Comparative Evaluation of Bait Materials and Bait Stations for Subterranean Termites

Author: S. Sathyapritha*, K. Premalatha, P.S. Shanmugam, S. Harish, S.V. Krishnamoorthy

Journal Name:

Download PDF

Abstract

The baiting tactics for the management of subterranean termites had variable outcomes in the past depending on several characteristics of the bait such as moisture retention, termite attraction, durability and so on. The subterranean termites avoid tunnelling within dry bait, potentially reducing bait infestation and its consumption. Hence it is necessary to standardise the bait material which retains optimum moisture content without rendering its potential to attract the termites. The various combinations of bait materials and bait stations were evaluated based on moisture content and termite attraction, under laboratory condition. The coconut leaf bait in the plastic container retained higher moisture of 50.61%, fifteen days after placement (DAP). In field study, the attractiveness of baits were studied based on the population of termites at different intervals 3, 9, 15, 21 DAP and its feeding percent. The mean population of termites and feeding percent were higher upto 15 DAP in the order, coconut leaf bait > combination bait > paddy straw bait > cut bait. Hence coconut leaf bait in the plastic container would be further used for the field studies.

Keywords

Termite, Bait material, Bait station, Moisture content, Foraging activity

Conclusion

From the comparative evaluation, plastic bait station with the coconut leaf bait was standardised for further field studies. The coconut leaf bait in the plastic container retained comparatively higher moisture content at 15 DAP and higher attractiveness for termites in field conditions. The high cellulose content (45.58%) and high moisture retention capacity distinguishes plastic container along with coconut leaf bait. The bait can be replaced after 15 days for long term control.

