Chapter 15 - Phalaris minor and Phalaris paradoxa

Abstract

The genus Phalaris (Poaceae) is comprised 21 species, which is distributed in temperate areas of both northern and southern hemispheres and the mountains of tropical Africa and South America. Phalaris minor and Phalaris paradoxa are highly competitive weeds in winter cropping systems involving cereals, pulses, pastures, horticultural, ornamental crops, and vineyards. Both species produce a large number of seeds with varying forms of dormancy, although their half-life in the soil seed bank is relatively short. The yield losses in wheat due to P. minor and P. paradoxa may be up to 50% and 40%, respectively. Both species are prolific seed producers, short-lived, and exhibit periodicity of emergence. With the increase in concerns about the environment and human health issues, there is a greater emphasis on predicting the emergence pattern of weed species in relation to soil environmental conditions. The cornerstone for effective weed management relies on various aspects related to seed germination, dormancy, viability, loss of vigor, and resultant seed bank dynamics and its distribution pattern in the soil. In this chapter, we described biology and ecology along with molecular, physiological, and agronomic aspects involved in herbicide resistance observed in biotypes of these weed species. New selective herbicides are needed to augment those currently available to overcome present and future resistance problems. Integrated weed management strategies involving herbicide rotation and/or mixture with different modes of action and other cultural control measures will help to reduce selection pressure and prevent further spread and evolution of herbicide resistance in Phalaris species across different continents.