Effect of a Biopesticide base on calcium, Azadirachta indica A. Juss, Sida acuta Burm. F. and Cymbopogon citratus on cocoa (Theobroma cacao) seedling production

Biopesticides are a useful and a promising alternative to the synthetic chemical pesticides use in agriculture to fight against parasites and diseases. The aim of this study was to evaluate de effect of a bioformulation base on neem (Azadirachta Indica A. Juss.), tough weed (Sida acuta Burm F.) citronella (Cymbopogon citrates) and calcium in cocoa (Theobroma cacao L.) seedling production in greenhouse. Stability (physically and thermodynamically) and bioactivity (fungicidal) of the biformulation were determinate. Action mode on Phytophthora megakarya and tolerance by cocoa were also determinate. Therefore, effect of the foliar application of the bioformulation (at 1%) on seedling production was determined and it effect on black pod diseases and cocoa resistance were evaluated on detached leaves. The bioformulation was 100% of stability at 25°C and unstable when subject at -20°C, 45°C or by centrifugation at 25°C 1000g and characterized by a flocculation of the cream; oil; and precipitation and cream flocculation respectively. For a concentration less than 1%, it does not have a negative effect on cocoa leaves. The bioformulation has a dose dependant activity (P ≤ 0.05) against plant pathogens with 100% of inhibition at 1% on Fusarium oxysporum, pythium myriotylum, Phytophthora infestans and Phytophthora megakarya; at 0.1%, we have 55.88±1.65% of inhibition on Phytophthora megakarya and biopesticide act by a lytics and proteins synthesis inhibition on this cocoa pathogen. In addition, treatment of cocoa increase significantly leaves area by 15% and help very susceptible leaves to be resistant by by increasing at least 22% (P≤0.05) the amount of protein, phenolic compounds, peroxydases and β-1,3-glucanases before and after infection. These results suggest that, our bioformulation can be useful for plant protection and cocoa seedling production specially for an sustainable agriculture.
Key words: Biopesticide, action mode, cocoa seedling, Phytophthora megakarya.