Insects bollworms

A SN reaction-based domino route to clerodane diterpenoid tanabalin (2-488) [258] has been described by Watanabe s group (Scheme 2.111) [259]. This natural product is interesting as it exhibits potent insect antifeedant activity against the pink bollworm, Pectinophora gossypiella, a severe pest of the cotton plant The domino sequence towards the substituted trans-decalin 2-487 as the key scaffold is induced by an intermolecular alkylation of the (5-ke toes ter 2-484 with the iodoalkane 2-483 followed by an intramolecular Michael addition/aldol condensation (Robin-... 

The pink bollworm (Pectinophora gossypiella Saund.), considered to be potentially the worst pest of cotton in the United States, occurs throughout the major cotton-producing areas in Mexico, Venezuela, Colombia, Brazil, and Argentina. It probably causes more damage to cotton in the tropical Americas than any other insect. 

Cuts from the silica gel column were incorporated into artificial diets optimized for several economically-important agricultural pest insects, the pink bollworm Pectinophora gossypiella> the tobacco budworm Heliothis virescens> the corn earworm H. zea and the fall armyworm Spodoptera frugiperda. > Monitoring with this artificial diet bioassay, further column chromatography and preparative TLC on silica gel in diethylether-petrol yielded five... 

Insects may emit as little as 10 g of pheromone and a female insect contains typically only 50 mg of the material. The structure is sometimes exacting, as in the case of the pink bollworm, where the ratio of cis and trans double bonds is species specific to avoid hybridization of insects. 

While the above observation is interesting and could possibly have some implications for the control of the pink bollworm, the complexity of the steroid nucleus of ponasterone A and other molting hormone analogs and their weak insecticidal effect when applied topically or administered orally to most species of economically important insects may preclude their commercialization. The only commercial use of the molting hormone analogs thus far has been in the sericultural industry for the synchronization of cocoon spinning of silkworm colonies (17). 

Insecticidal control of the pink bollworm is yet another management practice used by growers in Arizona pink bollworm exit holes in cotton bolls might provide portals of entry for A. flavus (55). Unfortunately, it is not economically feasible to achieve 100% control of the pink bollworm in cotton through the hi -ftequency use of insecticides, and even relatively low levels of infestation by this insect pest is well correlated to high levels of A. flavus infection and subsequent aflatoxin contamination. 

The effects of selected fatty acid (Cio-Cia) methyl esters on the pink bollworm (Pectinophora qossypiella). bollworm (Heliothis zea) and tobacco budworm (Heliothis virescens) were determined, and a number of cyclopropyl, olefinic and acetylenic methyl esters were also tested (115). Methyl (Z,Z)-deca-2,8-diene-4,6-diynoate (matricaria ester) was lethal at low concentrations to all three insects. This last ester was isolated from Conyza canadensis but is found in vegetative matter of many plants of the Asteraceae. 

It was toxic to the pink bollworm at 0.005% and to the bollworm and the tobacco budworm at 0.15% in artificial diets. Esters (C10-C12) were also toxic to the insects as sprays. Matricaria ester was also shown to be a potent insect antifeedant compound to these insects (115). 

Most acetylenic compounds in plants are derived from meta-bolically altered fatty acids. These often are active in plant-insect relationships. 8-cis-Dihydromatricaria acid is also found in the defensive secretion of the soldier beetle (Chaulioqnathus 1econtei) (125), and has subsequently been shown to have anti-feedant properties against Phidippus spp. (jumping spiders) (126). As previously mentioned matricaria ester has antifeedant properties to the pink bollworm, bollworm and tobacco budworm (115). 

Figure 4. Electron micrograph of a pink bollworm, Pectinophora gossypiella, after ingestion of the crude methanol extract of Ajuga remota roots. This insect has three head capsules that mask its functiorml mouthparts- The insect eventually starved to death. Magnification X 113.

Figs. 3 and 4 are electron micrographs of a fall armyworm, and a pink bollworm, respectively. Both Insects have three head capsules because they underwent two failed molting cycles before death. That Is, even though feeding became Impossible after the first Inhibited ecdysls because the adhering second head capsule covered the mouthparts, these larvae could synthesize a third head capsule. ... 

Different lines, each with Insect resistance, may possess different ratios of antibiotic compounds. Thus, It may be possible to Increase resistance by crossing lines where each contributes genes for biosynthesis of different antibiotic compounds. The tobacco budworm was selected for study In preference to the cotton bollworm because It Is easier to rear and use In the laboratory, Is more resistant to Insecticides In the field, and It Is approximately as susceptible to cotton constituents Incorporated In laboratory diets (14). This present study was carried out to Identify and analyze for cotton constituents that were toxic In laboratory feeding tests, and to determine whether there were positive correlations of their content In leaves and/or other tissue with field resistance. From this Information, the generation of lines with multiple factors for resistance could be Initiated. 

Selection for altered pheromone-component ratios in the pink bollworm moth, Pectinophora gossypiella (Lepidoptera Gelechiidae). Journal of Insect Behavior 2 609-621. 

Insects make unsaturated as well as saturated hydrocarbons. The former as well as long-chain alcohols and their esters often form the volatile pheromones with which insects communicate. Thus, the female pink bollworm attracts a male with a sex pheromone consisting of a mixture of the cis,cis and cis,trans isomers of 7,11-hexadecadienyl acetate,13 and European corn borer males are attracted across the cornfields of Iowa by czs-ll-tetradecenyl acetate.14 Addition of a little of the trans isomer makes the latter sex attractant much more powerful. Since more than one species uses the same attractant, it is possible that the males can distinguish between different ratios of isomers or of mixtures of closely related substances. 

Uses insecticide to control aphids, scale insects, jassids, lepidopterous larvae, bollworms, mealybugs, psyllids, thrips, spider mites, etc. in citrus fruit, pome fruit, olives, cotton, cereals, rice, coffee, tea, sunflower, sugar cane, tobacco, ornamentals, and vegetables also used as acaricide and for control of mosquito larvae. 

One of the major reasons for the interest in insect pheromones is their potential for use to control pests. In one method a large number of traps, baited with small amounts of the sex attractant of the female insect, are used to trap enough males that the breeding of the insects is decreased. In another method that requires fewer traps, a small number of traps are used to monitor the population of the target insect. The best time to apply pesticides can be determined by monitoring these traps. In one case, 10 to 15 applications of a pesticide to control the pink bollworm still resulted in damage to 30% of a cotton crop. This was decreased to almost no damage with only one to two pesticide applications when the ideal times for these applications were determined by the use of traps. 

A Comparison of Pheromone, Pheromone and Pyrethrold and Insecticides for Control of the Pink Bollworm In the Imperial Valley, CA." USDA, 1981, Butler G. D. and Barker R. J. Klassen, W. Rldgway, R. L. Inscoe, M., In "Insect Suppression With Controlled Release Pheromone Systems" Kydonleus,... 

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