双穗雀稗—空心莲子草杂草群落对稻田节肢动物、水稻产量的影响及其防除经济阈值

Effects of Paspalum paspaloides-Alternanthera philoxcroides weed community on arthropods and rice yield and the economic threshold

通过田间试验和调查对上海郊区稻田双穗雀稗-空心莲子草杂草群落和节肢动物、水稻产量关系进行了研究,构建了双穗雀稗-空心莲子草杂草鲜重与昆虫发生量、水稻产量、每穗实粒数、有效穗数、白穗数等指标之间的回归方程。结果表明:随着杂草群落生物量的增加,因水稻穗数、每穗粒数减少会极显著地降低水稻的产量;因同翅目、双翅目等昆虫数增加会极显著地增加稻田昆虫的发生量;虽增加了稻田昆虫的多样性,并使某些优势昆虫发生加大,但并没有增加有益动物蜘蛛的数量。杂草群落竞争性利用环境资源,并诱发昆虫、白穗等病虫害的发生而使水稻产量下降。多元线性回归分析表明:双穗雀稗和空心莲子草是引起水稻产量下降的主要原因,昆虫的发生更多是由双穗雀稗引起的。根据经济危害允许损失率计算公式,得出移栽稻田双穗雀稗和空心莲子草杂草的防除经济阈值为21g/m^2。

The relations between Paspalum paspaloides-Alternanthera philoxeroides weed communi- ty in rice fields of Shanghai suburbs,arthropods and rice yield were studied through field experiments and survey, and regression equations were established between the fresh weight of weeds and the insect quantities, rice yield, filled grains per spike, effective spikes and white heads. The results showed that with the weed biomass increasing,the rice yield decreased very significantly due to decreasing of the effective spikes and filled grains per spike;the insect quantities increased very significantly owing to increasing of the homopteran and dipteral insects;and increasing of the insectean diversity made some dominant insects occur largely but the quantity of beneficial spiders did not increase. The weed com- munity competitively utilized the environmental resources and caused disease and insect pests to hap- pen,thus making the rice yield decrease. The multiple linear regression analysis revealed that P. pas- paloides and A. philoxeroides were a major factor influencing the rice yield,and the increase of the in- sect quantities was caused mainly by the biomass increase of P. paspaloides. In the transplanted rice filed where P. paspaloides and A. philoxeroides were dominant weeds, the economic threshold for controlling the weeds was 21 g/m2.