of the black pepper Piper nigrum, using the aduzki bean weevil as a bioassay, resulted in the isolation of three isobutylamides (13-15) which displayed insecticidal activity (when combined equimolarly) to the pyrethrins (Miyakado et al., 1983, 1989). Based upon the observations of Miyakado and earlier reported test results for synthetic analogs of the compounds described by Jacobsen, Elliot and co-workers defined a basic amide structure to... 

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... 

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. 

Research remains to be done on the residual activity and mammalian toxicity of the chloronitroethane insecticides, but our initial studies on design, directed synthesis, and bioassay indicate there is clearly potential for those compounds in insect control. 

Another factor that influences results of bioassavs for joint action concerns the choice of using either a constant ratio of insecticide to additive or a constant amount of additive whilst varying the dose of the insecticidal component of the mixture. Both methods have their place, the former being most suitable when the results of bioassays have relevance to held application. It is assumed that PBO interferes with processes within the insect which normally degrade [he poison, thus enhancing the activity of the insecticidal component. By applying a constant dose these processes will be equally affected. The amount of additive applied is usually the maximum dose that avoids control mortality in the susceptible standard strain when applied in the absence of the insecticide. 

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