Studies on the Role of Insects in Cotton Boll Black Rot Occurrence

Abstract

The causal organism of cotton boll black rot can be transmitted by the spiny boll-worm, pink bollworm, and cotton stainer at a very high percentage. More than 42% to 100% infection of the disease is caused by feedings of these insects sprayed with spore suspension. High humidity is another factor favorable to the disease development regardless of insect transmission or artificial inoculation.

本研究之目的在究明一些常見的棉鈴害蟲如金鋼鑽，紅鈴蟲及赤星樁象等之害對棉鈴黑化病病原菌之傳播及侵染媒介情形。本研究分室內試驗與溫室試驗進行之。室內試驗，先使害蟲黏附病原菌孢子後，置二頭同類害蟲於一瓶蓋下黏附在健全棉鈴上，在28℃定溫下任其蛀食4日，再取去瓶蓋及蟲體，并改套塑膠袋；觀測棉鈴黑化病之發生率。溫室試驗則改在棉株上利用銅網代替瓶蓋；固定處理後之昆蟲在一定棉鈴上，4日後取去蟲體并將半數供試棉鈴改套塑膠袋；相互比較黑化病之發生情形。 本研究結果證實處理過棉鈴黑化病病原菌分生孢子之金鋼鑽，紅鈴蟲及赤星樁象在棉鈴上蛀食後可使42~100%之棉鈴發生黑化病。三種供試害蟲中咀嚼式口器害蟲（金鋼鑽及紅鈴蟲）對棉鈴黑化病之傳播比刺吸式口器害蟲（赤星樁象）容易。高濕度對病原菌侵染後之病勢進展有利。供試三種昆蟲之傳播黑化病順序為金鋼鑽，紅鈴蟲，赤星樁象。