잎브로콜리에 심각한 피해를 주는 배추좀나방의 적절한 방제시기 설정을 위한 기초자료로 이용하기 위하여 유충접종밀도와 잎브로콜리 피 해량의 관계를 분석하여 경제적피해허용수준과 요방제 수준을 설정한 결과는 다음과 같다. 배추좀나방 3~4령 유충을 주당 0, 0.5, 1.0, 1.5, 2.0 마리를 5월 24일에 접종하고, 6월 1일, 6월 9일, 6월 18일에 발생밀도와 엽수량을 조사한 결과, 초기 접종밀도가 증가할수록 배추좀나방의 발생 밀도는 증가하였고 시간이 경과할수록 엽수량은 감소하였다. 이를 토대로 배추좀나방의 접종밀도와 수량감소율을 회귀식을 이용하여 분석한 결 과 y=1636-394x (R 2 =0.79***)로 추정되었다. 잎브로콜리에서 5% 피해율을 경제적 피해한도로 볼 때 배추좀나방의 경제적피해허용수준은 10 주당 2~3마리이고, 요방제 수준은 10주당 1-2마리 수준으로 추정된다.

This study was conducted to develop the economic threshold for the diamondback moth (Plutella xylostella (L.) on Leaf Broccoli (leaf vegetable) in 2007. To investigate the relationship between initial density of diamondback moth larvae and broccoli leaf yield, experimental plots with five treatments (0, 0.5, 1.0, 2.0, 4.0 larvae per plant) as initial density were established. We inoculated larvae in chesses cloth covering to survey larvae density change. When grown to eat, leaves of broccoli were harvested by periods. 60-70% of larvae were removed whenever we picked the leaves. High levels of larvae were associated with significant reductions in leaf yield. There were 85%, 64%, 58%, and 56% yield reductions from the diamond back moth larvae density in 0, 0.5, 1,0, 1.5, 2.0 per plant, respectively 25days after larvae inoculation. The regression equation used to predict leaf yield based on the number of initial larvae density per a plant was y=1635-393x(R2=0.79***). The economic injury level of diamondback moth on leaf broccoli was 2-3 larvae per 10 plants for a damage level of 5%. The economic thresholds was 1-2 larvae per 10 plants. Thus, the diamond back moth management should be initiated 1-2 larvae occurrence per plant.