Plant based, eco-friendly wood preservatives for termite control Track/Theme: Sustainable consumption, consumer responses and new markets for ecoproducts OR Climate Change and energy VERMA Monica*, SHARMA Satyawati and PRASAD Rajendra Centre for Rural Development and Technology Indian Institute of Technology Delhi Hauz Khas, New Delhi – 1100016 E-mail: [email protected] * Main author and presenter Abstract Termites are the most troublesome pest of agricultural crops and wooden structures, causing billions of dollar damage annually through out the world. Most popular and widely used prevention measure to reduce the infestation of termites is the use of synthetic termiticides. These are very harmful chemicals. Several termiticides are registered for termite control across the world under various brand names like spinosad, disodium octaborate tetrahydrate (DOT), calcium arsenate and chlorpyriphos. Although, chemical control is an effective measure of protection by termites but their excessive use is harmful for our environment and the results are not sustainable. Many researchers are trying to develop new methods of termite control. Plant derived natural products, entomopathogenic fungi, nematodes and bacteria are some of the alternative methods of termite control. Some plant biomass contains insecticidal activity which can be exploited for termite control. Present paper deals with field level results of work done at micromodel CRDT, IIT Delhi on the efficacy of certain selected plant biomass in controlling termites. 14 plants having insecticidal activity were procured from IIT Delhi campus. They were screened for their termiticidal activity. A chemical, chlorpyriphos was also used for comparisons. Out of 14, 5 botanicals were found to be effective against termites. Although some botanicals were not as effective as chemical but they are nontoxic and safe for the environment, biodegradable and renewable source. The plant extract could be exploited to develop new wood preservatives to protect wooden structures, agricultural crops, plants and trees, as these are less harmful to the environment and humans. Further, studies are required to use them as commercial termiticide. Keywords: Termites, botanicals, termiticides, chlorpyriphos 1. INTRODUCTION Termites are the most troublesome pest of plants, trees and wooden structures. They severely damage agricultural crops and urban infrastructure. There are about 2,500 species of termites in the world and only 10% have pest status. Out of 300 species in India, about 35 have been reported as damaging agricultural crops and timbers in buildings. They cause over 3 billion dollars in damage to wooden structures annually throughout the United States [8]. In India, they cause the yield loss of 15- 25% of maize and about 1,478 million Rupees [7]. Termites can attack plants at any stage of development from the seed to the mature plant. Crop losses and termite genera responsible in different continent and different termite genera in subcontinent is described in Table 1 and 2 respectively. They are social insects that live together as a colony in a nest. Colony members belong to one of three interdependent groups with specialised form and function known as castes. The three basic castes present in the colony are workers, soldiers and reproductive forms. Workers and soldiers are wingless, sterile and blind. Workers construct the distinctive shelter tubes and collect food to feed the young and other members of the colony. The primary function of the soldiers is to defend the colony, usually against ants, which are their main enemies. The reproductive caste is usually referred to as the king and queen. They are responsible for the production of fertilised eggs for the colony and of specialized chemicals (hormones) important for managing the inhabitants of the colony. Mature colonies produce winged reproductive forms or alates at certain times of the year. After the dispersal flight, the alates attempt to find mates and found new colonies [5]. Termites are most successful of all the social insects because colony members are long lived and because they utilize cellulose as food source. They depend entirely over wood, either living or dead, or the woody tissue of plants, intact or partially decayed and also in the form of humus and dried animal dung. Termites which belong to the following families and genera: Hodotermitidae (Anacanthotermes and Hodotermes), Kalotermitidae (Neotermes), Rhinotermitidae (Copotermes, Heterotermes, and Psammotermes), and Termitidae (Amitermes, Ancistrotermes, Cornitermes, Macrotermes, Microcerotermes, Microtermes, Odontotermes, Procornitermes, and Syntermes) cause great losses in agriculture [17]. Table 1. Crop losses and termite genera of different continents Country Africa Crop Groundnut Maize Sugarcane Losses (%) Termite species Between 10 Microtermes and Odontotermes and 30 30- 60 Microtermes, Ancistrotermes Macrotermes spp. Odontotermes, Allodontermes, and 5-10 (Central Pseudacanthotermes Africa) Amitermes, Pseudacanthotermes, Macrotermes, 18 (Sudan) Odontotermes, Microtermes and Ancistrotermes Southeast Asia Sugarcane 12 (Pakistan) Australia Cashew, mango 30 and avocado trees Microtermes, Coptotermes, Odontotermes, Macrotermes, Trinevitermes and Heterotermes. Mastotermes, Heterotermes, Coptotermes, Amitermes and Microcerotermes Source : www.chem.unep.ch/pops/termites Table 2 : Important termite genera in subcontinents Country Southern Africa Important termite genera and species Anacanthotermes (Family Hodotermitidae), Psammotermes and Reticulitermes (Family Rhinotermitidae), Amitermes, and Microcerotermes (Family Termitidae), and several species of Kalotermitidae Eastern Macrotermitidae: Macrotermes (Family Termitidae), Hodotermes (Family Africa Hodotermitidae), and Schedorhinotermes (Family Rhinotermitidae). Western Ancistrotermes, Macrotermes, Odontotermes, Microtermes, and Africa Cubitermes(Termitidae). N. America Dampwood termites: (genus Zootermopsis, Family Termopsidae) Drywood termites: (Incisitermes, Neotermes Subterranean termites (Reticulitermes, Heterotermes, Amitermes, and introduced species of Coptotermes S. America Cryptotermes and Neotermes (Family Kalotermitidae), Coptotermes and Heterotermes (Family Rhinotermitidae), and Nasutitermes China Coptotermes, Reticulitermes (Family Rhinotermitidae), Macrotermes and Odontotermes members of the Cryptotermes (Kalotermitidae) and Hodotermitidae Australia Subterranean, drywood, harvester, and mound builders Mastotermes, porotemes, stolotemes (primitive genera) Europe Reticulitermes Source: www.chem.unep.ch/pops/termites Control measures A number of control measures are used to prevent termite attack on buildings as well as on crops. These are physical, chemical and biological. Physical Physical method of control includes physical barriers and treatment. Barriers are of two types: non toxic and toxic. Non toxic physical barriers are substances (e.g., sand or gravel aggregates, metal mesh or sheeting) that exclude termites through the impenetrable material act as a physical/mechanical barrier to prevent termite penetration and damage to building and toxic chemical barrier includes the use of chemical termiticides in soil around the building and creation of a zone of poisoned soil under and around the structure to prevent termites entering from the ground [3]. Treatments consist of heat, freezing, electricity and microwaves. Chemical It is the most important and most widely used prevention measure to reduce the infestation of termites. Several termiticides are registered for termite control across the world under various brand names. They contain the following active ingredients: bifenthrin, chlorfenapyr, cypermethrin, fipronil, imidacloprid and permethrin. Various chemicals spinosad, disodium octaborate tetrahydrate (DOT), calcium arsenate and chlorpyriphos are also used. The chemical toxicity, formulation and application method, as well as dry wood termite behavior and gallery system, architecture influenced the performance of local chemical treatment [14]. Chemical Treatments comprises groomable coating, soil termiticide injection, baits and chemical fumigation [6]. Chromated copper arsenate (CCA) treated southern yellow pine and radiata pine was found to be toxic against formosan subterranean termites, Coptotermes formosanus [4]. Soil termiticide injection, used for subterranean termites. It includes drilling of the foundation wall/slab, injection of termiticide from below slab and in the soil in contact with foundation. Plugging drill holes on interior with cement, or caulking [6]. Chemical Fumigation usually used for drywood termite infestation. This strategy is employed to deal with drywood termites, aerial colonies of subterranean termites and cases where arboreal species nest inside structures. It includes the use of toxic gas inside the structure. Removal of all chemical absorbent materials from the building to be fumigated. Tenting of whole building and evacuation of surrounding properties followed by pumping in of fumigant and allowing time to penetrate the wood finally venting of gas and removal of tent [6]. These gases must be used with extreme care, because they are extremely toxic to humans, as well as other animals, and plants. Improper or careless use can result in death or injury. Fumigants treat all termite infestations or colonies simultaneously, and have high levels of efficacy, if correctly applied. Active ingredient in various fumigants are Carbon Dioxide (Asphyxiant), Methyl bromide, Phosphine, Sulfuryl fluoride (Metabolic poison). Methyl bromide is a commonly used fumigant [17]. Baiting is an environmentally sound method of termite control. It uses very small amount of insect toxicants. Baits can be toxic or nontoxic. Bait technology uses wood or a cellulose matrix favored by termites that is impregnated with a slow-acting toxic chemical. The workers were exposed to lethal dose of desirable food bait. Bait station is placed into soil at intervals around building, baits inside contains slow-acting chemical. Termite workers feed upon the bait and transfer it by grooming or trophallaxis (licking) to other colony members, thereby reducing or eliminating the entire colony. Bait consumption by termite depends on bait design [2]. Termites are not site-specific, but rather, they forage among various food sites, which results in the bait being encountered by many colony members. The toxicant necessarily is slow acting because termites tend to avoid sites where sick and dead termites accumulate. Successful termite baiting necessitates proper monitoring and maintenance of the stations. Baits are often used in sensitive environments. A number of baits have been marketed to control termites. The bait product contains the following ingredients: diflubenzuron, hexaflumuron, sulfluramid and noviflumuron. Among them hexaflumuron is the most popular bait toxicant (Table 4). Table 4. Different bait toxicant, their mode of action and application Active Ingredient Mode of Action Application/ Considerations Diflubenzuron Chlorflurazuron Hexaflumuron Triflumuron Disodium octoborate Chitin synthesis inhibitor Chitin synthesis inhibitor Chitin synthesis inhibitor Chitin synthesis inhibitor Metabolic toxin In food matrix In food matrix In food matrix Dust In food matrix/dust tetrahydrate Arsenic trioxide Hydramethylnon Sulfluramid Biocontrol Agents Fungus: spores, mycelium. Nematodes: stages Metabolic toxin Metabolic inhibitor Metabolic Inhibitor Dust In food matrix In food matrix Grows through cuticle andUse as bait and soil utilizes entire termite body treatment is experimental. infective Invade; carry bacterium which Bait system is experimental produces lethal toxins Source: www.chem.unep.ch/pops/termites Biological control Alternative means for pest control should be searched to minimize the use of synthetic chemicals. The use of botanicals and biocontrol agents are a promising alternative to chemical control. Botanical pesticides possess an array of properties including insecticidal activity, repellency to pests, antifeedency, insect growth regulation, toxicity to agricultural pests [9, 10, 11, 12, 13]. Plant derived natural products, entomopathogenic fungi, nematodes and bacteria are some of the alternative methods of termite control. Nematodes caused high mortality of Reticulitermes flavipes (Kollar) termites in laboratory tests [16]. The entomopathogenic fungi play significant role in integrated pest management [1]. Beauveria bassiana (Balsamo) Vuillemin has been shown to be highly pathogenic to many insect species in both temperate and tropical regions [15]. A fungus Metarhyzium aniospliae (Bio Blast) is another biological termiticide that require special application and handling technique. 2. METHODOLOGY 2.1 Plant materials Leafy biomass of 14 plants (Asafoetida, Azadirachta indica, Calotropis gigantea, Cannabis sativus, Curcuma amada, Datura alba, Eucalyptus globulus, Jatropha curcus, Lantana camara, Musa paradisiaca, Pongamia pinnata, Parthenium hysterophorus, Ricinus communis and Tagetus erecta) was collected from Indian Institute of Technology Delhi, campus. Hot water extracts of 10% concentration were prepared by boiling 100gm of the selected plant biomass in 1 liter of distilled water for 1 hour then left it for further extraction. Thereafter, it was decanted and filtered with Whatman filter paper. A pesticide chlorpyriphos (O,q O–diethyl O -3, 5, 6- trichlor-, O - 2pyridylphosphorothioate) was also used for comparisons. 2.2 Termite test Wooden blocks of kail wood (Pinus excelsa) of size (26 x 4 x 1 cm3) were dried in the oven at 60 o C overnight and weighed. Before treatment, all test blocks were conditioned at 27o C and 70% relative humidity (RH) for two weeks. They were dip-treated with plant extracts overnight in plastic trays. The extract and chemical treated blocks were air-dried and inserted into termite infested area in IIT campus. The blocks were observed daily. 2.3 Mass loss analysis After four weeks period, the blocks were removed, cleaned, dried overnight and weighed to determine weight loss. Loss in weight of blocks was recorded as percent mass loss. 3. RESULTS AND DISCUSSION Termite test Wood consumption (as per mean % weight loss) of extract treated and untreated blocks by O. obesus are given in Table 1. Aqueous extract of Cannabis sativus leaves caused significant protection with 4.94% of P. excelsa wood loss against Odontotermes obesus. Similarly, extracts of Datura alba fruits, leaves of Curcuma amada, Asafoetida and Ricinus communis provided effective protection with 10.50, 11.19, 11.28 and 16.33 % wood weight loss respectively. Therefore, these treatments are effective against biodeterioration of wood by O. obesus. The chlorpyriphos treated wooden blocked was unattacked by termites through out the test period. The control blocks were completely consumed by termites as there was no barrier of any protective coating around them. This suggests that though chemical are an effective control against termites but they are harmful too. Therefore, search of alternatives control measures is essential. These botanicals can be used in combination with chemical pesticide to lower their harmful effect. Table 1. Percentage weight loss of wood blocks treated with 10% concentration of various Leaf extracts. Treatment Mean weight loss (%) (Mean ± SD) Asafoetida Azadirachta indica Calotropis gigantea Cannabis sativus Curcuma amada Datura alba Eucalyptus globulus Jatropha curcus Lantana camara Musa paradisiaca Pongamia pinnata Parthenium hysterophorus Ricinus communis 11.28± 0.08 15.77± 2.66 48.43 ± 4.09 4.94 ± 1.61 11.19 ± 0.08 10.50 ± 6.27 49.07 ± 32.02 51.17 ± 5.95 45.13 ± 11.79 47.37 ± 4.32 48.40 ± 8.75 40.80 ± 6.70 16.33 ± 3.97 Tagetus erecta Chlorpyriphos Control 23.60 ± 3.54 0.00 100.00 4. CONCLUSION In the present study the extracts of Cannabis sativus, Datura alba, Curcuma amada, Ricinus communis and Asafoetida were found to be effective against termites. Although some botanicals were not as effective as chemical but they are nontoxic and safe for the environment, biodegradable and renewable source. 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