Parthenium hysterophorus L. is a noxious weed commonly called carrot weeds and become worst weed of urban and rural areas of Nepal. It is considered one of the world’s most invasive weed. Contact with this plant causes dermatitis and respiratory malfunction in humans, dermatitis in cattle and domestic animals, due to the presence of toxin parthenin. This foreign weed is increasingly becoming a problem in road sides, protected forest, pasture and fallow land in Nepal. Now it is found all areas of the country from east to west and terai to hills. The weed was believed to be come in Indian subcontinent via wheat seed in 1950s from USA. In India, it is locally known as Congress Grass or Gajar Ghans. It was first present as a contaminant in imported wheat. It can trigger allergies and is a common cause of pollen allergy. This weed dispersed all-round the country and become matter of headache for farmers, scientists, ecologists, medical and veterinary practitioners due to it's wide spread effect in farming system, bio-diversity, human and livestock health.
Zygogramma bicolorata Pallister is an important bio-control agent of this weed. It was first introduced to India in 1984 from Mexico that's why also known as Mexican beetle.
Mr. Ram Bahadur Khadka, Scientist, Regional Agriculture Research Station (RARS), Khajura, Nepalgunj, Banke, Nepal in his schedule of technical visit found the Mexican beetle at Gulariya Municipality, Bardiya, Mid-Western Nepal, at completely defoliated parthenium plants in April 26, 2014 and about 7 copulating pairs of adult beetles were collected in plastic container and kept in the adult parthenium plants making cage around it at the station in Khajura. The beetles have completely defoliated the plants inside the net and population was increased upto1000. Now it has been maintained in glass/ screen house with relay cropping of parthenium once after defoliation.
Beetles have completely defoliated the parthenium plants as in photo. This is an encouraging result of works carried out by Mr. Khadka which in future would help to control parthenium biologically through rearing Mexican beetles and releasing them in parthenium affected areas and around.
Figure 1 Mexican beetles defoliating parthenium plants
Figure 2 Mexican beetle in parthenium plant
Figure 3 Beetles defoliating the parthenium plant
Figure 4 Mexican Beetle