Management of Rats as Pests of Sugarcane
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~anagementof Rats i s ~ e s bof' Sugarcane (iGZ~n
Eighteen species of rodents (rats, squirrels) are pests in agriculture, horticulture, forestry, animal and human dwellings and rural and urban storage facilities in India.Their habitat, distribution, abundance and economic significance vary in different crops, seasons and geographical regions of the country. Among the different rat species, Bandicota bengalensis is the most predominant and widespread pest of agfwlture in wet and irrigated soils as well as in houses and godowns. In dry land agriculture, Tatera indica and Meriones hurrianae are the predominant rat pests. Some species like Rattus meltada,Mus rnusculusand Mus booduga occur in both wet and drylands.
( Natureand extent of damaae The predominant rat species that inflict damage to sugarcane are Bandicota bengalensis, Rattus meltada, Tatera indica and Mus rnusculus. They begin to damage the canes around 90 days after planting and the damage increases with the age of the crop. Damage is mainly caused by gnawing through the rind of the lower internodes of canes and by damage to the roots during digging of burrows by rats, particularly the highly fossorial B. bengalensis.As a result of gnawing of roots and loosening of soil during burrowing, canes may lodge when irrigated or due to wind if not properly wrapped and propped. Lodged canes and ratoon crops are generally known to suffer greater damage. Rats have been reported to partially damage 8.6% - 12.1% canes with most of the damage restricted to lower internodes.These canes weighed about 31.5% less than healthy canes and also contained about 24.5% less sugar content. Compared to other crops the cane fields harbour higher rat populations because they provide an undisturbed habitat for their burrowing, feeding and breeding activities, a protective cover from avian predators and an abundant amount of high energy food for most of the year. In addition to the resident population of rats, frequent waves of immigration from surrounding fields as a result of disturbance caused by ploughing, harvesting and flooding with irrigation or rainfall often enhance rodent population in cane fields.
(-*urns Due to variations in geographical and climatic factors, systems of crop production and post-harvest storage, biology of the pest species, the nature and extent of problems caused by the rats, and the perceptions and socioeconomic conditions of the people, no single strategy or method of control is feasible or applicable under different situations. The available management options can be grouped into two basic approaches: non-lethal or ~ r e v e n t i v e and lethal or redictional. The non-lethal or preventive measures involve environmental, cultural and more lasting effect. However, the lethal approach, particularly the use of rodenticides and trapping, which provides an immediate solution to the problem, is often considered the most practical, econom~cal and effectlve methodof combating rats.
Environmental I methods
1 Damaged canes
and cultural
A clean environment, particularly removal of wild vegetation or weeds, discouraqes rodents from establishing in an area
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Mechanizationof agriculture also reduces wastelands and wild vegetation on crop field boundaries which otherwise provide suitable breeding groundslhabitat and alternative food to rodents. Bandicoot rats make extensive burrows usually in bunds and the earthen embankments of water channels. They prefer tall and thick bunds for burrowing and a reduction in bund thickness and height discouragesthem. Certain cultural practices affect the incidence of rats and their damage to crops. Deep tillage and ploughing of vacant land around fields destroy rat burrows and drives them away. Being a lang duration crop, cane fields are frequently threatened by waves of rodent immigration related to agricultural operations in the adjoining fields like paddy. Rotation of paddy with crops like sunflower may break the food cycle and reduce immigration to sugarcane. Since rats cause more damage to a lodged crop, adoption of techniques such as wrapping and propping of the standing crop, irrigation according to wind intensity and the use of varieties which may not lodge indirectly help to prevent damage by rats. In sugarcane more damage occurs to varieties with a thin barrel, soft rind, low fibre and lodginghabit than in the varieties with a thick barrel, hard rind, more fibre and non-lodging habit. (~echanlcalmethods
Mechanical techniques such as hunting, killing and trapping often involve high labour costs and are less practicable over large areas. However, these can be integratedwith chemical control techniquesto achieve better control success. Bandicoot rats can be driven out of burrows by ploughing the fields during the period between crops, flooding of burrows with irrigation water and digging or smoking the burrows by burningcow dung cake or rice straw. Acommon old practice is trapping rats in fields and premises using two basic types of traps, the snap or kill trap and the live trap. The common kill traps used are Tanjore Bow trap, wooden snap trap, urangor arrow trap and breakback spring loaded snap traps with wooden or jawed iron base. Live trapping is done using primitive type pit fall or pot trap, foldable iron sheet boxes with a spring loaded shutter and wonder traps of different sizes and shapes.
( Chemical methods The use of rodenticides is the most common aplproach to control rodents in agricultural, rural and urban environments. Their effectiveness depends upon the selection of an appropriate compound, its formulation, and the method and timing of application.The commonly used I recommended rodenticides in India are the acute rodenticides, viz. zinc phosphide and aluminium phosphide, and the anticoagulants warfarin, racumin and bromadiolone. It will be useful to close or smoke the burrows a day before to locate the active burrows in the field. Zinc phoshide is an acute rodenticide and hence single dose is sufficient to bring about rodent mortality. For controlling rats, cereal bait (mixture of broken wheat grains, sugar powder
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and groundnut oil (96 : 2 : 2) recommended. For the baits to be bait aversion bv rats. This is done containing no iinc phosphide to acclimatize th; field populations of rats with:. the food source. On the 3' day, 10 grams of the zinc phosphide bait is placed in the live burrows for controlling the pest. Besides pre-baiting, bait aversioncan also be reduced by changing the cereal base and its texture, and leaving a sufficient time gap between two consecutive treatments. Fumigation of' burrows with aluminium phosphide is generally effective in damp soils but its importance is limited by toxicity hazards, cost of application and low efficacy aga~nstspecies like B. bengalensis.
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The chronic rodenticide warfarin is another chemical used in India for rodent control. Unlike zinc phosphide, warfarin is an anticoagulant poison and less toxic to non-target organisms. However, warfarin 0.025% baits have to be consumed for 5-7 days to bring about desired results. Since warfarin is a multiple dose rodenticide it increases the cost of operation of rodent control. In order to overcome the problem of prolonged prebaiting, hazardous nature and possibility of development of resistance to single dose acute rodenticide like zinc phosphide and multiple dose chronic rodenticide like warfarin, second generation anticoagulants like br~madioloneare now widely used for rat control. Bromadiolone 0.005% bait combines the better qualities of acute and chronic rodenticides as it is a single dose anticoagulant and less toxic to non-target species. Bromadiolone baits will be more suitable than aluminium phosphideforthe control of immigrant populations. Packageof recommendations
An integrated approach incorporating the following methods will ensure longt e n prevention and management of both resident and immigrant populations of rats. It is imperative to adopt control measures involving all farmers, on a campaign basis over large areas, for successful rodent management in sugarcane and other crops. Removal ofwild vegetation or weeds Reduction in bund thicknessand height Deep tillage and ploughing of vacant land around fields Rotation of paddy with crops like sunflower to reduce immigration to cane Wrapping and propping of the standing crop Trapping in fields using suitable devices Fumigationof burrows with aluminium phosphide tablets Use of baits (zinc phosphide/bromadiolone) ExtensionPublication No. 148 (2007)
Script by
: Dr. B. Singaravelu, Dr. J. Srikanth,
Dr. N. Geetha, Dr. R. Jayanthi Prepared by
: Dr. T. Rajula Shanthy, Dr. R. Thiagarajan, Dr.D. Puthira Prathap
Publishedby
Dr. N. Vijayan Nair Director, Sugarcane Breeding Institute Coimbatore 641 007
Printed by
Printrite, Coimbatore
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