Introduction

Termites are usually called “white ants” because the majority of them are white and small and live in large colonies much like the ants.  The great economical importance of the termites can be judged from the estimates of losses caused by them to crops and forests made from time to time by different workers (Bignell and Eggleton, 2000).  Termites prefer to feed on soft spring growth wood rather than hard woods and woods rich in natural chemical protectants. Some woods (e.g. red woods, cypress, and juniper) are less preferred by termites, but no wood is completely immune to attack. In general, termites prefer cellulose that is easy to obtain. E.g., in laboratory studies they prefer in this order:  loose cellulose fibers > paper > cardboard > softwood blocks > hard wood blocks.

Methodology

The field experiment was set up within the limits of subdivision Naraingarh of district Ambala from Nov 2006 to Oct 2007. Ambala lies on north eastern edge of Haryana between 27- 39”-45’ North latitude and 74- 33” 53’ to 76-36”- 52’ East longitude. It is bounded by district Yamuna nagar to south east. To its south lies Kurukshetra district while in its west are situated Patiala and Ropar district of Punjab and the Union Territory of Chandigarh. The Shivalik range of Solan and Sirmaur district of H.P. bounds the Ambala district in North and North-East. The height from the sea level is 900 feet.

For the present study different areas having termite infestation were observed and four sites were selected to set up different experiments during Nov. 2006 to Oct. 2007 in the Naraingarh subdivision of Ambala District. Preference of wood was observed in the above mentioned experiment by calculating species wise mean per cent loss of all the 3 experiments. All the species were compared on the basis of mean per cent loss and were categorized in different categories depending upon preference.

Experiment was conducted to observe the preference of wood. Four different plant species viz. Safeda (Eucalyptus sp.), Dhrek (Melia sp.), Shisham (Dalbergia sisoo) and Kikar (Acacia indica) were used. Small logs having both sap wood and heart wood were weighed and placed at the termite infested sites for six months. Final weight was calculated and per cent weight loss was compared to the earlier experiment of same duration i.e. six months.

Results and Discussions

Minimum three samples of all the eight wood species were studied by grave yard method. Only heart wood was placed without any seasoning or treatment. In another experiment four wood species were studied by same method in which sap and heart wood both were present.

On the basis of per cent loss of wood by termites during the test period, the resistance of tested wood or preference of wood by termites was graded into following various classes.

Eight species were investigated against the attack of termites with regard to their natural termite resistance quality and wood preferred by termites. Out of these, three species proved to be very resistant to termite viz. Shisham, Sal and Safeda which shows that these are least preferred by termites. These were placed in Category I, Table-11, where the mean per cent loss was below 10.0 i.e. very resistant. Weight loss vary for Eucalyptus 5.26 to 12.24 (mean per cent wt. loss 8.21) for Dalbergia 5.61 to 12.00 (mean per cent wt. loss 8.27) and for Shorea 5.93 to 12.50 (mean per cent wt. loss 8.66), Table 4, 6 & 8. It was revealed that these were not eaten by termites and if eaten, to very less extent. It may be due to the presence of other preferred wood species present near by. Other reason for natural resistance of these species may be due to presence of volalite substance in heart wood.

Acacia and Prunus is placed in category II, Table-11 and damaged caused to these woods is very less. Per cent weight loss vary from 10.42 to 21.10 (Mean per cent wt. loss 14.64) for Acacia. Per cent weight loss vary from 6.06 to 14.71 (Mean per cent wt. loss 9.76) for Prunus. Hence these woods are not preferred by termites, Table-4 & 5.

Damage caused to Melia sp. wood is also considerable i.e. between 16 – 20 (Mean per cent wt. loss) hence placed in category III, Table-11, In Melia sp. per cent loss vary from 12.67 to 22.58 and the mean per cent wt. loss was 17.36, so it is poorly resistant to termites, Table-6.

Table 1: Per cent Weight Loss of Wood Safeda (Eucalyptus sp.) due to attack by Termites.

Table 2: Per cent Weight Loss of Wood Shisham (Dalbergia sisoo) due to attack by Termites.

Table 3: Per cent Weight Loss of Wood Sal (Shorea robusta) due to attack by Termites. 

Table 4: Per cent Weight Loss of Wood Kikar (Acacia indica) due to attack by Termites.

Table 5: Per cent Weight Loss of Wood Jamoya (Prunus padus) due to attack  by Termites.

Table 6: Per cent Weight Loss of Wood Dherk (Melia azadarach) due to attack by Termites

Table 7: Per cent Weight Loss of Wood Mango (Mangifera indica) due to attack by Termites.

