Rodent Damage and Burrowing Characteristics in Bangladesh Wheat Fields

Abstract

Rat damage to wheat was assessed in 303 fields (196 ha) in 4 districts of Bangladesh. In an appraisal of 315,000 wheat stems, only 0.5% were cut by rats before the booting growth stage. The countrywide rat-damage estimate in mature wheat was 12.1%, or 77,000 tons of grain destroyed before harvest. Wheat damage is attributable primarily to the lesser bandicoot rat (Bandicota bengalensis). Damage was highly correlated with stem density. Yield loss and percent rodent damage were also correlated. The average yield for 20 fields was 1,795.9 kg/ha. Seventeen percent of the damaged stems had only the panicle removed, whereas 83% were cut near ground level. Twenty lesser bandicoot rat burrow systems were excavated from the centers of wheat fields. The mean burrow length was 40.2 m, and storage chambers contained as much as 18 kg of cached wheat panicles. Rat damage was correlated with the number of active burrow systems within fields. J. WILDL. MANAGE. 46(1):139-147 Various vertebrate pest species cause serious crop losses throughout southern Asia, and rodent infestations are a major problem in most field crops. The principal pest rodents in Bangladesh wheat fields are burrowing Muridae, primarily the lesser bandicoot rat (pers. observ.). In addition to what it consumes during the growing season, the rodent digs elaborate underground burrow systems and caches large amounts of grain. Although many farmers complain of considerable loss of rice and wheat in their fields, the present study provides the first information on the magnitude and extent of the losses in Bangladesh. Wheat production in Bangladesh is becoming increasingly popular among farmers. Between the 1977-78 and 197879 crop seasons, the area under cultivation increased from 150,000 to 291,000 ha. The traditional dry-season Boro rice crop (Jan-May) is much more difficult to cultivate because it requires frequent irrigation, most of which is done by hand. Wheat requires little cultivation and watering after broadcasting. Yields over the last 4 years have increased from an average of 1.431 to 1.939 tons/ha, reflecting promotion of adaptable high-yielding varieties. The objectives of this study were to quantify the extent of rodent damage in wheat, identify which rodent species were causing most of the damage, and determine the effects of stem cutting on yield. The stem is defined as that portion of the plant that gives rise to a panicle (i.e., seed head). Existing methods for damage assessments in wheat are few; however, Bindra and Sagar (1968) examined wheat losses in India, and Khokhar et al. (unpubl. rep., FAO-Vertebr. Pest Centre Working Pap. PAK/71/554, 1979) conducted similar studies in Pakistan. Support for this study was provided by the Bangladesh Research Institute and the U.S. Agency for International Development project Agricultural Research, Vertebrate Pest Component, PASA ID/BNG-0003-1-78. A. Mannan I, A. Mannan II, D. Miah, and J. Libay assisted in various aspects of the fieldwork. M. Fall offered comments on earlier J. Wildl. Manage. 46(1):1982 139 This content downloaded from 157.55.39.253 on Sat, 11 Jun 2016 05:26:12 UTC All use subject to http://about.jstor.org/terms 140 RODENT DAMAGE IN BANGLADESH* Poche et al.