DAMAGES CAUSED BY COTTON RAT, Sigmodon hispidus zanjonensis, ON SUGAR CANE IN SAN PEDRO SULA, HONDURAS

Technical assistance was given to Compañía Azucarera Hondureña, S.A. (Agro-Industrial Co.), Honduras, Central America, to determine if a campaign against noxious rodents to agriculture crops was needed. Several trappings were carried out at different places using snap traps to determine the population structure of rodents associated with the crop, and live traps to determine the index or density of the Sigmodon hispidus rat population, which was identified as being responsible for the damage to sugarcane. Results were 43.24% adult males, 14.86% young males, 31.41% adult females, and 10.47% young females. Of the adult females captured, 54.83% were pregnant with an average of 3 to 4 embryos per rat. A control demonstration combat was carried out at one of the experimental stations with a bait prepared with 2% zinc phosphide in a place where it had been previously determined there was a population of 39 rats per hectare. After such control, the population was reduced to 18 rats per hectare, which represents an efficiency of 53.85%. An evaluation of damages was also measured at different places to determine the degree of loss caused by the rats, which proved to be 22.79% damage. The size of the sample was estimated in 3 samples per hectare, with a level of confidence of 95%. INTRODUCTION This work was carried out in January 1977 with technical advice from biologists, of Rodents National Campaign of Direction General of Plant Protection of the Ministry of Agriculture and Hydraulic Resources, to the sugar mills called Compañia Azucarera Hondureña, S.A., in San Pedro Sula, Honduras, CA. The aim of the technical advice was to present the basic points for establishing a campaign against rodents. The first data concerning rat damages on sugarcane crops were collected from the cultivated area that serves the sugar mills. First, in 1964, these damages were very small, but they gradually increased and action was taken to apply chemical control consisting of thalium sulfate or warfarin applications. In 1974, rodent populations had increased considerably but were controlled satisfactorily. In 1976, the sugarcane production was in danger because of the increased rodent populations, especially in regions where crops were not harvested on time; then warfarin and zinc phosphide were applied for control but without any success. The major damage caused by rats was found to be in the stems of sugarcane; based on this point, several surveys or studies were conducted to determine population structure, methods of control, and to evaluate damage. GENERAL DESCRIPTION OF THE SURVEY AREA The sugar mill Compañia Azucarera Hondureña, S.A. is located 15 km NE San Pedro Sula and 12 km West Santa Matilde sugar mills; the region is characterized by a high rainfall annual average estimated at 1,510.84 mm, and the most humid months of the year are generally September and October. It was on San Jose property that the rodent control project was started. MATERIALS AND METHODS In order to know some aspects concerning the biology of rats that damage sugarcane, 9 samplings were carried out using snap traps which were placed in a transect around the different lots. The information obtained enabled us to find out the associated species, the most important ones, and the population structure of the species identified as harmful to the crop. A test control had been applied in an area of 7.21 ha. using zinc phosphide; the rodent population was estimated before and after the poison application. During the sampling, Sherman live traps were used to catch animals; they were placed in net formation to cover an area of 1 ha. We used the catching and marking methods of Lincoln and Petersen. Before the beginning of the test control, acceptance trials of different bait compositions were conducted using the formulation of the sugar mills and another one suggested by the biologist team, as follows: