Sensibility to Mononychellus tanajoa Bondar (Acari: Tetranychidae) of some cassava (Manihot esculenta Crantz) cultivars and effect of damage on yield loss in the Cameroonian Western highlands
2001
Badegana, A.M. (Universite de Dschang (Cameroon). Faculte d'Agronomie et des Sciences agricoles. Dept. de protection des vegetaux) | Mborohoul, J.B. | Alzouma, I.
The study of the sensibility to the green mite Mononychellus tanajoa Bondar of some cassava (Manihot esculenta Crantz) cultivars and the assessment of the effect of damage on the yield losses was carried out in the Western highlands of Cameroon. Four cassava cultivars were used: two local (Dschang and Njombe) and two improved varieties (IITA 8017 and IITA 82516). The results showed that the density (mites number per square centimenter of leaf area) was low during the rainy season and high during the dry season, which means that rains reduce the mite population by washing or lead the mites to death. The highest mean density (3.40 mites per square centimenter of leaf area) was obtained on the local Njombe cultivar which is consequently the most sensitive. On the contrary, the local Dschang cultivar, with the lowest mite density (1.40 mites per square centimenter of leaf area) was the most resistant followed by the IITA 8017 cultivar (1.74 mites per square centimenter). The IITA 82516 cultivar had a mean density of 2.65 mites per square centimenter. Yield losses ranged from 36.90 / for IITA 8017 (1.74 mites per square centimenter and damages level of 2.75) to 58.70 / for local Dschang (3.40 mites per square centimenter and damages level of 3.84). Local Dschang cultivar (1.40 mites per square centimenter and damage level of 2.96) and IITA 82516 (2.65 mites per square centimenter and damage level of 2.96) had a yield losse of 38.10 / and 41.80 /. The results showed that higher the mite density and damage level are, higher is the yield loss, unless the cultivar is tolerant.
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