DISEASE AND PEST MANAGEMENT IN RICE

Nepal is a small country in the central Himalayan Mountains between India and China. It consists of low tropical plains and central plateaus that rise up to the world’s highest peaks. Rice is by far the most important crop in Nepal and accounts for about 50 percent of the total agricultural area and production in the country. Rice is cultivated almost in all district of Nepal but for country it is also no enough .Every year’s million tons of rice is imported from neighbor country Indian. What’s may be problem? Is country hasn’t enough land for rice cultivation or due to the lack of skilled manpower. The main problem here seen is farmers lose an estimated average of 37% of their rice crop to disease and pest every year. For this timely and accurate diagnosis should be done which reduce losses.

What are the main disease in rice?

Bacterial blight

Bacterial blight is caused by Xanthomonas oryzae pv. oryzae. It causes wilting of seedlings and yellowing and drying of leaves. This disease is most likely to develop in areas that have weeds and stubbles of infected plants. It can occur in both tropical and temperate environments, particularly in irrigated and rainfed lowland areas. Bacterial blight is one of the most serious diseases of rice. The earlier the disease occurs, the higher the yield loss.

Bacterial leaf streak

Bacterial leaf streak is caused by Xanthomonas oryzae pv. oryzicola. Infected plants show browning and drying of leaves. Under severe conditions, this could lead to reduced grain weight due to loss of photosynthetic area. Its occurs in areas with high temperature and high humidity. On the basis of reported case yield loss caused by bacterial leaf streak can range from 8−17% in the wet season, and 1−3 % in the dry season.

Blast

Blast is caused by the fungus Magnaporthe oryzae. It can affect all above ground parts of a rice plant,leaf, collar, node, neck, parts of panicle, and sometimes leaf sheath. It occurs in areas where the low soil moisture, frequent and prolonged periods of rain shower, and cool temperature in the daytime is present. Rice blast is one of the most destructive diseases of rice. A leaf blast infection can kill seedlings or plants up to the tillering stage. At later growth stages, a severe leaf blast infection reduces leaf area for grain fill, reducing grain yield.

Brown spot

Brown spot has been historically largely ignored as one of the most common and most damaging rice diseases. it is a fungal disease that infects the coleoptile, leaves, leaf sheath, panicle branches, glumes, and spikelets. When infection occurs in the seed, unfilled grains or spotted or discolored seeds are formed. The disease can develop in areas with high relative humidity (86−100%) and temperature between 16 and 36°C. It is common in unflooded and nutrient-deficient soil, or in soils that accumulate toxic substances. It causes both quantity and quality losses.

False smut

False smut causes chalkiness of grains which leads to reduction in grain weight. It also reduces seed germination. The disease can occur in areas with high relative humidity (>90%) and temperature ranging from 25−35 ºC. The disease affects the early flowering stage of the rice crop when the ovary is destroyed. The second stage of infection occurs when the spikelet nearly reaches maturity.

How can disease and pest can be managed?

It can be manage in different way but some of the way are given below

• Diseases can be spread between fields or between seasons, after harvest, be sure to clean the harvesting equipment to prevent the spread of infected plants.
• Certified seed is recommended for farmer but if farmer can’t get certified seed, use clean seed that does not have any discolored seeds, weed seeds or other rice varieties mixed in.
• Planting at the same time as the neighboring fields can help to minimize insect, disease, bird, and rat pressure on individual fields.
• High nitrogen can increase susceptibility to certain pests and diseases that is why specific fertilizer recommendations is very important.
• Overuse of pesticide is common among farmers and can actually lead to pest outbreaks. Natural insect enemies of the rice pests are also killed when pesticides are applied and this can lead to an outbreak of other rice insect pests.
• Generally, a rice crop can recover from early damage without affecting yield. The diseases section show the information on specific diseases that require early management.
• Store grain at moisture content below 13-14%, preferably in an airtight container. Clean the grain before storing so it is free of dust, chaff, and excessive broken grains. The storage area should be clean and have a dampproof floor and waterproof walls and roofs.

What are Pets that cause loss of Rice?

Rat

Rats do not like wide, open spaces because they are more vulnerable to attack from predators.They like to hide and burrow in weedy areas near major irrigation canals, in village gardens, and in other non-crop areas which provide good cover.Before planting is the best time to organize community rat control campaigns. These can be done until three weeks after planting.

Insect

In the early stages of the rice crop, several common insects such as the leaffolder, whorl maggot, and armyworms can cause highly visible damage symptoms; however, the damage is rarely enough to reduce yield because the crop can compensate for early damage over the rest of the growing season.

In most cases, insecticides applied in rice fields during the early crop stages to control leaffolders or whorl maggots are unlikely to benefit farmers economically. Instead, they can cause an imbalance in the natural insect population that may lead to pest outbreaks.

Golden Apple Snail( Pomacea canaliculata and Pomacea maculate)

Golden apple snails eat young and emerging rice plants. They cut the rice stem at the base, destroying the whole plant. Snails are able to spread through irrigation canals, natural water distribution pathways, and during flooding events. The golden apple snail is considered a major problem of rice. If no control measure is taken, they can completely destroy 1 m2 of field overnight. This damage could lead to more than 50% yield loss.

Bird

Rice-eating birds chew rice grains, and can cause whitehead or unfilled panicles. They either squeeze the grains during the milky phase, or eat the entire grain once mature. The damage shows a milky white substance covering the grains. Birds become a problem from ripening phase—when the rice plant is already developing and filling in grains—until harvest.