Striga (Witchweed) Threats to Cereal Crops Production and Its Management: A Review

Nagassa Dechassa

doi:10.7176/alst/88-02

Abstract

Striga (witchweed) is one of the most successful parasitic weeds of cereal crops in Africa. It is ‘a poor farmer’s problem’ as there is a near perfect ecological overlap between areas of Striga infestation and where hunger prevails. It is originated in Semien hills of Ethiopia and the Nubian hills of Sudan and later expanded in about 42 African countries. Striga hermonthica, Striga asiatica, Striga gesnerioides, and Striga aspera constitute the greatest economic threat to cereal crops’ yield losses. They are obligate root parasites causing growth inhibition and yield losses of 20-100% in maize, rice, sorghum, pearl millet, finger millet, sugar cane and cowpea. Cultural practices such as long-term rotational cultivation of cereal crops with legume crops unaffected by the parasite is effective in managing the weed. Besides, biological control by use of parasitic fungi ( Fusarium oxysporum and Vesicular arbuscular mycorrhiza) play a role in managing the weed. In addition, chemical control with imidazolinone herbicide, ethylene gas, dicamba and 2,4-D are effective in managing striga in cereal crops in extreme cases. Integrated use of striga resistant crop varieties with water conservation practices, soil fertility amendment and use of parasitic fungi ( Fusarium oxysporum and Vesicular arbuscular mycorrhiza) is effective in control, economically safe, socially acceptable and environmentally friendly than a single control measure. Therefore, the promising integrated striga management practices should be highly promoted. Moreover, host and Striga species specific integrated Striga management should be designed. Keywords: Haustoria; Obligate parasite; Root parasite; Strigolactones; Witchweed DOI: 10.7176/ALST/88-02 Publication date: July 31 st 2021

Highlights

Parasitic weeds attack other plants by making networks and deriving portion or entire of their nourishment from their host
Root parasites (Striga spp. and Orobanche spp.) and shoot parasites (Cuscuta spp., Viscum spp. and Arceuthobium spp.) are the major threat to agriculture which cause the majority of yield losses [4]
Striga asiatica, Striga gesnerioides, and Striga aspera are the most wide spreading among 40 Striga species

Summary

Introduction

Parasitic weeds attack other plants by making networks and deriving portion or entire of their nourishment from their host. Striga Management by Cultural Practices The best practice is long term rotational cultivation of cereal crops with legumes or other crops unaffected by the parasite Cultural practices such as crop rotation, water management, early planting and use of early maturing varieties are effective in reducing striga seed banks in the soil, improving soil fertility, enhancing sorghum growth rate and retarding the parasites seed germination and seedling development [36]. Their poor adoption, high cost of implementation, high labor requirement and inapplicability of them on large fields are limitation of cultural striga management practices [36]. The sequential application of pre-emergence herbicide (Dual gold) and post emergence herbicide (2, 4-D) is effective against Striga weed in sorghum in Ethiopia [41]

Conclusions

Findings

The Way Forward