Rodent pest/vector species
In world scenario, three rodent species are commensal co-existing with humans in urban situations. They include Sewer rat, Rattus norvegicus, House rat, Rattus rattus and House mouse, Mus musculus. The latter two have wider distribution all through the Globe and contribute for structural damages including electronic installations, disease transmission to humans and farm animals, and food adulteration through faeces and hair.
The nibbling habits and smaller body size make House mice as potential threat to cables and storage commodities. In Indian scenario, the spread of Lesser bandicoot, Bandicota bengalensis and Larger bandicoot, Bandicota indica in urban areas accentuated the rodent related problems. The bandicoots are replacing the house rats in most of the urban situations in the country, due to expansion of colonies in the agricultural areas and their aggressive behaviour.
Potentiality for Structural Pest Management Industry
The sectors which provide more revenue for rodent pest management include
i) Food Industry contributing to 14% of manufacturing GDP i.e. `280,000 crores,
ii) Hospitality Industry with an estimated growth from `74 billion to `119 billion from 2010-13, and
iii) IT Industry contributing to 7.5% to GDP and market of US$ 50 billion and expected to double its growth in 2011-12
Rodent Pest Management Options
With regard to rodent pest management, basic difference exists in agricultural and industrial or domestic situations. In most of the industrial situations, rodents are to be excluded totally from certain areas to avoid damage to sensitive installations or expensive equipment. Even a single mouse could cause loss of several lakhs of rupees and can create technical snags in aircrafts. In agricultural situations, their number should be kept below the threshold level. Integration of different methods gives the desired management success. A number of options exist for their management with each option having its own limitation.
Trapping is an age old method adopted for rodent control in residential premises. Live traps – wonder and box type are used in domestic/industrial situations. Kill or Snap traps are also used, which will kill the rodents instantly on touching the trigger. These traps are effective for tackling localized rodent infestations. Trap shyness of rodents and pheromonal communication among rodents often impact the efficacy of trapping method. Non poisonous sticky traps are effective to remove traces of mouse/rat infestations in expensive/sensitive establishments. Hence, they gained popularity as a tool in excluding localized infestations effectively. However, their usage is restricted recently by Ministry of Environment and Forests on cruelty issues arising out of struggle by the rodents on the glue boards.
Although Predators like cats are often reared in domestic situations, they are found to remove effectively surplus rat/mouse populations that are immigrating in to the premises from adjoining areas. The local established rats/mice are un effected. Further, the predators posed a threat of zoonotic diseases and this tool was to be abandoned in Cairo by the Government, after its legal implementation over couple of years in early 1980s.
Ultrasound devices producing sound vibrations above 20kHz are being used to prevent the immigration of rodents in closed door storage situations. The commensal rodents acclimatize to the ultra sound on continuous exposure. Hence their usage has its own limitations.
Attractants and repellents were tried for rodent management, but so far no effective repellent could be developed in urban situations. Although evidence suggests usage of rodent pheromones as promising to increase/decrease their populations, no attempt is seriously made to identify, isolate and synthesize those pheromones.
Effective chemosterilants are not available. Effort is being made to introduce a male sterilant in India. But due to biotechnology implications, the registration process is at slow pace.
Rodenticides, boon or bane
Rodenticides are most commonly used tool against commensal rodents. They are potential in tropical situations with long future, but much remains to be done to optimize their use. In India, only zinc phosphide and bromadiolone are available in market. Although aluminium phosphide pellets are recommended for rodent burrow fumigation, it needs permission from CIB&RC for use within India.
Due to toxicity and environmental safety reasons, the use of zinc phosphide is not advocated in domestic areas. However, in open fields it is recommended at 2.5% TG in cereal baits. Neophobia and bait shyness are limitations to use this rodenticide. Ready-to-use formulations are not available with this acute rodenticide and such formulations can reduce the risk of exposure of non-target species to higher concentrations.
Aluminium phosphide is one of the most abused fumigant, most often making 3g tablet in to two pieces and applying in rodent burrows with utter disregard to the safety of the operator. Such an action makes immediate release of lethal phosphine gas affecting the operator. In view of this, a 0.6g pellet of this fumigant @ two per active burrow is recommended for rodent control. Further, this fumigant is restricted for use under the technical supervision of competent technical personnel. Efforts are under slow pace to develop 1.5g formulation for rodent burrow fumigation.
