Upland Rice Oryza Sativa Research Articles

Early planting and overseeding in the cultural control of rice seedling maggot Atherigona oryzae Malloch in the Philippines

Rice seedling maggot Atherigona oryzae Malloch is a minor pest of upland rice Oryza sativa L. and maize Zea mays L. in the Philippines. Two cultural control methods, early planting and overseeding, were evaluated separately on upland rice in an eroded, high rainfall area in Northern Mindanao. Farmers plant maize ahead of upland rice in separate fields with the onset of the rainy season. Regression analysis from data over six seasons showed on average the first 50% of farmers who planted ahead of their neighbours suffered damage significantly below the 5% deadheart action threshold. When early rice planting relative to one's neighbours was combined with earliness with regard to sowing maize, damage was further reduced. Useful methods for forecasting deadheart incidence 1-2 months ahead of rice planting were developed. The deadheart incidence rate was highly correlated with the amount of rain that fell in February and March as well as with the number of adults collected from bait traps in March or April. Six seeding rates were compared in 20-kg increments from 50 to 150 kg/ha with and without insecticide seed treatment. There was no significant yield response over the seeding rates tested when protected by insecticide, but when untreated, the highest yield occurred at 120 kg seed/ha and the greatest return at 90 kg/ha. Yields declined above the 120 kg/ha level from interplant competition. Rice seedling maggot egg density decreased but the deadheart incidence rate increased with increasing plant densities, both linearly. Perhaps higher plant densities led to greater larval survival and dispersal. Planting rice early is dependent on early maize planting. Planting maize early and following maize within the generation period of rice seedling maggot with rice sown from 90 to 120 kg/ha would be particularly beneficial in years when the rice seedling maggot is predicted to be a high risk.

Impact of Gliricidia sepium and Cassia spectabilis hedgerows on weeds and insect pests of upland rice

Double hedgerows of two leguminous multipurpose trees Gliricidia sepium (Jacq.) Walp. and Cassia spectabilis DC. were established in highly eroded, low organic matter, acid uplands in northern Mindanao, Philippines. Alleyways were grown with upland rice Oryza sativa L. and fertilised with G. sepium green manure or C. spectabilis mulch (or in combination) and assessed for weed and insect pest suppression. Mulch reduced weed biomass which was mostly composed of grasses on infertile soil. Green manure favoured broadleaf weeds and increased weed biomass reducing the effect of mulching. Greater weed suppression may be achieved. Improvement in soil fertility increased the crops’ competitiveness against weeds by concentrating it to crop furrows. Greater crop nutrition from hedgerow biomass resulted in increases of rice seedling maggot Atherigona oryzae Malloch and stem borer (mainly Sesamia inferens (Walker)) damage and white grub (mainly Holotrichia mindanaoana Brenske and Leucopholis irrorata (Chevrolat)) larval densities over the control. Terrace formation reduced white grub densities the first year. The trend reversed in the second year as shade from the hedgerows and mulch probably favoured survival of white grub larvae by reducing soil temperature and increasing soil moisture. Despite higher insect pest densities, the moderate tillering UPLRi5 tolerated weeds and insect pest damage to produce higher yields in the biomass treatments than the control. But hedgerows may increase the incidence of rice blast Pyricularia oryzae Cav. by decreasing air movement. As purchased fertilisers provide limited crop response on depleted soils, alley cropping provides an economical means to overcome that constraint in small-scale tropical agriculture.