References

INTRODUCTION Termites are decomposers of dead woods and dead plant materials which contribute to the soil nutrient recycling. But their active search for the cellulose results in substantial harm to crops, perennial trees, buildings, wooden structures etc. They are found in a wide range of ecosystems, including tropical and subtropical climates, low and high altitude forests, agricultural farms, pastures, wooden structures & buildings, libraries and also in urbanised areas justifying its omnipresent nature (Rasib and Wright 2018). Approximately 3107 termite species are known world-wide, in which 80 species are considered to be serious pests (Kuswanto et al., 2015). The global economic impact of termites is estimated to be USD 40 billion per year, with subterranean termites accounting for over 80% of the entire economic impact (Oi, 2022) which entails to control these cryptic species in an effective and ecologically sound methods. As far as India is considered out of 337 species recorded, 92 species are wood despoilers (Shanbhag and Sundararaj 2013). Application of any management measures are restricted to a very small portion of the tunnel system that are obvious. The hidden network of the open tunnel may contain a colony with millions of termites inhabiting in it. Any ideal method of control should disseminate the active ingredient from the exposed workers to their hidden nestmates (Rust and Su 2012). For decades, soil termiticides were the standard treatment method, but concerns about human and environmental health, less transfer efficiency between the nestmates prompted the development of alternatives. Baits are an excellent method to control, since they take advantage of their foraging habits and social interactions viz. trophallaxis and grooming for the horizontal transfer of residual pesticide deposits between nestmates. The horizontal spread of bait throughout the colony is facilitated due to the delayed action and non repellant qualities of the active component used in bait rather than the rapid acting chemical used as termiticides. In addition to the active ingredient, the efficacy of the bait depends on its moisture content, palatability, diet source and its attractiveness (Rasib and Wright, 2018). Hence the following studies were conducted to evaluate and standardise the bait sources and bait stations based on the moisture content and its duration of attractiveness for termite foraging. MATERIALS AND METHODS The experiments were conducted at Department of Agricultural Entomology, TNAU, Coimbatore. A. Studies on laboratory evaluation of moisture content in combinations of bait materials and bait stations Bait preparation. Bait sources viz., coconut leaves, paddy straw were collected, shade dried, cut into small pieces and grinded to fine powder. The food baits were prepared by mixing the respective bait constituents as in Table 1 with 0.50 grams of dextrose (binding agent). Based on the need water was added to the ingredients and hand moulded to compact discs (Fig. 1). For cut baits, the dried coconut leaves were chopped to about 5-7 cm length, and directly used as bait without adding other ingredients. Bait stations. To protect the food baits, suitable bait stations were selected viz., mud pot, plastic container, plastic sachet and 5-6 holes were made in the selected bait stations to facilitate the termite movement, foraging, tunnelling activities and for air circulation (Fig. 2). Based on the bait and bait stations the following treatment combinations were formulated. Treatment details: Field simulation and moisture estimation. Soil was collected from the fields before irrigation and filled in the polypropylene trays. The bait along with bait stations as per the treatment details were placed to simulate the field condition for moisture estimation. Initial weight of the bait before placement and the weight at 3rd, 5th, 7th, 9th, 11th, 15th day after placement (DAP) were measured using the analytical weighing balance. Dry weight of the baits were measured after placing the baits in the hot air oven at 105°C until the constant weight is measured for three consecutive times. The moisture content of the baits were calculated on the wet basis using the formula, Moisture % = B. Studies on field evaluation of bait materials Coconut leaf bait, paddy straw bait, combination bait and cut bait were prepared as mentioned above and placed in the termite active coconut gardens which constitutes 4 treatments viz., T1 – Coconut leaf bait, T2 – Paddy straw bait, T3 – Combination bait, T4 – Cut bait. Plastic containers were used as the bait station in all the treatments. Each treatment was replicated five times. The termite population was recorded on 3rd, 9th, 15th and 21st DAP. The initial weight of the bait before placement and the final weight of the bait at 21 DAP were measured for calculating the feeding percent. Feeding percent = Statistical Analyses. Percent data and population numbers were subjected to arcsine and square root transformation respectively prior to analysis to stabilise the error variance. Complete randomised design (CRD) was used to analyse data from the lab experiment (Moisture content estimation) and randomised block design (RBD) was used to analyse data from the field experiment. The data were subjected to one way ANOVA and means were separated using Duncans Multiple Range Test (DMRT) in the SPSS Software (Gomez and Gomez 1984). RESULTS AND DISCUSSION A. Studies on laboratory evaluation of moisture content in combinations of bait materials and bait stations Among the different bait and bait station combinations, coconut leaf bait retained higher moisture content followed by paddy straw, combination and cut baits (Table 2). The coconut leaf bait placed in plastic sachet had 52.12% moisture comparatively higher than that of those placed in plastic container 50.61%. It was evident that the tunnelling activity of termites was mostly reliant on soil moisture (Kushwanto et al., 2015). The results from laboratory investigations of Su and Puche (2003), demonstrated that the presence of sound wood had little effect on tunnelling activity and on the other hand positive moisture gradient boosted up the tunnelling activity of the termites. Higher the moisture content, increases the foraging activity of termites. Compactness, less aeration and more water droplets were recorded on baits placed in the plastic sachet. The water droplets in the sachet may affect the tunnelling of termites which in turn would affects its reunion with their nestmates. This concept is in line with the studies of Xie et al. (2019), that the tunnelling and feeding behaviours of the termites were restricted in the more water saturated condition. Hence the coconut leaf bait with plastic container retaining 50.61% moisture content used for field evaluation. Webb (2017), observed better foraging activity in field installed plastic bait stations. The plastic stations would be durable and maintains an undisturbed microenvironment for the termites (Quarles, 2003). B. Studies on field evaluation of bait materials Among the food baits in the plastic bait station, the highest number of termites (Odontotermes sp.) 843.4 were recorded in coconut leaf bait (T1) on 15th DAP followed by combination bait (T3), paddy straw bait (T2) and cut bait (T4). Feeding percentage of the baits also followed the similar trend, T1 (73.99) > T3 (68.26) > T2 (69.46) > T4 (31.37). Termite population was highest at 15 DAP, after which it started to decrease gradually (Table 3). The foraging activity of termites on coconut leaf and paddy straw bait is due to the presence of cellulose as its main constituent. The paddy straw and coconut leaf let constitutes approximately 36 % and 45.58% cellulose respectively (Bakker et al., 2013; Rajendra, 2019). The result corroborated with the findings of Lenz et al. (2009), wherein the presence of more cellulose supply was critical for termites to consume more matrix especially when alternative sources were available. Sandeep Singh (2020), revealed that the termite foraging activity is attributable to the presence of cellulose content. Among the wood constituents, cellulose is particularly attacked by the termites with the co-efficient of utilization ranging from 74% to 97% (Seifert and Becker, 1966). The present study also gains the support of Krishna and Weesmer (1969), who reviewed that the termites get their energy primarily from cellulose. The nutritional regime of termites has not changed significantly over time yet, it primarily constitutes the higher cellulosic materials.

How to cite this article

S. Sathyapritha, K. Premalatha, P.S. Shanmugam, S. Harish, S.V. Krishnamoorthy (2022). Comparative Evaluation of Bait Materials and Bait Stations for Subterranean Termites. Biological Forum – An International Journal, 14(2a): 453-457.