數種殺蟲劑對甘藍蚜蟲和小菜蛾防治試驗

Abstract

供誠數種殺蟲劑中，以Padan 50% SP 1250倍及Salithion 25% EC 500倍，對蚜蟲類和小菜蛾之防除，均有優異效果，較標準殺蟲劑大利農（Diazinon）雖略差些，但差異並不顯著。 Gardona 24% EC500倍，對小菜蛾防除效果雖佳，但對蚜蟲煩，尤以菜蚜Breoicoryne brassicae卻完全無效，在其試用期間，蚜蟲之為害率，自始至終與對照區者甚相近似。 Lanoate 90% WP之1500倍液，對蚜蟲類和小菜蛾，雖亦有優異防除效果，但因對包心白菜和甘藍均相繼發生藥害。其藥害程度，因濃變高低，施藥次數及施藥集量多寡而有嚴重和輕微之差，並隨蔬菜屋煩不同而異，一般包心白菜較甘藍容易發生藥害。 數種除蟲效果較優殺蟲劑，對蔬菜產量亦有提高效果。除Lannate和Gardona外，Salthion, Diazinon, Dibrom和Padan等四種殺蟲劑處理區與對照區相比，均增產甚多。 Padan 50% SP, Gardona 24% EC, Lannate 90 % EC and Salithion 25% EC were tested against the insect pests, Lipaphis erysimi, Byevicoryne byassicae, Mzus persicae, and Ptiztella macuilpennis, on cabbages. Two standard insecticides, Dibrom 64.5% EC and Diazinon 60% EC, and untreated check plots were used in each replication for comparison with the new test insecticides., The criterion of evaluation is based on the reduction of insect population, phytotoxicity, and crop yields. All of the insecticides were applied five times starting from the time about eight days after planting at ten days intervals. Insect popnlations were estimated nine days after each application. Aphid infestations were made on percentage of leaves infested with the three kinds of aphids mentioned above. Diamondback moth damage was determined by counting the larvae present on five leaves of each examined plant after the first application, while ten leaves were examined after the second application and other following applications. Padan 0.04% and Salithion 0.05% were highly effective against these three kinds of aphids as well as diamondback moth. Gardona 0.048% was excellent against diamondback moth but failed in controlling aphids. The percentage of aphid infestations on Gardona treatment was similar to that of untreated cheek. Lannate 0.06% gave effective control for both aphids and diamondback moth, but serious phytotoxicity appeared on cabbages after three or four applications were made. More serious phytotoxicity caused by Lannate was also observed on chinese cabbages in another trial. The symptom of phytotoxicity caused by Lannate on chinese cabbage is very similar to the symptom caused by downy mildew (Peronospera brassicac Gaum). But it can be distinguished by examining the undersurface of leaves. If it is caused by Lannate, the undersurface of leaves is smooth and shining, while it is caused by downy mildew is covered by lots of conidia and conidiophores. As the check insecticides, Diazinon 0.04% showed better result against both aphid and djamndback moth than Dibrom 0.0645%. Yields of cabbages were significantly increased both in quantity and quality in the treated block which showed excellent results of insect control. There is something worth to be mentioned that aphid populations were greatly affected by weather conditions. As showed in table I, the populations of aphids dropped clown sharply during the second and third examinations. It was due mainly to the fact of a cold stream came with light rainfall in the early of February for several days in southern Taiwan. The average minimum temperature dropped to 11.4℃ during that time, when the cold stream passed away and the average minimum temperature raised to 14℃ and higher, the population of aphids increased greatly again in the fourth examination.