Biocontrol Agents and Diatomaceous Earth

An excerpt from:

Chapter 6

EFFECT OF BACILLUS THURINGIENSIS (BERLINER), CLONOSTACHYS ROSEA (SCHROERS) AND DIATOMACEOUS EARTH ON SHEEP NEMATODES: FEEDING TRIAL

M.A. Baloyi and M.D. Laing

Discipline of Plant Pathology,
School of Agricultural Sciences and Agribusiness
University of KwaZulu-Natal
March 2011

Abstract

The ability of biocontrol agents and diatomaceous earth (DE) to reduce the number of nematode counts was evaluated in adults and lambs of Merino sheep. The sheep were naturally infected with a mixed culture of gastrointestinal nematodes, primarily Haemonchus contortus. A selected strain of C. rosea (9AB8) was grown on barley grains. The spores of a selected strain of Bt (AB2) were grown on the wheat barn. The cultures of Bt and C, rosea, together with a commercial formulation of DE were mixed with a complete diet and fed once daily to the sheep according to their individual body weights. Results indicate that there was a significant effect of treatments on the body weight gain of sheep (P = 0.032). Treatment of Bt 1g kg^-1 BW, Bt 2g kg^-1 BW, and DE resulted in body weight gain of 34.3, 35, and 32kg, respectively. C. rosea showed a lower body weight gain of 26.2 kg and was outperformed by the Control (30.7 kg). There was no significant effect of treatments on egg per gram (EPG) (P= 0.440). Treatments significantly reduced larvae per gram (LPG) counts (p<0.001). Treatments had mean LPG counts of 55,59,34 and 69 for Bt1g kg^-1 BW, Bt 2g kg^-1 BW, C. rosea and DE, respectively. Control group had a mean LPG of 423. The mortality of L3 after application of treatment were 74.6%, 75.1%, 84,6%, 68.5% and 27.5% for, Bt 1g kg^-1 BW, Bt 2g kg^-1 BW, C. rosea, DE and the Control group, respectively. Daily feeding of BCAs to sheep was effective in reducing the numbers of L3 larval stages.