Table 8: Per cent Weight Loss of Wood Neem (Azadirachta indica) due to attack by Termites.

Table 9: Per cent Weight Loss of Different Woods (including Sap and Heart Wood) due to Attack by Termites (After 6 months).

Table 10: Per cent Weight Loss of Different Woods due to Attack by Termites (After 6 months).

 Table 11: Comparative Statement of Termite Resistance Class of different Wood Species

The species (wood) which were most preferred by termites are Mangifera and Azadirachta. These were placed in Category IV, Table-11, where the mean per cent loss was above 20 i.e. perishable. It was found that these woods were eaten at very fast rate by termites and weight loss vary for Mangifera 26.19 to 38.30 (Mean per cent wt. loss 31.91) and for Azadirachta 22.73 to 32.74 (Mean per cent wt. loss 27.33) which is too high (Table-7 & 8).

It was further observed that outer sap wood is more preferred by termites as compared to heart wood. It is very clear from the observation of wood samples as presented in photographs of Dalbergia sisoo and Eucalyptus spp. This is also evident from the table 12, where the per cent weight loss in Eucalyptus is 19.11, Melia 31.25, Dalbergia 35.44 and Acacia 41.65. When this loss is compared with the loss caused to only heart wood in Table-10, it is very much clear that the preference of termite is sap wood instead of Heart wood. This might be due to the presence of volatile substances in the heart wood.

Similar experiment was conducted by Sen-Sarma in 1974 on 29 different wood species. He categorized these woods in five categories depending upon their termite infestation. We in our experiment also categorized the 8 species depending upon their termite resistance but only two species (Dalbergia and Melia) are common in our and Sen-Sarma experiment. In his experiment he compared outer heart wood region and inner heart wood region although, we compared the sap wood and heart wood in four wood species in our experiment.

In the field, preference for a particular cellulose resource is likely determined by its availability, size, textures and nutritional demand of the termite colony. There is some evidence that termites prefer wood that has been attacked by certain wood destroying fungi. Other fungi may deter termite feeding.

According to Juan A. Morales-Ramos and M. Guadalupe Rojas 2000; the feeding preferences of the Formosan subterranean termite, Coptotermes  formosanus Shiraki were tested in three separate experiments on 28 different wood species. Preference was determined by consumption rates. Birch (Betula alleghaniensis Britton) red gum (Liquidombar styraciflua L.) Parana pine (Araucaria angustifolia (Bert), sugar maple (Acer saccharum. Marsh) Pecan (Carya illinoensis Wangenh) and northern red oak (Quercus rubra L.) were most preferred species by C. formosanus in order of consumption rate. All of these species ere significantly more preferred than southern yellow pine (Pinus taeda L.) widely used for monitoring. Sinker cypress[=old growth bald cypress, Taxoduim distichum (L.)] western red cedar (Thuja plicata Donn), Alaskan yellow cedar (Chamaecyparis mootkatensis D.Don ), Eastern red cedar (Juniperus virginiana L.), sassafras [Sassafras albidum (Nutt)]  Spanish cedar (cedrella odorata L.), Honduras mahogany (Swietenia macrophyla King), Indian rosewood (Dalbergia latifolia Roxb.), Honduras rosewood (D. stevensonii Standl.) and morado (Machaerium sp.) Induced significant feeding deterrence and mortality to C. formosanus .

Laboratory tests to determine natural resistance of several Indian timbers have been carried out by Sen-Sarma (1963a.b,c, 1972; Sen-Sarma and Chatterjee 1965b, 1968) and Sen-Sarma et al. (1975). Natural termite resistance of eighty four Indian timber species has been tested so far by Sen-Sarma et al. (1975). Sen-Sarma (1970) has given an exhaustive account of various methods of laboratory evaluation of termite resistance of wood and wood products. Gupta and Sen-Sarma (1981) have investigated the anti-termite properties of some anthraquinone derivatives of teak. Heartwood of teak shows wide variation in termite resistance. Sen-Sarma and Thakur (1979b) are of the opinion that the termite resistance in teak is perhaps genetically controlled.

Various reports dealing with the status of termites on crops and trees in India have been reported and published by Sen-Sarma and Thakur (1983,1985,1986), Khan and Singh (1985), Nair and Varma (1985), Verma (1986), Sen-Sarma (1987), Das (1988), Verma (1989,1993), Cowie et al. (1989), Varma (1990), Bhanot et al. (1991) and Girdhar (1995).

Acknowledgments

Authors are thankful to the farmers of Naraiangarh region and officials of Agriculture Department, Haryana for their cooperation and guidance. Thanks to Coordinator, IGNOU, M.N. College, Shahbad (M) for providing lab facilities

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