Effect of fertilizer levels on population of sucking insects, predatory spiders, and damage caused by stem borer in wheat no. 1015
1987
Kanok Uraisakun | Pramot Phonsuriya | Sirinun Aemprapa
Number of insects found were higher in fertilized plot than in non-fertilized one. It increased in accordance with the amount of fertilizer applied. It declined at certain level of fertilizer, but was still higher than in non-fertilized plot. The infestation on wheat was severe, as observed from considerable leaf damage, at 1.5-3 month old stage after which severity was reducing. The maximum number of insects was 320 for fertilizer rate of 60-40-0 plot (yield gained of 396 kg/rai) and 310 for non-fertilized one (yield gained of 310 kg/rai) less of sucking insects were found in non nitrogen or phosphate fertilized. The influence of insects on yield (r2) was 30.25. However that of predatory spiders on sucking insect was 3.6 (r2). The wheat that showed whitehead symptom were collected and counted on the 30th day before harvesting for every subplot. The maximum number of whitehead were found in plot which used only phosphate (P2O5) (0-40-0). It was significantly different from the non-fertilized one (LSD 0.05), but the number of whitehead from non-fertilized plot was not significantly different from any other treatments. The smallest number of whitehead was found in fertilizer rate of 90-40-0 plot which had maximum yield (411 kg/rai). The influence of the number of whitehead on yield was also explained by determined correlation coefficient (r2=0.0038) ie. High yield plot had a tendency to have less whitehead. The average number of whitehead was significant at 95 % level and the C.V. of 4.32 %.
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