- Some varieties of sorghum such as Gubiye, Framida, Dobbs and Radar, and a few
sugarcane varieties have some resistance to Striga. Purdue University has been
active in developing and distributing a number of Striga resistant varieties. Maize
resistant varieties are being developed at IITA, Nigeria.
Striga in Seed
Rapid check for presence of Striga seed in a sample:
Put a random sample in a plastic bag, stand the bag upright and agitate/shake the bag as
often as possible over a 24 hour period. While still upright, remove the upper 75% of
seed. Examine the lower 25% for a brownish dust/powder. If present (if possible,
inspect under a hand lens or microscope), reject the lot for seed. If absent, the whole lot
can be used for seed, or, to be more careful, use only the upper part for seed and the
lower part for food.
More precise check for presence of Striga seed in a sample:
Sow the sample in a field known to be free of Striga, or in sterilised soil. In about 45
days the Striga will show itself.
Herbicides
Detailed technical information is available in the PNW Weed Management Handbook
(available online).
Herbicides, or weedkillers, are chemicals that kill or damage plants by their
phytotoxic properties. Their method of action is either selective—killing or stunting
only weeds and leaving the crop undamaged (eg MCPA and 2,4-D) or total (non-
selective)—killing or stunting all vegetation (eg Paraquat and Diquat /Reglone).
Some observations on Herbicides
- In general, seedlings and young plants are more susceptible to herbicides than
mature plants. - Some “total” herbicides become “selective” when they are diluted sufficiently.
- Even the so-called selective herbicides can have some negative effects on the
growth of the crop, and so are normally used at low concentrations. - Both selective and total herbicides can be applied either as foliar sprays (the
contact or translocated sprays), or directly onto the soil where they have a residual
effect. - Some herbicides, normally the selective ones, are available in granular form.
- 2,4-D and MCPA are taken up (translocated) by plants very strongly, and very
small quantities can damage certain sensitive crops such as coconuts and palms.
Types of Herbicides
then worked into it where they persist and so kill weeds as they grow or germinate.
90 TONY WINCH
- Residual—mainly for the control of perennial weeds. They are applied to the soil and
2.Contact—scorch, stunt or kill nearly all parts of the plant that they touch. They often
do not kill perennial weeds, but just slow down their growth. They are normally