SNAIL INFESTATION ON MULBERRY (MORUS ALBA) IN HIGH WATER TABLE AREA OF KATHUA (JAMMU AND KASHMIR) DURING MONSOON SEASON

R.K.PANDEY and A. DHAR

Regional Sericultural Research Station, Miran Sahib, Jammu, E mail:  pandeyjammu@gmail.com

[A previous story written by RK. Pandey can be accessed HERE]

Snail is recognized by the Global Invasive Species Programme (GISP), as one of the 84 100 most destructive biological invasions in the world. This herbivore has a voracious appetite and is known to feed on over 500 species of plants (Simberloof, 2003). Apart from this, snail poses a potential health risk to humans, as some of its specimens are associated with an intermediate host of a nematode parasite Angiostrongylus Cantonensis, which is commonly known as the rat lung worm (Civeyrel and Simberloff, 1996; Carvalho et al 2003). This vector has the potential to cause eosinophilic meningoencephalitis and brain damage in humans (Upatham et al 1988).  From India, Thangavelu and Singh (1983) reported giant African snail as a serious pest of mulberry from north eastern region.  Shree and Kumar (2002) reported that snail infestation reduced moisture, proteins and starch content of mulberry leaves, but increased the content of phenols. Recently, Achatina fulica caused havoc in mulberry gardens of Ramanagram district especially in Kanakpura area (Kumar et.al.2011, Sreenivas et al., 2011).  Gopinath et.al (2013) has reported this snail infesting mulberry gardens in Tamil Nadu.  However, this is the first report on the occurrence of Zachrysia provisoria (Pfeiffer 1855)  in mulberry garden of Kathua in Jammu and Kashmir, particularly in area, where depth to water levels prevail less than 2meter during monsoon period between July and September.

A close view of Zachrysia provisoria  

Kathua lies at the southern most end of the state and is located between 34^o16’00” TO 32^o55’00” North Latitude and between 75^o06’ to 75^o54’ East Longitude. Various parts of the district experiences wide range of climate from sub-tropical to temperate and even Alpine in high regions of Bani. Due to altitudinal variations the plain areas of Kathua invariably differs in the temperatures from the hilly (Billawar and Bani) areas of the district. In Kathua, summer temperature rises as high as 48^oC and winter temperature falls as low as 3^oC in the plain. The district experiences rainfall during monsoon season and in winter and early summer. The average annual rainfall in the district is 1672 mm. About 85% of the total rainfall is received during monsoon season between July and September and rest occurs during December to February. Depth to water levels prevail less than 2m in and around Kathua plain area during the monsoon period, where the mulberry garden was established for silkworm rearing by the Research Extension Centre, Regional Sericultural Research Station, Miransahib,Jammu. About one year old saplings of an improved early sprouting Morus alba variety S146 were planted in the year 2001 under 3x3 feet spacing and bush type canopy was maintained by annual ground level pruning in monsoon period.  The snail infestation was noticed during the annual pruning operation in July 2002. Thereafter, observations were recorded for three continuous years up to 2005, regarding its seasonal infestation on mulberry. The snail Zachrysia provisoria was identified based on the basis of distinct morphology. In order to ascertain the density  of snail in the mulberry garden at Kathua, a 10 metre transect- with 2 x 2 m quadrats -  (each transect had 5 quadrats) was established.  Subsequent transects  were established every 10 metres. This process was repeated 8 times, giving the sampled area a total  of 40 quadrats (N=40) for the garden.  All individuals of snail that were in each quadrat were then counted, the weather condition was also recorded.

 Z. provisoria was very active during rainy season from July to September in Kathua. Heavy downpour for two to three days resulted in its outbreak. This snail spends most of his life time in dormant condition, especially during unfavorable climatic conditions. The shell of Z. provisoria is medium-sized (25 to 30 mm width), and globose in shape. There are four to five rapidly expanding whorls, with the body whorl increasing in size more than those of the spire. There is no umbilicus. The shell is sculptured with fairly regular, strong, retroactively curved axial ribs, and the body whorl descends greatly near aperture. The base is swollen, fairly smooth and shining. The apertural lip is thickened within, slightly reflected. There is a prominent protuberance or buttress on basal lip near columellar insertion.   It lives among leaf litter and among mulberry plants. Z. provisoria is a voracious herbivore and causes significant damage to mulberry. They were found very actively moving in marshy mulberry fields after dusk, eating voraciously mulberry leaves and even bark damaging epidermis and even vascular bundles, leading to weakening of stems. The shoot becomes fragile yellowish and collapse. The leaves lose their nutritive values and defoliate, causing considerable damage to mulberry plants in general and chawki garden in particular. The density of the snail per square meter was found to be 1.2 at Kathua in the rainy season. The snail was found to be nocturnal feeder but remained active during the day in cloudy rainy weather. In dry weather, it burrowed into the ground or crawled under shelter where it remained for several weeks or months. However, a survey of the district Kathua revealed that this snail was confined in areas where water table was near to the surface. No such snail infestation was recorded in Kandi plains and in higher hilly areas of Kathua district, where the ground water depth is more than 30 m.

Snail (Zachrysia provisoria) density in monsoon period in Kathua district

The snail may be of economic importance as a medicinal and nutritional protein source (Santos Carvalhoetal, 2003) but snail remains a serious agri-hortcultural pest throughout the Indo Pacific Islands (Raut, 1982). The snail presents possible public health hazards with regard to the spread of disease such as angiostrongylosis and eosinophilic meningoencephalitis due to its important role as a host in the life cycle of Angiostrongylus cantensis (CAB2003). Plant diseases such as black pod disease caused by Phytophthora palmivora are also spread through the faeces of the snail (Raut and Barker, 2002). Spray of salt water solution (4kg of salt in 10 liters’ of water) is found quiet effective in controlling snail. This study has indicated that Z. provisoria has successfully manifested and established itself within Kathua ecological community.

CONCLUSION

A terrestrial snail Zachrysia provisoria ( Pfeiffer 1855)  was found infesting Morus alba in high water table area, where depth to water levels prevail less than 2meter, of Kathua between July and September during monsoon period. However, no snail was found in Kandi and hill area of Kathua, where the ground water depth is more than 30 meters. This is the first report of snail pest on mulberry, which is cultivated in Jammu and Kashmir for Sericulture.

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