Efficacy of seed treatment with Apron Star 42 WS and foliar application of emulsified neem (Azadirachta indica, A. Juss) seed oil in the control of sorghum (Sorghum bicolar L. Moench) anthracnose in the Sudan savanna of Nigeria

摘要

The efficacy of seed treatment with Apron Star 42WS followed by foliar application of emulsified neem seed oil in controlling sorghum anthracnose caused by Colletotrichum graminicola was evaluated during the 1999 and 2000 cropping seasons. The experiments were laid out in a strip plot design with three replications. The seed treatment formed the main plot factor while three application regimes of the emulsified neem seed oil were assigned to the sub-plots. The results showed that seed treatment with Apron Star 42WS supplemented with foliar sprays of emulsified neem seed oil significantly reduced the incidence and severity of anthracnose compared to the untreated crops in both seasons. At maturity (120 DAS), the combined disease incidence was 22.25% and 33.45% in the treated and untreated crops, respectively, while disease severity for the same period was 17.63% and 26.08% for the treated and untreated crops, respectively. Also three sprays with the emulsified neem seed oil gave significantly lower disease incidence and severity (23.21% and 18.87%, respectively) compared to one spray (26.34% and 20.07%, respectively) and the control (31.95% and 25.54%, respectively). The reduction in the incidence and severity of the disease led to significantly higher grain yield of 1.09t/ha in the treated crops compared to 0.67t/ha in the untreated crops. Similarly, significantly higher straw or stover yield of 5.18t/ha was recorded in the treated crops compared to 3.09t/ha in the untreated crops. Three sprays with emulsified neem seed oil also gave higher grain yield (1.10t/ha) and stover weight (4.61t/ha) compared to one spray (0.75t/ha and 4.05t/ha, respectively) and the untreated crops (0.74t/ha and 3.57t/ha, respectively). Apron Star 42WS which is the latest formulation of metalaxyl as seed treatment in combination with foliar spray of emulsified neem seed oil gave adequate control of anthracnose and increased grain and stover yields of sorghum in the Sudan savanna of Nigeria.