Effect of pesticides:-

Transcription

1 Introduction Pesticides are substances meant for preventing, destroying or mitigating any pest. They are a class of biocide. The most common use of pesticides is as plant protection products (also known as crop protection products), which in general protect plants from damaging influences such as weeds, diseases or insects. This use of pesticides is so common that the term pesticide is often treated as synonymous with plant protection product, although it is in fact a broader term, as pesticides are also used for non-agricultural purposes. A pesticide is generally a chemical or biological agent (such as a virus, bacterium, antimicrobial or disinfectant) that through its effect deters, incapacitates, kills or otherwise discourages pests. Target pests can include insects, plant pathogens, weeds, mollusks, birds, mammals, fish, nematodes (roundworms), and microbes that destroy property, cause nuisance, spread disease or are vectors for disease. Mealy bugs are sexually dimorphic, meaning that the sexes have distinct morphological differences. Females are nymphal, exhibit reduced morphology, and are wingless, though unlike many female scale insects, they often retain legs and can move. The females do not change completely and are likely to be neotenic (exhibiting nymphal characteristics). Males are winged and do change completely during their lives. Since mealy bugs (as well as all other Hemiptera) are hemimeta bolous insects, they do not undergo complete metamorphosis in the true sense of the word, i.e. there are no clear larval, pupal and adult stages, and the wings do not develop internally. However, male mealy bugs do exhibit a radical change during their life cycle, changing from wingless, ovoid nymphs to wasp-like flying adults. Mealy bug females feed on plant sap, normally in roots or other crevices, and in a few cases the bottoms of stored fruit. They attach themselves to the plant and secrete a powdery wax layer (therefore the name mealy bug) used for protection while they suck the plant juices. The males on the other hand are short-lived as they do not feed at all as adults and only live to fertilize the females. Male citrus mealy bugs fly to the females and resemble fluffy gnats. Some species of mealy bug lay their eggs in the same waxy layer used for protection in quantities of ; other species are born directly from the female.

2 The most serious pests are mealy bugs that feed on citrus; other species damage sugarcane, grapes, pineapple (Jahn et al. 2003), coffee trees, cassava, ferns, cacti, gardenias, papaya, mulberry, sunflower and orchids. Mealy bugs only tend to be serious pests in the presence of ants because the ants protect them from predators and parasites. Mealy bugs also infest some species of carnivorous plant such as Sarracenia (pitcher plants); in such cases it is difficult to eradicate them without repeated applications of insecticide such as diazinon. Small infestations may not inflict significant damage. In larger amounts though, they can induce leaf drop. Many plant essential oils show a broad spectrum of activity against pest insects and plant pathogenic fungi ranging from insecticidal, antifeedant, repellent, oviposition deterrent, growth regulatory and antivector activities. These oils also have a long tradition of use in the protection of stored products. Recent investigations indicate that some chemical constituents of these oils interfere with the octopaminergic nervous system in insects. As this target site is not shared with mammals, most essential oil chemicals are relatively non-toxic to mammals and fish in toxicological tests, and meet the criteria for reduced risk pesticides. Some of these oils and their constituent chemicals are widely used as flavoring agents in foods and beverages and are even exempt from pesticide registration. This special regulatory status combined with the wide availability of essential oils from the flavor and fragrance industries, has made it possible to fast track commercialization of essential oil-based pesticides. Though well received by consumers for use against home and garden pests, these green pesticides can also prove effective in agricultural situations, particularly for organic food production. Further, while resistance development continues to be an issue for many synthetic pesticides, it is likely that resistance will develop more slowly to essential-oil-based pesticides owing to the complex mixtures of constituents that characterize many of these oils. Ultimately, it is in developing countries which are rich in endemic plant biodiversity that these pesticides may ultimately have their greatest impact in future integrated pest management (IPM) programmes due to their safety to non-target organisms and the environment Eugenol from cloves, Eugenia cryophyllus; 1,8- cineole from Eucalyptus globules; citronellal from lemon grass, Cymbopogon nardus; pulegone from Mentha pulegium, and thymol and carvacrol from Thymus vulgaris are among the most active constituents against insects.

3 Eugenol shows variable LD50 values which are purely species specific. Pulegone is shown to be effective against M. domestica, D. virgifera, P. saucia and, S. litura in the range of LD50 = µg/insect (Lee et al., 1997; Harwood et al., 1990; Hummelbrunner and Isman, 2001). Pulegone containing diet at 0.1% retarded development and inhibited reproduction of last instar of southern armyworm, Spodoptera eridania (Cramer) (Gunderson et al., 1985). Pulegone has also been observed to be more toxic than l-menthol against european corn borer, Ostrinia nubilalis (Hubner) 1st instar, where as reverse toxicity was observed against 2nd instar (Lee et al., 1999). cinnamon, (species Cinnamomum zeylanicum), bushy evergreen tree of the laurel family (Lauraceae) native to Sri Lanka (Ceylon), the neighbouring Malabar Coast of India, and Myanmar (Burma) and also cultivated in South America and the West Indies for the spice consisting of its dried inner bark. The spice is light brown in colour and has a delicately fragrant aroma and warm, sweet flavour. Cinnamon was once more valuable than gold. In Egypt it was sought for embalming and witchcraft; in medieval Europe for religious rites and as a flavouring. Later it was the most profitable spice in the Dutch East India Company trade. In modern times, cinnamon is used to flavour a variety of foods, from confections to curries; in Europe and the United States it is especially popular in bakery goods. Cinnamon contains from 0.5 to 1 percent essential oil, the principal component of which is cinnamic aldehyde. The oil is distilled from the fragments for use in food, liqueur, perfume, and drugs.the aldehyde can also be synthesized, Both Cinnamon leaves and bark are used for essential oil distillation, yielding two quite different products. Cinnamon bark contains mostly cinnamaldehyde (60%), while leaf oil consists mostly of eugenol (80%). The root bark is also sometimes distilled and yields up to 60% of camphor. Thus, these oils should not be used interchangeably. The bark oil is highly aromatic, with a sweet, spicy warming, typical Cinnamon scent. It has germicidal and fungicidal properties. Effect of pesticides:- Although there are benefits to the use of pesticides, some also have drawbacks, such as potential toxicity to humans and other animals. According to the Stockholm Convention on Persistent Organic Pollutants, 9 of the 12 most dangerous and persistent organic chemicals are pesticides. A pesticide is any substance used to kill, repel, or control certain forms of plant or animal life that are considered to be pests. Pesticides include herbicides for destroying weeds and other

