Pests and diseases can have an adverse impact on agriculture. Pest may include various vertebrates and invertebrates and diseases include micro-organisms, disease agents (bacteria, fungi and viruses), infectious agents, parasites and genetic disorders. Insect-pests of crop plants are the real candidates that will be most affected by global climate change. Complex physiological effects exerted by the increasing temperature and CO2 may affect profoundly, the interactions between crop plants and insect-pest
Global climate warming may lead to altitude wise expansion of the geographic range of insect- pests and increased abundance of tropical insect species. With rise in temperature, the insect-pests are expected to extend their geographic range from tropics and subtropics to temperate regions at higher altitudes along with shifts in cultivation areas of their host plants.
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The studies have shown that, global warming is occurring notably in winter than in summer and is greatest at high latitudes. Increase in temperature in the range of 1 degree C to 50 degree C would increase insect survival due to low winter mortality, increased population built-up, early infestations and resultant crop damage by insect-pests under global warming scenario.
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As stated earlier, the temperature being the single most important regulating factor for insects, global increase in temperature within certain favorable range may accelerate the rates of development, reproduction and survival in tropical and subtropical insects. Consequently, insects will be capable of completing more number of gen-erations per year and ultimately it will result in more crop damage.
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With changing climate it is expected that the growers of crops have to face new and intense pest and disease problems in the years to come. This envises an urgent need to modify crop protection measures with changed climate in order to attain the goal of food security of the nation. Therefore, the impacts of climate change on crop production mediated through changes in populations of serious insect-pests need to be given careful attention for planning and devising adaptation and mitigation strategies for pest management.
Insect management strategies need to be changed in accordance with the projected changes (with shift in cultivation areas of their host crops) in pest incidence and extent of crop losses in view of the changing climate.
Certain effective cultural pest management practices may need to be revised as the new set of pests and diseases are expected to cause the menace. The forewarning models for predicting insect arrivaV infestations based on earlier climate profiles need to be revised in accordance with location specific changes in climate in order to provide precise and accurate forecast of the pest incidence.
There is an urgent need to sensitize the farmers, extension workers and other stakeholders involved in supply chain management about the climate change associated changes in incidence of pests and diseases of major crops in their regions and the different adaptation strategies to cope with the situation. This can be achieved through organization of awareness campaigns, training and capacity-building programmes, development of learning material and support guides for different risk scenarios of pest, etc.
The decision making ability and adaptive capacity of farmers can be enhanced through the integration of a farmers' participatory and multidisciplinary research approach involving research and developmental organizations and farmers as equal partners.
Conservation of natural resources can be promoted among the farmers to adopt environmental conserving pest controlling activities such as organic farming, bio-control, integrated pest management, habitat conservation for important insect pollinators, etc. Strategies for adaptation and coping could benefit from combining scientific and indigenous technical knowledge (ITK), especially in developing countries where technology is least developed.
ITK (indigenous technical knowledge) is helpful to adapt the adverse effects of changing climate. e.g. application of natural mulches helps in suppression of harmful pests and diseases besides moderating soil temperatures and conservation of soil moisture.
The cultural practices include crop isolation, mixed cropping and crop rotation. An important point to note is that the timing of sowing and planting can be planned to allow young plants to increase tolerance before an attack occurs and to reduce the susceptible period of attack. Growing crops that are naturally resistant to diseases and pests also helps.
MECHANICAL AND PHYSICAL CONTROL
With respect to mechanical and physical control, the methods include solar pest trapper, tillage, mowing, mulching, organic soil coverage and barriers. Mechanical and physical methods for controlling pest problems also include sticky traps that use a specific color spectrum to attract insects. Yellow Sticky traps are used to attract and capture a variety of insects such as winged aphids, white flies, etc. Blue sticky traps are used to capture and monitor leaf miners.
BIOLOGICAL CONTROL
Hedges and flowering strips: Farmers can use indigenous shrubs known to attract pest predators and parasitoids by offering nectar, pollen, alternative hosts and/or preys. Most flowering shrub species have this property. However, ensure that you do not use plant species known to be alternative hosts of pests or diseases.
