Pest of deepwater rice and their management

摘要

Deepwater rice has a distinctive pest complex due to prolonged deep flooding, extended growth duration and a complex environment. Flooding smothers weeds, prevents population buildups of some pests and diseases, and stimulates new growth which may compensate for early damage. Major pest are adapted to these aquatic conditions and exploit the succulent growth and mild weather extremes of this period. In Asia, yellow stem borer causes widespread damage by producing a loss of bearing stems, and lighter or empty panicles. No appropriate measures are known and control of this major pest is a daunting challenge. Stem nematode severely damages rice in several areas but varietal resistance is effective. Rats and hispa beetle are also injurious and many lesser pest are know. In West Africa's smaller Deepwater rice area, stem borers, leafeaters, birds and rats are damaging but their effect on yield is obscure. Farmers commonly employ cultural control methods, and insecticides are used in some areas but diseases are not treated. Pesticide use is restricted by application difficulties, contamination concerns and the low value of the crop. In Asia and Africa wild rices, grasses and sedges compete fiercely with rice before flooding; herbicides are not generally used but many farmers hand weed though the extent of yield loss is poorly understood. Pest management research in deepwater rice is difficult because of the nature of the agroecosystem. Most research has been carried out in Asia but the volume has seriously declined over the last decade.