玉米种植密度对玉米螟发生及赤眼蜂寄生的影响

通过对不同种植密度玉米田内玉米螟、赤眼蜂调查，初步认为，在低种植密度下一、二代玉米螟百株落卵块数、落卵粒数较高，种植密度为45 000株/hm²玉米田的一代玉米螟危害较重。相关分析表明，一、二代百株玉米的落卵块数、落卵粒数、蛀孔数、隧道长度、活虫数及一代卵块寄生率等与种植密度呈负相关；健株数与种植密度呈正相关；穗上折率、穗柄折率、雄穗折率随种植密度增加折率略有增加。玉米不同种植密度对赤眼蜂的自然寄生率影响较小，30 000株/hm²种植密度一代玉米螟的卵块寄生率和卵粒寄生率略高，为44.24%和39.00%；二代玉米螟的卵块寄生率和卵粒寄生率均较高，平均为84.59%和80.84%。

Effects of Maize Planting Density on Occurrence of Asian Corn Borer and Trichogramma Parasitism

Asian corn bore(ACB) and Trichogramma were investigated with diverse maize planting density in a maize field. The results showed that the 100-maize plants egg masses amount and eggs number were relatively high of the 1st and 2nd generation ACB with low planting density. The corn was damaged serious by the 1st-generation ACB in 45 000 plants/ha maize field. In addition, The correlation analysis showed that egg masses amount, eggs number, bored-hole number, hole pass length, alive worm amount per 100-maize plants and the parasitism rate of ACB egg masses were negatively correlated with planting density. Healthy plants number was positively correlated with planting density. The broken-up ear stem rate, the broken-ear handle rate, the broken-tassel rate increased a little as maize planting density increases. The planting density had almost no effect on natural parasitism rate of Trichogramma. There were slightly higher the egg masses parasitism rate(figure 44.24%) and the eggs parasitism rate(figure 39.00%) of the 1st-generation ACB with 30 000 plants/ha than other planting density. Both were very high the egg masses parasitism rate and the eggs parasitism rate of the 2nd-generation ACB with diverse planting density. The average values were 84.59% and 80.84%.