Assessment of maize (zea mays l.) damage and yield loss due to rodents in the field
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Date
200
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Publisher
Sokoine University of Agriculture
Abstract
Assessment of damage and yield Joss due to rodents was carried out in maize fields in
Morogoro. Tanzania. The most abundant rodents in these fields were the multimammate
rats. Mastomys nalalensis. Spatial distribution of damage in maize fields was random for
experimental fields planted with maize, located between other maize fields owned by
farmers. Four sampling techniques viz: non stratified systematic row sampling, non
stratified systematic z-sampling. stratified random square sampling, and non stratified
simple random sampling for estimation of maize damage and yield losses due to rodents
were compared in terms of precision and accuracy, and time spent for damage and yield
loss estimations. The actual rodent damage in 15 maize fields was determined by
counting damaged and undamaged maize plants at seedling stage and the actual yield
loss was calculated. The actual damage varied from 17.3% to 82% during the period of
study. The results showed clearly that non-stratified systematic row sampling is the most
robust technique for assessing maize damage and yield loss due to rodents. A standard
curve for sampling using this technique is provided. The relationship between rodent
density and maize damage at seedling was determined. The best model for the data was
determined using Akaike Information Criterium. The best model for the relationship is
Sigmoid (r - 0.74; n = 44; p = 0.001). Variations occurred between the observed and
predicted line. Damage was low or high depending on the amount of rainfall after
planting. Maize seed planting followed by heavy rainfall suffered lower damage than
when rainfall was poor, due to inability by rodents to locate the planted seeds. Rodent
damage and the resultant yield loss are positively correlated, but only in years with well distributed rainfall. Results from model simulations showed that it is more profitable to control rodents in the fields in February and November or February and October than any other month combinations. This calendar approach for rodent control seems to be most appropriate for the Tanzanian maize growers.
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Keywords
Maize, Zea mays l., Yield loss, Rodents, Maize damage, Crop damage, Pest control