Control of Pests and crop Disease
- Agriculture is the single largest sector of India that provides the principal means of livelihood for over 58.4% of country’s population. It contributes approximately one-fifth of the total gross domestic product (GDP).
- Agriculture accounts for about 10% of the total export earnings and provides raw material to a large number of industries, however, low and volatile growth rates and the recent escalation of agrarian crisis in several parts of the Indian countryside are a threat not only to national food security but also to economic wellbeing of the nation as a whole.
- To satisfy the growing demand of fruits and vegetables, farmers in the country utilize pesticides to boost production and to prevent insect-pests and diseases, which pose great threats to vegetable and fruit production.
- It has also been reported that pesticides are commonly used on periodic basis throughout the growing season at very high concentration. Such a use of pesticides during production often leads to the presence of pesticide residues in fruits and vegetables after harvest.
- In addition, the usage of these chemicals has occasionally been accompanied by serious risks to both human health and the environment because of their toxic potential, high persistence, bio-concentration, and especially, due to their nonspecific toxicity. Some of the pesticides are persistent, and hence, they remain in the body causing long term exposure.
Pesticide residues
- Pesticides residues have been defined as any specified substance in food, agricultural commodities, animal feed, soil, or water, resulting from the use of pesticide.
- The term includes any derivatives of a pesticide such as conversion products, metabolites, reaction products and impurities that are of toxicological significance.
Effects of Pesticides
The health effects of pesticides may be acute or delayed in workers who are exposed to pesticides.
Acute effects
- A large number of reports are available on acute effects associated with occupational exposure to pesticides. These exposures may be accidental, occupational, or intentional. A review on unintentional pesticide poisoning in 35 countries has been already published.
- The acute health problems, such as dizziness, headaches, abdominal pain, nausea, vomiting, as well as skin and eye problems, skin conditions, seizures, coma and even death may occur in workers that handle pesticides. Mild to moderate pesticide poisoning mimics intrinsic bronchitis, asthma, and gastroenritis.
Long-term Health Effects
- Neurological problems: Strong evidence links pesticide exposure to worsened neurological outcomes. The risk of developing Parkinson’s disease is 70% greater in those exposed to even low levels of pesticides. People with Parkinson’s were 61% more likely to report direct pesticide application.
- Fertility: A number of pesticides like2,4-D and dibromochlorophane has been associated with impaired fertility in males.
- Reproductive effects: Pesticides, lethal to dividing cells of genitalia, may cause abnormalities in sperms leading to decrease their ability for fertilization. On the other hand, the ova become defective and not able to implant on the uterine surface, leading to early abortion or miscarriage. Hormone disruption: Some substances cause physical birth defects and others can cause subtle hormonal effects on the developing fetus or can affect a child’s functional capacities.
- Hormone disruptors have been linked to many health problems including reproductive cancers. The drug diethylstilbestrol (DES), which was given to pregnant women to prevent miscarriage between 1941 and 1971 worked as an endocrine disrupting chemical on the developing fetus. Decades later, many of these DES exposed daughters developed cervical cancer.
- Twenty-four pesticides still in the market, including 2, 4-D, lindane and atrazine, are known endocrine-disrupters. Steroid hormones, such as oestrogens, androgens (e.g., testosterone) and progesterone, are crucial for primary sex determination, foetal development and acquisition and maintenance of secondary sexual characteristics in adults.
- Chemicals, including many pesticides, with similar structures to these hormones can interfere with their function and lead to a variety of developmental and reproductive anomalies.
What is natural pest and disease control?
- Pests and diseases are part of the natural environmental system. In this system there is a balance between predators and pests. This is nature’s way of controlling populations.
- The creatures that we call pests and the organisms that cause disease only become ‘pest and diseases’ when their activities start to damage crops and affect yields.
- If the natural environmental system is imbalanced then one population can become dominant because it is not being preyed upon.
- The aim of natural control is to restore a balance between pest and predator and to keep pests and diseases down to an acceptable level.
- The aim is not to eradicate them altogether, as they also have a role to play in the natural system.
- Once a pest or disease has started to attack a crop, the damage cannot be repaired and control becomes increasingly difficult. Where possible, use techniques to avoid or prevent pest and disease attack in the first place.
Methods of Pest and Disease Control
- A healthy soil
- A healthy crop
- Resistant varieties
- Rotation
- Good hygiene
- Soil tillage
- Soil pH
- Timely sowing
- Companion planting
- Plants to attract predators and
- parasites
- Barriers
- Traps
- Light traps
- Fly traps
- Hand picking
- Biological control
- Natural pesticides
- Social prevention
Alternatives to pesticides
- Alternatives to pesticides are available and include methods of cultivation, use of biological pest controls (such as pheromones and microbial pesticides), genetic engineering and methods of interfering with insect breeding.
- Application of composted yard waste has also been used as a way of controlling pests. These methods are becoming increasingly popular and are often safer than traditional chemical pesticides. In addition, Environmental Protection Agency (EPA) is registering reduced-risk conventional pesticides in increasing numbers.
- Cultivation practices include polyculture (growing multiple types of plant), crop rotation, planting crops in areas where the pests that damage them do not live, change in planting time according to when the pests will be least problematic and use of trap crops that attract pests away from the real crop.
- In the United States, the farmers control the insects successfully by spraying hot water at a cost, which is about the same as the pesticide spraying. Release of other organisms that fight the pest is another example of an alternative to pesticide use.
- These organisms can include natural predators or parasites of the pests. The bio-pesticides based on entomo-pathogenic fungi, bacteria and viruses causing diseases in pest species can also be used for controlling the diseases in vegetable crops.
- Interfering with insects’ reproduction can be accomplished by sterilizing males of the target species and releasing them so that they mate with females but may not produce offspring. This technique was first time used on the screwworm fly in 1958 and since then it has been used with the medfly, the tsetse fly and the gypsy moth.
- However, this can be a costly and time-consuming approach, which works only on few types of insect. Another alternative to pesticides is the thermal treatment of soil through steam.
- Raising soil temperature by passing steam through the steel pipes laid down into the soil 45 cm below the surface kills the pests and improves the soil health.
- In India, traditional pest control methods include Panchakavya (the mixture of 5 products). The method has recently experienced resurgence in popularity due in part to use by the organic farming community.