Zygogramma bicolorata Pallister: Feature beetle for biological suppression of Parthenium hysterophorus
Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae) a parthenium beetle or Mexican beetle is a small beetle having brown head, brown and yellow elytra marked with characteristic elongated brown stripes. Zygogramma bicolorata adult and larva are used as a bio control agent for controling Parthenium hysterophorus (Linnaeus) a weed commonly known as carrot grass, congress grass or gajar ghas, basically the origin of parthenium is considered to be Mexico, America, Trinidad and Argentina. Zygogramma bicolorata an exotic beetle introduced in 1983 from Mexico to Bangalore the beetles became established in most part of the South India and many parts of the Central and North India. Since It has become widespread and well-established on the subcontinent. It defoliates, often kills the weed and damage to the young flowering tops & reduces seed production.
In 1910 the Parthenium weed was first brought to India as an ornamental plant but it is failed to establish but later on in 1950’s Parthenium was introduced in India along with imported wheat from United States of America under PL-480 Project. At present Parthenium has invaded about 35 million hectares in India. It is a nuisance on road sides, railway tracks, barren lands, waste lands, and industrial areas, on the sides of open drainage system and irrigation canals, besides invading agricultural crops, orchards and forest area. In some areas, heavy outbreaks have been ubiquitous, affecting livestock, crop production and human health. It mainly spreads through seeds and single plant can produce about 5,000 to 25,000 seeds. Seeds are very small and light in weight so easily transported by wind water or through various human activities. In general, Parthenium is a poisonous, pernicious, problematic, allergic and aggressive weed posing a serious threat to human being, livestock and also causes several other problems. The plant produces dangerous toxic allelopathic chemical called parthene that suppress crop, plants and allergens that affect humans and livestock. It is also responsible for bitter milk disease in livestock when their fodder is polluted with Parthenium leaves.
Zygogramma bicolorata beetles feed on leaves, terminal buds and leaf blades of Parthenium and it is a promising bio control agent for contributing to control Parthenium effectively and economically without causing hazards to the existing ecosystem.