Striga
Weed
A
maize field Infested with Striga hermonthica
Striga
or witchweed are parasitic weeds that affects cereal
crops in many parts of Africa reducing production by
as low as 30% or as high as 100%. When a farm is infested
with Striga, the affected plants hardly grow more than
one foot tall. The weed does not grow on its own but
grows by attaching itself onto the host plants. Each
Striga plant can produce up to 20,000-50,000 seeds,
which lie dormant in the soil until a cereal crop is
planted again. This dormancy can last for over 15 years.
As striga germinates, it's roots grow towards the host
crop, penetrates that crop’s roots and starts to draw
nutrients from there. This causes severe stunting of
the host crop and yield loss.
In
East Africa, there are two common species of the witch
weed, Striga hermonthica and Striga asiatica. Striga
hermonthica is common around lake basin while Striga
asiatica is mainly found in the coastal areas. The most
affected crops include maize, sorghum, rice and sugarcane.
Taking
into account the peculiar nature of Striga seeds, farmers
are advised to control it before the weed emerges; the
reason being that by the time it emerges, much damage
will have been caused. Although various control methods
have been proposed, few farmers are able to avoid yield
loss by these means. For example, though manual removal
reduces re-infestation, it is deemed uneconomical since
most damage is done even before the weed emerges. Therefore,
any control strategy has to begin within the soil. If
maize plants are attacked by both stemborer and striga
weed, the yield loss could be 100%