Biological control can be achieved by growing a Desmodium (tick-trefoil) undercrop (see push-pull technology). The trefoil can be used as green manure or animal fodder after the harvest.In the USA, witchweed was discovered in the Carolinas in 1955. It is considered an invasive agricultural pest, and a vigorous eradication campaign has reduced the affected area by 99% [from 450,000 acres (1,820 km2) to about 3,400 acres (14 km2)].Striga asiatica, the Asiatic witchweed, is a hemiparasitic plant in the broomrape family. It is native to Asia and sub-Saharan Africa, but has been introduced into other parts of the world including Australia and the United States. Witchweed is a serious agricultural pest as it parasitises important crop species, including corn, rice, sorghum, and sugar cane, often causing substantial yield reductions.
Native To: Africa and Asia
Date of U.S. Introduction: First identified in North Carolina in 1956
Means of Introduction: Accidental
Impact: Parasitic plant that attacks agricultural crops, including corn, sorghum, sugarcane, and rice
Description S. asiatica seedlings are not visible above ground, but white succulent shoots can be found attached to host roots. Mature plants have green foliage above ground and that is sparsely covered with coarse, short, white, bulbous-based hairs. are normally 15-30 cm tall but have grown to 60 cm. Leaves are nearly opposite, narrowly lanceolate, about 1-3 cm long, with successive leaf pairs perpendicular to one another. flowers in summer and fall. Flowers are small (less than 1.5 cm in diameter) are sessile, axillary, the corolla is two-lipped, and they occur on loose spikes. Flower colour varies regionally, from red, orange, or yellow in Africa to pink, white, yellow, or purple in Asia. The flowers give way to swollen seeds pods, each containing thousands of microscopic seeds. Underground stems are round with scale-like leaves and white but turn blue when exposed to air. The roots are succulent, round, without root hairs, and found attached to a host species root system.