Anticoagulants delay anticoagulant action and won’t induce bait shyness since no immediate effect is felt by the rodents. among the rodent species and hence could be used for effective rodent control. Hence, application of anticoagulants would tackle both neophobia and bait shyness problems. Coumatetralyl TP, a first generation anticoagulant is used in cereal mixed baits at 0.0375% mostly in storage/domestic situations. Lower toxicity level, chronic action and availability of vitamin K? antidote made it as an effective anticoagulant in residential premises.
However, it is not available in market. Bromadiolone, a second generation anticoagulant is recommended under IPM packages for rodent control in field situations as well as in storage/domestic situations. It is recommended in cereal baits at 0.005% a.i. and very effective when used with bait stations. It is also recommended in ready-to-use formulation to tackle rodent infestations in plantation crops and in storage. Efforts are in progress to bring out new molecules of anticoagulants. Difethiolone, a hydroxy-coumarin derivative exhibited promising field results with lesser LD? and short kill.
However, reports on predator mortality and secondary/accidental toxicity with these new generation anticoagulants evoked second thinking among scientific fraternity on introducing newer second-generation anticoagulants.
Application Technology
Irrespective of the method used to tackle the commendal rodent populations, the effictiveness depends on the method of application. Placement of traps, bait material plays significant role since commensal rodents are thiegmotactic in nature. Further, baiting through bait stations are effective since rodents readily enter inside and consume the baits. Fine-tuning of application technology is very essential for effective rodent management with least environmental contamination/hazards.
Research and Development
Although research is in progress to evolve new methodologies for effective rodent management by ICAR All India Network Project on Rodent Control, the work is mostly restricted to field rodents. There is a dire need for research covering the urban areas and to develop technologies suited for effective rodent management with least environmental effects. The Structural Pest Management Industry may consider extending funding for some such identified projects.
Status of structural pest management industry
The contribution of structural pest management industry is very significant in the present scenario. It is essential to have competent technical personnel to plan and implement the rodent management at clients’ place. There is also a need to have trained contingent of operators, on whose capability the result will depend. Scientific expertise on rodent control is very much limited in India. The National Institute of Plant health management took initiative of capacity building for professionals of Structural Pest Management industry to provide qualified planners in Urban Integrated Pest Management.
Similarly efforts are under progress to accord fine tune the curriculum and extend accreditation of capacity building programs conducted by Structural Pest Management Associations given to the Pest Control Operators in india. Secondly, the review on the available rodent management technology for commensal rodents suggests strongly a need for the industry to have R&D to the extent possible to tackle the ever increasing problem. Such an effort will make the industry to face challenging situations in rodent pest management
References
Hadler, M.R. and Buckle, A.P. 1992. Forty years of anticoagulant rodenticides – past, present and future trends. Proc. 15th Vertebrate Pest Conference, Davis, pp. 149-155.
Mohan Rao, A.M.K. and Balasubramanyam, M 1992. The mice Mus. Spp. In: Rodents in Indian Agriculture. (Ed. Prakash, I. And Ghosh, PK) Scientific Publishers, Jodhpur, 147-164.
Mohan Rao, A.M.K. 1992. Changing scenario of rodents in India. In: National Seminar on changing scenario in pest Management in India. (Ed. Rao, M V B and Sharma, H C) Hyderabad, 203-208.
Mohan Rao, A.M.K., 1992. Integrated rodent pest management. In: Rodents in Indian Agriculture (Prakash, I and Ghosh, P.K. Ed.), Scientific Publishers, Jodhpur, 651-658.
Mohan Rao, A.M.K., 1992. Rodent problems in India and strategies for their management. In: Rats, Mice and People: Rodent Biology and Management (Eds. Singleton, GR., Krebs, CJ and Spratt, DM), ACIAR, Canberra: 229-232.
Rana, B.D. and Tripathi, R.S. 1999. Recent advances in coordinated Research on Rodent Control. Central Arid Zone Research Institute, Jodhpur, 48 pp.
Dr AMK Mohan Rao National Institute of Plant Health Management Hyderabad This paper was presented at the recently concluded FAOPMA 2011 in Goa