Sorghum halepense (L.) Pers. is ranked among the worst and extensively disseminated weed species. It is emerging as a potential menace for agroecosystems in 53 different countries across the world. This weed is adapted to warmer regions and is native to Mediterranean areas of Africa, Asia, and Europe. In the mid-1900s, cultivation of this weed species as a potential forage crop resulted in its escape from crop fields and invasion of agricultural and natural areas, but in some European countries, it has been introduced deliberately (e.g., as contamination of seeds and soil). S. halepense interferes with economically important agronomic and horticultural crops and cause 57-88% yield losses. Herbicide tolerance, diverse propagation mechanisms, rapid development, and strong competitiveness are key attributes in its invasion. Conventional management approaches are limited in their scope to control this weed due to its rapid vegetative growth and increasing herbicidal tolerance. Integration of chemical methods with cultural or mechanical approaches is important for restricting its future spread to non-infested areas. This review provides insights into the invasion mechanisms of S. halepense, which will help in its

Avena fatua and Avena ludoviciana are closely related grass weed species infesting a large number of crops around the world. These species are widely distributed in diverse agro-ecosystems from temperate to sub-tropical regions due to their unique seed traits, successful germination ecology, high competitive ability, and allelopathic potential. A. fatua is more widespread, adaptable, and problematic than A. ludoviciana. Both these species infest major winter and spring crops, including wheat, oat, barley, canola, maize, alfalfa, and sunflower, causing up to 70% yield losses depending on crop species and weed density. Chemical control has been challenged by large-scale herbicide resistance evolution in these weed species. A. fatua is the most widespread herbicide-resistant weed in the world, infesting about 5 million hectares in 13 countries. The use of alternative herbicides with different modes of action has proved effective. Several cultural practices, including diverse crop rotations, cover crops, improved crop competition (using competitive cultivars, high seed rates, narrow row spacing, altered crop geometry), and allelopathic suppression, have shown promise for controlling A. fatua and A. ludoviciana. The integrated use of these cultural methods can reduce the herbicide dose required, and lower dependency on herbicides to control these grasses. Moreover, integrated management may successfully control herbicide-resistant populations of these weed species. The use of integrated approaches based on the knowledge of biology and ecology of A. fatua and A. ludoviciana may help to manage them sustainably in the future.

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Three C 4 grass (Setaria incrassata, Astrebla squarrosa and Bothriochloa decipiens) and one C 3 legume (Clitoria ternatea) suppressive fodder species, were re-evaluated against the growth of the C 3 Parthenium hysterophorus under an ambient (390 lmol mol À1 ) and an elevated atmospheric CO 2 concentration (550 lmol mol À1 ). Under the elevated atmospheric CO 2 , shoot dry biomass and suppression index (SI) value of the C 4 S. incrassata were both reduced by 32% and 0.7 respectively, while those for A. squarrosa were reduced by 23% and 0.3. In contrast and under the same elevated atmospheric CO 2 concentration, the shoot dry biomass and SI of the C 4 B. decipiens were increased by 8% and 0.1 respectively, while those for the C 3 C. ternatea were increased by 38% and 0.8. Our results suggest that C 3 fodder plants along with certain C 4 species could be utilised for the effective management of P. hysterophorus under the future elevated atmospheric CO 2 conditions. However, this system needs more fodder species to be investigated. Our results suggest that rising CO 2 per se may alter the efficacy of suppressive fodder management of an invasive C 3 species, P. hysterophorus.

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