Authors: Shailendra Kumar and Neha Upadhyay
Tomato, capsicum and cucumber are most preferred vegetable crops used to cultivate under protected structure in India. High productivity, quality fruits and year round production are special features that encouraging the farmers to adopt polyhouse technology. Government is providing various subsidy plans for adapting polyhouse, quality seed, drip irrigation and various other modern technologies. But still there is gap between adaptation and success of polyhouse technology for small farmers. Incomplete knowledge of crop cultivation package and lack of guidance is playing a key role to limit success in polyhouse technology for new growers.
Knowledge of suitable varieties, raise healthy nursery, soil health management, planting, nutrition, irrigation and plant protection are technical aspects need to grower for successful cultivation of crop under polyhouse. Often these attributes are mostly address by local progressive growers, institute or horticulture department to new growers but still it has been notices that major problem faced by grower in polyhouse cultivation is insects and diseases infestation. Due to incomplete knowledge of pest management, grower fails to get potential yield of crop and quality fruit often produce in polyhouse but sometime conditions get too harsh that complete failure of crop occurs without any return.
Favorable environmental conditions as high humidity, temperature regulation, optimum light intensity, etc create microclimate under polyhouse that promote plant growth but also favor insect and disease development and establishment. Once pest and disease is established in polyhouse it is very difficult to eradicate. Thereby loss in yield, reduction in fruit quality, increment in input cost and sometime complete failure of crop occurs. Damping off, Powdery mildew, leaf spot and leaf blight are of common occurrence while aphid, thrip, mite, whitefly and fruit borer infest crop under polyhouse.
Source of infection: Generally protected structures are design to protect crop from all adverse condition including insects and diseases. Nevertheless, it is hard to prevent most insect and diseases to enter in polyhouse. The windblown fungal spores (early blight, late blight, gray mold, etc) and aerosol bacteria enter in polyhouse through doorways and ventilator. Soil borne pathogen (damping off, anthracnose, verticillium wilt and fusarium wilt, etc) enters by adhering to footwear, tools and machinery, aquatic fungi in irrigation water and virus through infected seed or seedling.
Scouting and monitoring: Only early or timely detection and accurate diagnosis is key to reduce/ prevent losses in polyhouse successfully. Scouting help to detection, diagnosis and monitoring to develop management strategies to control insect-pest effectively. Hence, Deep inspection and regular visit is required to detect any disease or insect in cultivating crop. Various signs and symbols are produce by the pathogens/ insects in plant parts which are helpful to detect and diagnose causal agent in cultivating crop visually such as powdery mass, cottony white appearance, white blister, concentric rings, browning of vessels, vein clearing, wilting, drooping of leaves and/or plant, yellowing, dwarfing, thin tunnels, holes in leaf, tinny discolored spot on leaf, upward or downward curling or twisting of leaf / stem. During scouting/ monitoring, both upper and lower surface of leaves should be observed as many insect or disease is also present on lower surface too (eg. Whitefly, aphid, mite, downey mildew etc.).
Other than visual symptompology, techniques are used to diagnosis disease are microscopic study, serological study, PCR based, DNA/RNA probes based, ELISA etc. Generally characteristic symptoms of pathogen/ insect infestation are used to diagnose plant disease /insect by grower. So knowledge of crop behavior and characteristic symptom of disease is very necessary for grower for developing management strategies to prevent/ control diseases and pests.
General Integrated Pest Management (IPM) Strategies in Polyhouse:
Crop specific IPM module has been developed for plant protection in polyhouse but some IPM strategies that should generally follow by grower in polyhouse are as follows:
- Use certified and good quality seeds or planting material.
- Soil sterilization (by busing chemicals as formalin is mostly preferred) should be followed to kept soil free from pathogen after each crop production cycle.
- Healthy disease and insect free seedlings should be transplant (at evening) carefully.
- Clean (1% Chlorine- bleach solution) and sterilized equipment should be used to avoid viral disease as virus is efficiently transmitted by mechanical injury during cultural practices.
- Only person related to crop should be allowed inside the polyhouse.
- Sanitation is must under polyhouse as plant debris harbor pest and disease.
- Regular monitoring (at morning) of the crop and maintaining the climatic conditions under polyhouse is necessary to avoid disease and insect problems.
- Doormat with disinfectant solution should be placed outside of the polyhouse.
- Insect proof screens (50-52 mesh Size) can also be used to prevent the entry of the pests. Screens with a smaller thread diameter are preferred as they are more porous and ventilate better.
- The polyhouse should have double door system which is the safest way to prevent the entry of pests and diseases. The doors should be constructed preferably away from roadside.
- Yellow or blue sticky traps should be used under polyhouse and at entrance door to trap insects.
- Recommended planting space, fertilizer doses, number and amount of irrigation etc. should be followed.
- Overhead sprinkler should be avoid as water film on leaf for longer duration favor the bacterial disease and splashing water drop disperse disease to healthy plant.
- During cultural practices such as pruning, training, staking, thinning should be done with care. Avoid disturbances or damage to plant.
- Soil health should be considered after completion of crop production cycle i.e. nutrient status, physical and chemical properties of soil.
- ETL level should be considered before using insecticide in polyhouse.
- In viral disease, after first appearance of symptom on a plant- Uproot infect plant, use appropriate insecticide and other management practices should be start.
- Special care should be taken when handling disease plant and ensure hands and tools are disinfected before moving to healthy plant.
- It is better to use neem oil under polyhouse at 4 day interval regularly to avoid insect.
- IPM practices such as seed treatment, sanitation, tillage, rouging, crop rotation, use of bio-agents (Trichoderma, Pseudomonas etc.), bio-insecticides and recommended dose of pesticides should be use. In comparison with open field cultivation, pest and disease problems are less in polyhouse cultivation and can be managed efficiently by using specific IPM module for individual crop if problem is accurately diagnosed and management practices is started timely. Hence, regular scouting, proper diagnosis, right management practices are key of success in plant protection under polyhouse cultivation.
1. "Diseases and Management of Crop under Protected Cultivation" Proceeding of 26th training, CAFT in Plant Pathology, G.B. Pant University of Agriculture and Technology. 2012.
2. Sabir, N. IPM and GAP in Protected Cultivation, Doubling Farmers Income through Horticulture. Daya Publishing House, New Delhi. Pp-589-599. 2017.
About Author / Additional Info:
We both have done our master's degree in Plant Pathology and providing our services in Agriculture Private sector