In all natural habitats, plants are surrounded by an enormous number of potential enemies (biotic) and various kinds of abiotic environmental stress, greatly responsible for heavy reduction in crop productivity. To counter the herbivore attack, plants produce defensive compounds that appear to have no direct function in growth and development. These substances are known as secondary metabolites. Secondary metabolites, including terpenes, phenolics and nitrogen (N) containing compounds, defend plants against a variety of insect herbivores. These compounds are either produced constitutively or in response to plant damage, and affect feeding, growth, and survival of herbivores. Many compounds act directly on the herbivore, whereas others act indirectly via the attraction of organisms from other trophic levels that, in turn, protect the plant. The role of secondary metabolites in defense may involve deterrent and anti-feedant activity, toxicity or acting as precursors to physical defense systems. By virtue of their biological activities against insect herbivores, many of these substances are employed commercially as insecticides, while others find uses as fragrances, flavorings, medicinal drugs, and industrial materials.
The Southern Odisha comprising of ten districts accounts for 40 per cent of geographical area and 27 per cent (11.46 million) of the population of the state. The region receives more than 200 mm of rainfall in each month from June to September and in October it receives 121 mm rainfall. The net area sown is 1.93 million ha (36% net area of the state) out of 5.42 million ha in the state. In Southern Odisha, 23.73 lakh ha is under food grain crops which constitute 35% of food grain area in the state (67.56 lakh ha). The region contributes 34.4 lakh t of food grain out of 96.3 lakh t in the state and the region contributes 35.3% of cereal production in the state (85.74 lakh t). The fertilizer consumption in the region is less than state average consumption of 57.1 kg/ha. The net irrigated area of Southern Odisha is 6.5 lakh ha constituting 29% of the state net irrigated area (22.53 lakh ha) and 28% of gross irrigated area in Odisha. Kharif rice occupies 88% of the cereal irrigated area (5.43 lakh ha) and 78% of irrigated area in rabi out of 0.97 lakh ha of cereal irrigated area of rabi in the region. The area under irrigation is less under oil seeds and vegetables. The low crop productivity in the region is due to low soil fertility statuslow in nitrogen and phosphorus, soil acidity/ salinity, imbalanced fertilizer use and micro nutrient deficiency in crops, use of traditional varieties and practices, low rate of seed replacement, indiscriminate use of pesticide and fungicide, lack of knowledge in improved farm implements. Low yield in rice is due to incidence of pest particularly BPH, stem borer and disease sheath blight and blast and poor weed and irrigation management. The strategies for improving the crop productivity include promoting use of appropriate crop varieties, improving the health of soil, more emphasis on resource conservation/ regeneration technology in land and water management, incentivization for irrigation development, land shaping, mechanization, diversification, planning for timely delivery of required production inputs, specifically quality seeds, value addition and putting in place an effective technology transfer system.
Aulacophora foveicollis, a polyphagous pest of more than 81 plant species is known for its voracious feeding habit. Studies on occurrence and population density of this pest were carried out under field conditions at Assam Agricultural University, Jorhat. Correlation studies revealed that population density of A. foveicollis showed significant negative correlation with maximum temperature and significant positive correlation with evening relative humidity. Multiple regression equations were developed for A. foveicollis to predict their seasonal incidence under the agro climatic conditions of Jorhat.
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