Greenhouse trials of newBacillus thuringiensis isolates for control ofChilo partellus larvae in sorghum |
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| Authors: | Michael Brownbridge |
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| Institution: | (1) The International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya;(2) Present address: Entomology Research Laboratory, University of Vermont, 05405-3400 Burlington, VT, USA |
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| Abstract: | Eight newBacillus thuringiensis Berliner (Bt) isolates originally recovered from different source materials and geographic locations in Kenya were tested againstChilo partellus (Swinhoe) on sorghum grown in a greenhouse. All isolates had been demonstrated previously to be toxic to this pest.Bt strains were cultured in a liquid growth medium and preserved as powders for experimental application. Three-week-old sorghum
plants (4-6 leaves) were artificially infested with 20 neonateC. partellus and sprayed 24 h later withBt suspensions. Non-infested sorghum and infested non-treated sorghum served as the comparative checks within each experimental
trial. Plant development and dead-heart formation were monitored up to harvest; at harvest, grain yield was recorded. In each
replicate trial, all of theBt strains tested reduced plant damage consistently, compared with the infested, non-treated checks. Dead-heart formation was
significantly reduced and grain yields were significantly higher. Three novel isolates, A-3, A-C-2 and M44-2, provided superior
levels of protection throughout. Statistically, there was no difference among these threeBt treatments and the non-infested check in terms of the number of dead-hearts (i.e., non-yielding plants) that formed during the course of the experiment. In the infested, non-treated check plots, dead-hearts
developed in 74.5±10.0% of the plants, compared with only 3.1±1.2% of the non-infested plants, and 3.1 ±1.5%, 6.2±2.0% and
6.2±2.0% of the plants treated with M44-2, A-3 and A-C-2, respectively. At harvest, the weight of grain obtained from the
non-infested control plots was considered to be 100% of the potential yield for each experimental replicate. In the infested,
non-treated controls, only 14±5.6% of the potential yield was realized. When isolates M44-2, A-3 and A-C-2 were applied, proportionate
yields of 83±5.4%, 93±2.3% and 98±1.2%, respectively, were obtained. Results showed that theBt strains selected may have a strategic role to play in the management ofC. partellus, providing applications are timed to target young larvae feeding in the leaf whorl. |
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| Keywords: | Bacillus thuringiensis Bt new isolates Chilo partellus control on sorghum biological control |
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