HIGHLIGHTS• New oil-based dispersion with a half-life of T. asperellum conidia of 22.5 weeks.• Complete inhibition of P. megakarya on sprayed detached pods.• Enhanced rate and duration of protection on sprayed cacao pods in the field.• 50% of pods protected 3.2 weeks after spraying in the field.• Formulation suitable for the spraying equipment of small-scale cacao producers. GRAPHICAL ABSTRACTFormulated conidia of Trichoderma provide similar or even better protection of cacao pods against black pod disease than a conventional fungicide. ABSTRACTIn African cacao-producing countries, control of cacao black pod disease caused by Phytophthora megakarya is a priority. Introducing biological control agents as part of a P. megakarya control strategy is highly desirable, especially in a perspective of pesticide reduction. Trichoderma species are among the most used biological control agents. In Cameroon, Trichoderma asperellum formulated in wettable powder has produced positive effects against this disease. However, with this type of formulation, shelf-life and persistence of conidia on pods are limited. Our study therefore sought to develop a new T. asperellum formulation that would be more effective and better suited to the conditions of field application by small-scale producers in Cameroon. We selected a soybean oil-based oil dispersion, in which the half-life of the conidia reached 22.5 weeks, versus 5 weeks in Published in : Biological Control (2014), vol. 77, pp. 15-22 Status : Postprint (Author's version) aqueous suspension. Tested on detached pods, the formulation completely inhibited the development of the disease. When sprayed in the field on cacao clones highly sensitive to P. megakarya, the formulation resulted in 90% protection of treated pods after 1 week, and 50% after 3.2 weeks. The formulations exercised a measurable effect for up to 7 weeks, versus 2 weeks in the case of an aqueous conidial suspension and 5 weeks for that of a conventional fungicide (Kocide). Trichoderma asperellum formulated in oil dispersion has therefore great potential for the control of cacao black pod disease with less recourse to synthetic fungicides.

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In order to develop simple and adaptable measures to reduce the impact of changing climatic conditions and poor postharvest practices on grain quality, data on temperature and postharvest practices were collected and correlated with physical grain quality parameters for 3 rice development hubs (Ndop, Lagdo and Mbam) in Cameroon. Inter-annual variations in temperature and thermal amplitudes were the highest in Ndop followed by Mbam and the least in Lagdo. When the same rice variety was grown in the hubs and milled with a laboratory hand dehusker, the mean chalky score was highest in Ndop (18%) and least in Mbam (11%). In addition, Ndop recorded higher grain fissures and broken fractions compared to Mbam or Lagdo. Positive correlations were observed between thermal amplitudes, grain fissures and the proportion of broken fractions. However, rice milled using commercial mills located in the hubs recorded the highest broken fractions in Mbam (54% -63%), followed by Lagdo (43% -52%) and the least in Ndop (35% -38%). The type of mills in the hubs was responsible for these differences as Mbam had only Engelberg types mills that recorded higher broken fractions than in Ndop where only rubber roll mills were present (P < 0.05). Lagdo had a mixture of Engelberg and rubber roll mills and recorded intermediate broken fractions. Proper parboiling, recovery and processing of poorly filled and immature grains during parboiling and processing of low-grade and fine broken rice into product generally accepted by the local population were demonstrated as simple adaptation strategies to mitigate S. A. Ndindeng et al. 179the adverse effects of changing climatic conditions and poor postharvest practices on the physical quality of rice especially in sub-Saharan African countries.

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