Presentation on theme: "Methods for assessing rodent loss, damage and contamination to rice stored at the household level in Bangladesh Dr Steven R. Belmain and colleagues Natural."— Presentation transcript:
Methods for assessing rodent loss, damage and contamination to rice stored at the household level in Bangladesh Dr Steven R. Belmain and colleagues Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, ME4 4TB, United Kingdom T: +44 1624 883761; F: +44 1634 883379; E: S.R.Belmain@gre.ac.uk
Introduction Measuring post harvest rodent damage has never been easy or accurate Harris, K. and Lindblad, C.J. (1978) Post-harvest grain loss assessment methods. The American Association of Cereal Chemists. Prakash, I. (Ed) (1988) Rodent pest management. Boca Raton, Fl, CRC Press.
Introduction Rodent contamination was obvious in all household rice stores visited. Rodent damage to store structures was widespread. Villagers widely reported that rodents would eat the stored rice during the night.
Methods 8 kg of rice in a basket Placed individually in farmer stores (n = ?) Two-week interval to measure basket weight, and contamination, damaged grains, moisture content to rice in basket and in the farmer’s own rice store
Methods 175 g sub-sample taken, and the droppings categorised by size and shape for the three main species trapped in households Mus musculus Bandicota benegalensis Rattus rattus
Methods Damaged rice measured by taking two lots of 100 rice grains from the 175 g sub-sample, counting number of rodent-damaged grains to obtain a percentage
Methods Trials carried out over five different storage seasons from 2002 to 2005 in four different villages in the District of Comilla
Mean monthly rates of contamination, damage and loss caused by rodents to baskets of rice placed in farmer stores (n=30) in the village of Anandapur
Linear regression of data collected from the mean values of four villages over four months (Jan-04 to Apr-04) comparing temporal changes in rodent damage and weight loss
Loss rate of rice removed from baskets by rodents between sampling periods in the village of Anandapur. Each data point represents the amount of rice removed by rodents every fortnight.
Non-linear regression best-fit model to data generated from the rate loss data calculated from 64 baskets of rice in household grain stores over four months (Jun-04 to Sep-04)
Linear regression of damaged rice in baskets against the damaged rice in the farm store farm = -1.25 + 0.51 * basket, R² = 0.92
Linear regression of rodent droppings in baskets against the rodent droppings in the farm store farm = -2.24 + 0.44 * basket, R² = 0.90
Analysis summary Loss, damage and contamination of rice in basket are correlated Regression of basket vs. farm damage or contamination shows high R values and slopes As we can only calculate a daily loss rate from the basket, the above suggests the loss rate should be similar between basket and farm store
Analysis summary Loss rate from basket does not significantly change over time. This is used to calculate amount of rice lost from the farm store over time
Effect of intensive trapping on the estimated amount of rice eaten by rodents from farmer’s own grain stores, comparing two villages that have been intensively trapping rodents against two villages that have not trapped