Feeding inhibition

Investigation of the contents of the acetone extract of T. tomentosum yielded in total six clerodanes. Although there were some slight differences, all six clerodanes 127—132 were active antifeedants against both S. litura and Plutella xylostella with feeding inhibition values between 60 and 85% at lOpgcm-2 and 55-75% at 5 pgcm-2. Teuflin (128) was the most effective. However, compared with azadirachtin, the effectiveness is still about 10 times less.74... 

Structure (Plant) source Insect tested against Feeding inhibition (%) Concentration (ppm) ec50 (ppm)... 

From the seeds and bark of Samadera indica (Simaroubaceae), indaquassin C (296) was isolated together with three additional quassinoids. Only 296, present in 0.006% in seed kernels, exhibited moderate antifeedant activity toward S. litura, with 1 pg leafcm 2, resulting in 48.9% feeding inhibition.128... 

The predator scents typically used in experiments are urine, extracts of feces, scent gland products, or combinations of these. Behavioral responses of small mammal to predator odor stimuli range from vigilance to avoiding the site, and feeding inhibition. We can test squirrels responses to odors of an arboreal predator (cat), a ground predator (fox), and to humans (in most areas harmless pedestrians, but in others they are squirrel hunters), and compare them with their behavior toward odors of a nondangerous herbivore, such as deer or cattle. 

We will perform the Leaf disk test, also known as leaf disk assay or leaf disk choice test, the second of two bioassays of tannins in the diet of insects in this book. In this often used bioassay, leaf sections of a standard size are treated with the compound(s) in question. Several circular leaf sections ( leaf disks ) (Ali et al. 1999, Filho and Mazzafera 2000, Shields et al. 2008, Wheeler and Isman 2000) or cellulose membrane filters (Hollister and Mullin 1999, Larocque et al. 1999) are presented to a caterpillar in a choice experiment. We measure how much chow the caterpillar has consumed and whether any feeding inhibition is concentration dependent. Regardless of what compounds are being tested, leaf disk tests serve as an important tool in bioassaying feeding inhibitors and stimulants in insects. The cited references are examples of such studies. (In the first tannic acid experiment - Chap. 18 - the tannic acid was mixed into diet in varying concentrations.)... 

Molecules present in the feed inhibit some reactions catalyzed by enzymes. In this problem, the kinetics of inhibition are investigated (from M. L. Shuler and F. Kargi, Bioprocess Engineering, Basic Concepts, Prentice Hall, Englewood Cliffs, NJ, 1992). 

The functional form of the rate equation in Equation (5.3.18) is identical to that of Equation (5.3.17), illustrating that two completely different sets of assumptions can give rate equations consistent with experimental observation. Clearly, more information is needed to discriminate between the two cases. Additional experiments have shown that benzene added to the methylcyclohexane feed inhibits the rate only slightly. In the first case, benzene is expected to compete with methylcyclohexane for available surface sites since M is equilibrated with the surface. In the second case, M is not equilibrated with the surface and the irreversibility of toluene desorption implies that the surface coverage of toluene is far above its equilibrium value. Benzene added to the feed will not effectively displace toluene from the surface since benzene will cover the surface only to the extent of its equilibrium amount. The additional information provided by the inclusion of benzene in the feed suggests that the second case is the preferred path. 

Another type of insecticidal activity is antifeedant activity. A new germacranolide isolated from T. argenteum ssp. argenteum was examined for antifeedant activity against neonate larvae Spodoptera littoral is (Noctuidae). Feeding inhibition of 8a-angeloyloxycostunolide was studied by incorporation of three doses into an artificial diet (Table 9). This compound was found to show antifeedant activity, without any toxic effect itself [33]. 

FRACTL Totalizer for fractionation section feed Inhibition of stacking by pricing gives the model flexi- ... 

Mode of Action. Despite the wide spectrum of insect host range activities displayed by Bt varieties, the mode of action of the insecticidal delta endotoxins is similar. When susceptible insects ingest Bt protein crystals, the first gross symptom observed is feeding inhibition due to paralysis of the digestive tract, including mouth parts. This usually occurs within one hour of ingestion ( ). 

Table II lists those species evaluated for feeding inhibition (FI), growth and development regulation (GR), and toxicity (T) with neem since 1978. Included are 2 species of mites, 25 species of Coleoptera, 10 species of Diptera, 3 species of Heteroptera, 6 species of Homoptera, 1 species of Hymenoptera, 25 species of Lepidoptera, and 9 species of Orthoptera. The total nunber of insect species known to be adversely affected by neem preparations is presently 123, in addition to 3 species of mites and 5 species of nematodes. There is every reason to believe that these nurrbers will increase rapidly, judging by the large nunber of scientists now involved in neem research.

Table II. Arthropods and nematodes evaluated with neem for feeding inhibition (FI), growth regulation (GR), and toxicity (T) (1979-1984).

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