Larvae weevils

Phenazine-l-carboxamide (137) is known as oxychlororaphine and has been isolated from cultures of Pseudomonas chlororaphisit has some limited inhibitory properties, but the inhibitory action of phenazines is generally disappointing. Some phenazine derivatives have insecticidal properties thus, phenazine itself has been found to be toxic to the clothes moth, the Hawaiian beet webworm, the rice weevil and larva of the codling moth, but under trial conditions its toxicity to plant material, as evidenced by severe burning of foliage, was found to be too high to make it of practical value. 

N-Nitroso-N-cyclohexylhydroxylamine is a synergistic agent for insecticides [94] it increases the insecticidal activity ofchlordane. Certain N-alkylphenylnitrosamines [95] and alkyl N-alkyl-N-nitrosocarbamates [96] are insecticides and fungicides, and may also be used for the impregnation of fabrics, etc. They have larvicidal action against Drosophila melanogaster and can also kill all moth larvae and weevils. 

Rice Water Weevil (Lissorhoptrus simplex). Isely and Schwardt (16) who worked with this insect from 1930 to 1933, inclusive, state, The rice water weevil is the most important insect pest of rice in Arkansas. It seems likely that this statement also applies to most of the other rice-producing areas of the southern states. Although the adult weevils feed to a considerable extent on rice leaves, the principal injury is caused by the larvae feeding on the rice roots. Under conditions of heavy infestations practically all the roots are destroyed approximately 4 to 5 weeks from the time of the first flooding of the fields. Normally, even under such conditions, the rice is not killed and when the larvae have matured and ceased feeding, the plants produce a new set of roots and will still produce a crop. The severe setback given the plants during this period naturally results in a marked reduction in yield. 

Dieldrin was then used in a series of 27 quarter-acre plots during the summer of 1953. A third of the plots were treated with dieldrin at the rate of 4 ounces per acre just previous to the first flooding and they were flooded continuously the balance of the season. One half of the untreated plots were drained as larval root feeding approached its peak (July 15) and then reflooded when the soil became dry (July 31). The balance of the untreated plots were continuously flooded. Counts of weevil larvae were taken in each plot twice each week from July 7 to August 14. 

These counts (32) clearly show that the treated plots contained far fewer larvae than either those drained for weevil control or the untreated and continuously flooded plots. The cost of the insecticidal treatment is believed to be less than half as much as draining, drying, and reflooding fields. Counts of mosquito larvae in all plots taken 4 days after the drained plots were reflooded showed less than 1% as many mosquitoes in the undrained plots as in those drained and reflooded. Less water was required for continuous flooding than for draining and reflooding. 

Beetles pass a holometabolous development with several larval instars, pupae (often poorly known), and completely transformed adults. Larvae show biting mouth parts and often possess abdominal cerci-like structures which are absent in adults. The usually short heads of adults may be elongated to form a snout (as in weevils). Antennae and legs, especially the tarsomeres, may vary strongly with species and are taxonomically useful. 

Symptoms Adult weevils eat Irregular holes around the edges of leaves. This damage is more cosmetic than life-threatening. Larvae are the main problem as they feed on plant roots. If a plant is growing poorly, even with no leaves eaten, or suddenly wilts and dies, check in and around the root ball for larvae. 

Microscopic nematode worms, invisible to the naked eye. Some attack plants, while others are beneficial, attacking slugs and larvae of weevils and other pests. See Potato cyst eelworm. 

Mycotoxins can also cause esophageal and liver cancers in humans and are associated with stunting in children. These problems are especially acute in rural Africa where farmers store a years supply of corn in wicker cribs that are open to the sun, weather, infestation by beetle and weevil larvae, and fungal contamination (Wu 2006). 

Espelie, K. E. and Payne, J. A. (1991). Characterization of the cuticular lipids of the larvae and adults of the pecan weevil, Curculio caryae. Biochem. Syst. Ecol., 19, 127-132. 

Trichlorfon is mostly used to kill mangold fly larvae it is also very efficient against the dangerous rice weevil, which can destroy whole harvests. Trichlorfon is successfully used in viticulture (to kill grapevine moths) and pomiculture (to kill apple, pear and plum sawflies, apple ermine moths and gooseberry sawflies). Trichlorfon is very efficient in cot-ton-growing (to kill cotton worms). The low toxicity of trichlorfon for warm-blooded animals accounts for its use in veterinary medicine to combat parasites on large animals. 

In sunflowers, insecticides have been an effective means of control, though the larvae population within the stalk must be quite high (above 80) before a significant effect on yield is realized (Rogers and Jones, 1979). At present, stem weevil does not pose a production problem for Jerusalem artichokes. 

Phosphorus compounds Mulberry moth larva Mosquito larva Image of granary weevil Tropical cockroach intact insects Tropical cockroach insects without intestines... 

Defensive Compounds. Larvae of the weevil Oxyops vitiosa produce a shiny orange secretion that covers their integument and probably acts as deterrent against ants [420]. The composition of the secretion resembles the terpenoid pattern of the host foliage (Melaleuca quinquenervia) from where it is sequestered (concentration about twice that of the host foliage). It contains the sesquiterpene (+)-viridoflorol 230 (Scheme 25), the monoterpene hydrocarbons a-pinene 45, P-pinene 46, limonene 171, a-terpinene 231, and y-terpinene 232 as well as the oxygenated monoterpenesl,8-cineole 58, a-terpineol 233, and terpinen-4-ol 234. 

Control of feeding. Many bean weevils Callosobruchus spp. deposit eggs on kidney beans, but the penetrated larvae do not develop. An unidentified fraction of the bean was found as the growth inhibitor, but it is not lectin. 

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