Bioassay
The test material was sprayed or painted on the
primary leaves of 5 to 6-days-old cowpea plants (see
Fig. 4). After 24 h the leaves were dusted with carborundum
powder which served as an abrasive to
allow inoculation of the TSWV strain. After 5 minutes
the excess inoculum was washed off the leaves. Local
lesions developed after 3-5 days were counted, and
the percentage inhibition calculated. Water, instead
of test material, was applied to control plants.