4 unwanted vegetation, insecticides for controlling a wide variety of insects, fungicides used to prevent the growth of molds and mildew, disinfectants for preventing the spread of bacteria, and compounds used to control mice and rats. Because of the widespread use of agricultural chemicals in food production, people are exposed to low levels of pesticide residues through their diets. Scientists do not yet have a clear understanding of the health effects of these pesticide residues. Results from the Agricultural Health Study, an ongoing study of pesticide exposures in farm families, show that farmers who used agricultural insecticides experienced an increase in headaches, fatigue, insomnia, dizziness, hand tremors, and other neurological symptoms. Evidence suggests that children are particularly susceptible to adverse effects from exposure to pesticides, including neuro developmental effects. People may also be exposed to pesticides used in a variety of settings including homes, schools, hospitals, and workplaces. Effect of pesticide on human and environment food and agriculture organization of united nation. Most pesticides are designed to harm or kill pests. Because some pests have systems similar to the human system, some pesticides also can harm or kill humans. Fortunately, humans usually can avoid harmful effects by avoiding being exposed to pesticides. Humans may be harmed by pesticides in two ways: they may be poisoned or injured. Pesticide poisoning is caused by pesticides that harm internal organs or other systems inside the body. Pesticide-related injuries usually are caused by pesticides that are external irritants.harmful Effects Pesticides can cause three types of harmful effects: acute, delayed, and allergic. Acute Effects Acute effects are illnesses or injuries that may appear immediately after exposure to a pesticide (usually within 24 hours). Human health and environmental issues concern side effects of locust control operations. The main human health issue consists in the use of in appropriate pesticides and formulations or unnecessary exposure during pesticide handling and spraying operations. Plant protection staff and workers involved in these operations are under greater risk but rural populations living in treated areas can also be exposed to pesticides. Environment, i.e. soil, water, vegetation and nontarget organisms, is also under potential threat due to pesticide misuse. Special emphasis must be given to human health and environment in all aspects of locust management, with adoption of appropriate behaviours and specific measures before, during and after control operations. There

5 are currently different ways to significantly reduce undesirable or unforeseen negative impacts of locust control operations using pesticides: Systematic use of protective clothing by staff involved in control operations and pesticide management Updated spraying practices with adequate equipment. This includes barrier treatments (sprayed swaths separate by untreated strips), which limit the quantity of pesticides used, reduce the surface sprayed and create areas free from pesticides within the controlled sites. It also comprises ready-to-use pesticide formulations (such as Ultra- Low Volume ones), which facilitate logistics (no water) and decrease risks for operators and the environment. Use of less harmful pesticides, usually called alternatives to conventional (chemical) pesticides Amongst alternatives to conventional pesticides, two categories are more frequent: the Insect Growth Regulators or IGRs, which are synthetic molecules hampering the moult process (from one hopper instar to the next one); and bio-pesticides using the spores of entomopathogenic fungus specific to locusts and grasshoppers, which grow on the locust cuticle (external skeleton) and whose mycelium develops within the locust body, eventually provoking the death. Information of populations Precautionary measures must be adopted, such as absence from areas under treatments, withholding and re-entry periods, no re-use of empty pesticide containers, etc. Impact of locust spraying operations on human health and the environment also needs to be monitored. This includes assessment of their potential effects on human health (operators and local populations) and fauna (non-target organisms such as beneficial arthropods, birds, mammals, reptiles, aquatic fauna, etc.) as well as sampling for pesticide residues in soils, water, vegetation, fauna, etc. in order to detect and evaluate any side effects -and correct them if needed. Training and refreshing of plant protection staff and operators involved in control operations, monitoring of control operations (quality and efficacy) and pesticide management (handling, transport, storage, clean-up and disposal) are pre-requisites for improving human health and environmental aspects in locust management. Awareness raising and education of

6 concerned local populations is also necessary, together with information of decision makers. The fungicidal activity makes T. viride useful as a biological control against plant pathogenic fungi. It has been shown to provide protection against such pathogens as Rhizoctonia, Pythium and even Armillaria. [2] It is found naturally in soil and is effective as a seed dressing in the control of seed and soil-borne diseases including Rhizoctonia solani, Macrophomina phaseolina and Fusarium species. When it is applied at the same time as the seed, it colonizes the seed surface and kills not only the pathogens present on the cuticle, but also provides protection against soil-borne pathogens. Plant use for insect control. 1) Eugenol from cloves, Eugenia cryophyllus; 2) 1,8- cineole from Eucalyptus globules; 3) citronellal from lemon grass, Cymbopogon nardus; 4) pulegone from Mentha pulegium, and 5) thymol and carvacrol from Thymus vulgaris. Need of work:- Due to harmful effect of chemical pesticide on human, animal, and environment and delayed biological response it force to develop new ecofriendly pesticide those effective, safe and natural degradable.