Biological Control
Organisms considered to have potential as biocontrol agents for S. asiatica and/or other Striga species have included the gall-weevil, Smicronyx spp. the agromyzid fly, Ophiomyia Strigalis, the moths, Eulocastra argentisparsa and Eulocastra undulata, the plume moth, Stenoptilodes taprobanes, the powdery mildew Sphaerotheca fuliginea and other fungi including Drechslera longirostrata, Phoma and Cercospora species (Greathead, 1984). Evans (1987) considered Cercospora strigae the most promising of the fungi. Several different species of Fusarium have been shown to have potential against both S. hermonthica and S. asiatica (Abbasher et al., 1995;1996). None of these organisms have yet been successfully utilised, but the possibilities for using Fusarium oxysporum are still considered promising (Beed et al., 2007). The strain Foxy 2, widely tested on S. hermonthica is confirmed also to be active against S. asiatica (Elzein et al., 2002). More virulent strains are now being tested along with a novel means of on-farm culturing and it is hoped there could be commercialisation before too long (Koltai, 2015). The only attempts to control S. hermonthica have been with the introduction of Smicronyx albovariegatus and Eulocastra argentisparsa from India into Ethiopia in 1974 and 1978, but there is no evidence that these organisms ever established.
Has Cabi datasheet ID
51786
Detection
Where infestation is suspected, from previous history or from unexpected wilting symptoms, uprooting the crop can reveal the small white seedlings of S. asiatica on the roots, but the attachments are very fragile and gently washing the roots out of the soil will ensure a better chance of finding them.
A technique for detecting the seeds of S. asiatica as contaminants of crop seed is described by Berner et al. (1994). This involves sampling the bottom of sacks, elutriation of samples in turbulent flowing water and collection of seeds and other particles on a 90 µm mesh sieve. Striga seeds are then separated from heavier particles by suspension in a solution of potassium carbonate of specific gravity 1.4 in a separating column. Sound seeds collected at the interface are then transferred to a 60 µm mesh for counting.
