Striga

Striga, commonly known as witchweed, is a genus of parasitic flowering plants in the family Orobanchaceae. It acts as an obligate root parasite, severely compromising the health of many important cereal crops. By attaching to the host plant’s roots, it siphons off water, nutrients, and photosynthetic products, essentially causing the host to starve.

The primary hosts of Striga include major cereal crops such as maize, sorghum, millet, and rice. The pathogen's presence is often signaled by stunted growth, leaf chlorosis, and wilting, even when soil moisture appears adequate. Due to its physiological reliance on the host, Striga is classified as one of the most destructive agricultural threats in semi-arid environments.

The biology of Striga is unique due to its dependence on specific signaling molecules. The germination of Striga seeds is triggered by the secretion of strigolactones from the roots of potential host plants. Once these chemical signals are detected, the seed germinates and develops a haustorium, a specialized organ that penetrates the host's root tissue to establish a connection to its vascular system.

Environmental conditions greatly influence the spread and success of Striga. It thrives in low-fertility soils with high temperatures, often worsening the effects of nutrient deficiencies. A single Striga plant can produce over 50,000 tiny seeds, which remain viable in the soil for over a decade, making infestation management a long-term agricultural challenge that requires persistent intervention.

Control strategies for Striga must be multifaceted to be effective. Integrated weed management includes the use of resistant crop varieties, crop rotation with "trap crops" that induce germination without supporting the parasite's development, and the application of nitrogen fertilizers. Strict quarantine measures and the use of clean seeds are also essential to prevent the spread to non-infested fields.

• Obligate root parasite
• Severe impact on cereal yields
• Triggered by host strigolactones
• Long-lived dormant soil seed bank
• Requires integrated management