Beetle banks: Strips of grass in the neighbourhood of crop fields harbour different natural pest enemy groups like carabids, staphylinid beetles and spiders. In order to lower the risk of weeds and plants known as host plants of crop pests and diseases, one to three native grass species can be sown in strips of 1-3 m.
Companion plants: Natural pest enemies can also be attracted to companion plants within a crop. These companion plant species can be the same as used in the flower strips.
Both the seeds and leaves of Neem can be used to prepare a neem solution for application as a pesticide. There are different recipes to prepare the solution. Neem seeds contain a greater amount of neem oil, but leaves have the advantage of being available all year. A neem solution loses its effectiveness in about 8 hours after preparation, and when exposed to direct sunlight. Hence, it is ideal to apply the neem solution in the evening, directly after preparation and under humid conditions
PYRETHRUM (A VARIETY OF 'CHANDRAMALLIKA' FLOWER)
Pyrethrum is a daisy-like Chrysanthemum. Pyrethrins are insecticidal chemicals extracted from the dried pyrethrum flower. The flower heads are processed into a powder to make a dust. This dust can be used directly or infused into water to make a spray. Pyrethrins cause immediate paralysis to most insects. Low doses have a “knock down” effect while stronger doses can kill the insects. Pyrethrins break down very quickly in sunlight so they should be stored in darkness.
Various cultural practices and sanitation measures can suppress the spread of diseases and disease-causing organisms. Examples include adopting appropriate plant spacing, and crop rotations.
Growing crop varieties that are naturally resistant to diseases also helps.
Use of disease-free healthy seeds reduces the occurrence of diseases.
Careful destruction of the infected plants as soon as they are noticed in the field helps to avoid further spread of the diseases.
Destroy the stubbles and debris after crop harvest and get rid of any alternate host plants in and around the field that may retain the pathogens from the previous crop cycle.
In greenhouses and shade-nets, one can properly control environmental factors such as ventilation, humidity and temperature thereby controlling diseases/ pathogens that breed in high temperature or high humidity levels.
Using drip irrigation or irrigating early in the morning allows the plants to dry quickly under the sun, thus reducing the length of time the leaves remain wet and reduces the chances of infection.
Using stakes and ropes to support creepers and regular weeding improves air flow through the canopy and allows them to dry quickly, reducing length of wet leaf conditions and thereby the occurrence of diseases.
Ensure good drainage and avoid water logging.
Divide the farm plots using mounds and furrows and avoid flow of water between the sections. Isolate and drain the affected field (except at flowering stage of the crop) and treat the pathogens as soon as possible.
Application of non-synthetic botanical, or mineral inputs
BORDEAUX MIXTURE (COPPER SULPHATE AND LIME)
Bordeaux mixture is both fungicidal and bactericidal, and it can be used on fruits, vegetables and ornamentals under organic farming. As such, it can be effectively used against diseases such as leaf spots caused by bacteria or fungi, powdery mildew, downy mildew and various anthracnose pathogens. The ability of Bordeaux mixture to persist through rain and to adhere to plants is another reason why it is so effective.
NEEM
Both the seeds and leaves of Neem can be used to prepare a neem solution for application as a fungicide. Foliar application of neem leaf extract or neem seed kernel extract in appropriate quantities can be used to treat certain diseases. A neem solution loses its effectiveness in about 8 hours after preparation, and when exposed to direct sunlight. Hence, it is ideal to apply the neem solution in the evening, directly after preparation and under humid conditions.
TRICHODERMA SPECIES
Seed treatment with Trichoderma viride or Trichoderma harizanum (4 gm per kg seed) and soil application of Trichoderma viride or Trichoderma harizanum (25-62.5 kg/ha), preferably along with application of castor cake or neem cake or mustard cake (500 kg/ ha) can help resist some seed borne and soil borne diseases such as root rot, damping off, wilt.
