Innovations in parasitic weeds management in legume crops. A review

Abstract

Parasitic weeds decrease severely the production of major grain and forage legumes. The most economically damaging weeds for temperate legumes are broomrapes, in particular Orobanche crenata. Broomrape species such as Orobanche foetida, Orobanche minor, and Phelipanche aegyptiaca can also induce high local damage. Other parasitic weeds such as Striga gesnerioides and Alectra vogelii decrease yield of legume crops throughout semi-arid areas of sub-Saharan Africa. Dodders such as Cuscuta campestris can be damaging for some crops. Here, we review methods to control parasitic weeds. Preventing the movement of weed seeds into uninfested areas is a crucial component of control. Once a field is infested with parasitic weeds, controlling its seed production is very difficult. The only effective way to cope with parasitic weeds is to apply an integrated approach. Seedbank demise can be achieved by fumigation and solarization. However, this method is not economically feasible for low-value and low-input legume crops. A number of cultural practices including delayed sowing, hand weeding, no-tillage, nitrogen fertilization, intercropping, or rotations can contribute to seed bank demise. Other strategies such as suicidal germination, activation of systemic acquired resistance, biocontrol or target site herbicide resistance are promising solutions that are being explored but are not yet ready for direct application. The only methods currently available to farmers are the use of resistant varieties and chemical control, although both have their limitations. Chemical control with systemic herbicides such as glyphosate or imidazolinones at low rates is possible. Advances in modeling and the availability of new technologies allow the development of precision agriculture or site-specific farming. The most economical and environmentally friendly control option is the use of resistant crop varieties; however, breeding for resistance is a difficult task considering the scarce and complex nature of resistance in most crops. These strategies for parasitic weed management in legume crops will be presented and critically discussed.