Incidences And Spatial Distribution Of Stem Borers In Rice Crop In Kahama District

ABSTRACT

Studies were carried out to establish the role and significance of rice stem borers as pests in rice crop in Kahama District from November, 2013 to May, 2014. Twenty rice fields in four wards of Kahama District were surveyed to assess the presence of larvae and adult moths. Each field was divided into four strata within which four quadrats were established in each. In each quadrat, the damaged rice tillers (dead heart), damaged panicles (white head) and total number of tillers and panicles were counted. Stem borer incidences were computed from observations for each of the studied rice varieties and with reference to the sowing dates. Stem borer larvae were extracted from each of the damaged tiller and counted to establish stem borer dispersion. Moths were trapped by a black light trap cascaded with normal light attached to a white cloth and collected in vials for further identification in the laboratory. Dispersion was determined by three indices i.e. Morisista’s index, Taylor power law and Iwao’s mean crowding regression. Statistical packages (GenStat 15 edition VSN international) and (SPSS 16 version IBM Corporation) were used for data analysis of abundance and incidences respectively. Results indicated that the most abundant species was Chilo partellus (48.6%) followed by Maliarpha separatalla (35.4%) and lastly Sesamia calamists (16.1%). Dispersion indices suggested that borers were highly aggregated along the edges of rice fields compared to the middle of fields. Behenge and Supa varieties were more susceptible to stem borer damage than Kalamata and Mayobhe. The best sowing date with minimum stem borer damage was from 1 to 20, December. The current study has for the first time confirmed the presence and significance of rice stem borers in the lake zone of

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Tanzania that calls for intensive intervention program to ensure farmers of continued food security and livelihood.