disease symptoms were evident. The type of extract
and time of application a!ected the spread of blast disease
to other plant tissues. Oil extract signi"cantly reduced
the spread of the disease 2 d after arti"cial
inoculation and when the disease was evident compared
with carbendazim at 0.1% a.i. However, both treatments
A.C. Amadioha / Crop Protection 19 (2000) 287}290 289
completely checked the spread of the disease 2 d before
inoculation.
Results from this study indicate the presence of fungitoxic
substances in the di!erent extracts of neem which
is in agreement with the report of workers on di!erent
plants and pathogens (Amadioha, 1998; Amadioha and
Obi, 1998; Qasem and Abu-Blan, 1996; Annapurna et al.,
1983). Maximum radial growth reduction and checking
of spread of blast disease in rice by P. oryzae by di!erent
extracts of A. indica is established in the following ascending
order; hot water leaf extract, cold water leaf
extract, alcohol leaf extract, and seed oil extract treatments
respectively. The di!erence in the toxicity of the
di!erent extracts may be due to the solubility of the
active compound(s) in the solvents or to the presence of
inhibitors to the fungitoxic principle (Tewari and Nayak,
1991; Qasem and Abu-Blan, 1996; Amadioha and Obi,
1998). However, the presence of the active component in
plants is in#uenced by several factors such as method of
extraction, age of the plant, time of harvesting plant
material and di!erent extracting solvents (Nicolls, 1969;
Qasem and Abu-Blan, 1996).
The greatest reduction in the incidences and severity of
blast disease was observed in rice plants treated with the
extracts 2 d before inoculation with P. oryzae suggesting
that the extracts would be more e!ective when applied
preventively as opposed to curatively.
disease symptoms were evident. The type of extractand time of application a!ected the spread of blast diseaseto other plant tissues. Oil extract signi"cantly reducedthe spread of the disease 2 d after arti"cialinoculation and when the disease was evident comparedwith carbendazim at 0.1% a.i. However, both treatmentsA.C. Amadioha / Crop Protection 19 (2000) 287}290 289completely checked the spread of the disease 2 d beforeinoculation.Results from this study indicate the presence of fungitoxicsubstances in the di!erent extracts of neem whichis in agreement with the report of workers on di!erentplants and pathogens (Amadioha, 1998; Amadioha andObi, 1998; Qasem and Abu-Blan, 1996; Annapurna et al.,1983). Maximum radial growth reduction and checkingof spread of blast disease in rice by P. oryzae by di!erentextracts of A. indica is established in the following ascendingorder; hot water leaf extract, cold water leafextract, alcohol leaf extract, and seed oil extract treatmentsrespectively. The di!erence in the toxicity of thedi!erent extracts may be due to the solubility of theactive compound(s) in the solvents or to the presence ofinhibitors to the fungitoxic principle (Tewari and Nayak,1991; Qasem and Abu-Blan, 1996; Amadioha and Obi,1998). However, the presence of the active component inplants is in#uenced by several factors such as method ofextraction, age of the plant, time of harvesting plantวัสดุและ di ! ระหว่างการผลิตสกัดตัวทำละลาย (Nicolls, 1969Qasem และอบูบลาน 1996)การลดอุบัติการณ์และความรุนแรงของบรรดาโรคระเบิดพบว่า ในพืชข้าวที่รับการรักษาด้วยการแยก 2 d ก่อนกักบริเวณกับ P. oryzae แนะนำว่า สารสกัดจะเติม e ! ective เมื่อใช้preventively เมื่อเทียบกับ curatively
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