A comparison of the toxicity of pirimiphos-methyl and malathion to Typhaea stercorea (L.) when applied to stored maize

The toxicity of freshly applied and aged residues of pirimiphos-methyl and malathion were assessed against adult Typhaea stercorea (L.). Maize was treated with each pesticide at doses of 2, 4, 6, and 8 mg kg⁻¹ and stored at a constant 25 °C and 70% r.h. for 12 weeks. All fresh deposits of pirimiphos-methyl produced 100% mortality as did malathion at 4, 6 and 8 mg kg⁻¹. After four weeks storage pirimiphos-methyl still gave 100% mortality at 6 and 8 mg kg⁻¹ but this dropped to 96% at 4 mg kg⁻¹ and 60% at 2 mg kg⁻¹, while mortality for malathion was less than 31% even at 8 mg kg⁻¹. After 12 weeks storage only pirimiphos-methyl gave effective control with 78% mortality at the highest dose of 8 mg kg⁻¹, while control by malathion had completely broken down. The effect of exposure time on T. stercorea for both pesticides at a single dose of 4 mg kg⁻¹ was also assessed. Beetles were left in contact with treated maize for 2, 4, 6, 8 and 10 d. Fresh and four-week-old pirimiphos-methyl residues produced over 98% mortality at all exposure periods but on 12-week-old residues mortality had dropped and was only 61% following 10 d exposure. Only freshly applied malathion gave 100% mortality and even the maximum exposure of 10 d only produced 51% mortality of T. stercorea at four weeks and 39% at 12 weeks.     

温湿度对毛蕈甲生长发育的影响

本文研究了温度和相对湿度对毛蕈甲(Typhaea stercorea (L.)从卵至成虫羽化各虫态生长发育的影响。在相对湿度为90％时,毛蕈甲的适宜生长发育温度为25～35℃。最适温度为27.5～32.5℃。在30.5℃的条件下,适宜相对湿度为80～90％。对各虫态而言,在适生条件下,温湿度的增加将使各虫态历期缩短,幼虫龄数减少,但对卵的孵化率、幼虫的化蛹率以及蛹的羽化率影响不大。温度低于15℃和高于40℃时,卵不能正常孵化。在16.8～20℃和37.5～40℃的温区内,以及相对湿度低于60％时,毛蕈甲的生存率很低。     

锈赤扁谷盗等3种菌食性储粮害虫的发生分布调查

在中国主要储粮生态区的海南、广东、云南、福建、浙江、湖南、湖北、河南、山东、辽宁、山西和黑龙江等12个省77个地市,现场采集调查了具有代表性的粮库、小麦粉厂、米厂、饲料加工厂和农户等共计505个。在所有调查的12个省内均有米扁虫和锈赤扁谷盗分布发生,除湖南省、山西省和黑龙江省外其余各调查省份均采集到小蕈甲。从发现害虫的单位总个数与调查单位的总个数之比(发现比率)看,米扁虫、小蕈甲和锈赤扁谷盗的发现比率分别为18.81%、11.48%、45.94%,锈赤扁谷盗的发现比率远高于米扁虫和小蕈甲的发现比率。比较不同省份中调查害虫分布发生的广泛性可看出,在海南省调查锈赤扁谷盗的发现比率与米扁虫和小蕈甲的发现比率相似,在山东省锈赤扁谷盗的发现比率略低于米扁虫发现比率,在黑龙江省的锈赤扁谷盗发现比率与米扁虫发现比率一致,其他所调查诸省份中锈赤扁谷盗的发现比率(14.29%～69.81%)显著高于米扁虫(3.03%～36.17%)和小蕈甲(0～33.92%),在我国主要储粮生态区多数省份中锈赤扁谷盗的分布发生程度远大于米扁虫和小蕈甲。