The Phenacoccus solenopsis

Already reported in India and Pakistan as Cotton mealy bug which is scientifically named Phenacoccus solenopsis was identified for the first time in Sri Lanka by the Department of Zoology of the Eastern University. This mealy bug was also first observed and studied in June 2008 in a study of mealy bugs attacking home garden plants.

Around June 2008, a new invasive mealy bug was identified from the Western Province which later identified as Papaya mealy bug (Paracoccus marginatus). It attracted the attention of the media and the public. Following this, another exotic insect species which mainly attacks the Shoe flower Hibiscus rosasinensis.

The cotton mealy bug doing its duty

In addition to Shoe-flower plants, Phanacoccus solenopsis mainly attack Brinjal, okra, chilli, tomato and some other crops, ornamental plants and weeds of families Malvaceae and Solanaceae. Worldwide the P. solenopsis is known to attack plant species from 31 families. Phenacoccus solenopsis was described originally from the US in 1898 and it remained known only in the US, where it is widespread, until 1992.

In 1992, it was reported in Central America, the Caribbean and Ecuador. In 2002 it was recorded as a pest of Solanun muricatum in Chile and its first record from Brazil was in 2005, India in 2006. Recently (in 2007) it became a serious threat for the cotton cultivation in Punjab and Gujarat of India.

It is observed that the infestation of cotton mealy bug begins in shiny period following a rainy season. It flourishes within 3-4 weeks and became a serious pest and destroys completely the nursery stocks and small plants. Infection and fast spread is observed in the dry season with a moderate wind action and low rainfall.

The cotton mealy bug belongs to the order Hemiptera, Suborder (Sternorrhyncha) and the family (Pseudococcidae) and these are plant sucking insects. Pale yellow, 3-6mm length adult female produce hundreds of first stage young by ovoviviparity (eggs hatch inside female body giving birth to living young). The adult female body is covered with whitish waxy secretion and has a pair of exclamation mark on the dorsal head region and three pairs of black markings on dorsal thoracic region of the body.

The first instar nymphs (first stage young) named crawlers have high dispersal ability and they find their hosts by themselves. In addition, infected plants and plant parts may transport these crawlers to various places including through export commodities to other countries.

Host plants that are affected by mealy bugs show curled leaves some times with bunchy tops. Flowers and fruits drop off without maturity and mostly nursery plants die off due to the infestation of this mealy bug. Cotton mealy bugs secrete honey dew (a surgary solution) which attract ants and they have an association with the ants. Ants are also the transporting agents of the mealy bugs to different host plants. Fungi grow on the plants as they have honeydew the food source for the fungal growth.

Natural predators of this cotton mealy bug were observed during the study. Predatory instars of lady bird beetles, green lace wing larvae feed on the mealy bugs of all stages and tiny parasitic wasps kill the mealy bug by laying eggs in it.

Present observations reveal that the attacks is not above the threshold level in the agriculture field crops. But the home gardens are mostly affected. Infestations are high in certain periods and some level of natural control is achieved through the natural enemy population and by the intermittent rainfall. In future climatic changes and favourable environmental factors may lead them to flourish in the home gardens and can become a major pest of field crops.

Therefore, close monitoring and proper management of the pest is paramount important. This article aims to report the first record of the alien invasive mealy bug species from the Eastern region of Sri Lanka and to create awareness among the public regarding this pest.

M. Prishanthini and Dr. (Mrs) M. Laxmi Vinobaba, Department of Zoology, Eastern University, Sri Lanka