These results indicate that the acrylic resin, Rhoplex AC-33, when
used at one part adhesive solids to three parts methiocarb solids,
probably interferes with or masks the repellent properties of methio-
carb. They also suggest that adhesives should probably be omitted
from spray treatments in very dry climates, such as in Sudan, where
rains seldom fall during the season when sorghum heads are maturing.
If adhesives are needed, ratios of less than one part adhesive to
three parts methiocarb should be used. A 1:10 ratio is proposed for
further trials.

Field trials: Upper Nile, Blue Nile, Kordofan, and Kassala Provinces

Several field trials and cage studies were conducted to further evalu-
ate the effectiveness of repellents as a means of reducing quelea
damage to sorghum. The results of these studies are summarized here.

1. The effective level of methiocarb for protection of dura (sorghum)
against quelea is less than 0.5 kg/feddan when sprays are directed at
the heads only. A plant population of 10,000 plants/feddan was
assumed for this calculation. This is probably near optimum effec-
tiveness as 'the residue level at this concentration was computed to be
about 65 parts per million (ppm). Each 60-g head was treated with
5 cm3 of a 0.09-percent methiocarb suspension with about 90 percent
retention of spray.

2. Methiocarb applied to dura heads at levels computed to be about
200 ppm (a 0.27-percent spray) was lethal to about one-fourth of caged
quelea and nearly one-half of caged masked weavers, clearly indicating
that lower levels would adequately protect dura. A 1-percent level on
flowering dura was highly lethal to fasted red bishops which were
taking an average of about five seeds, again indicating that much
lower levels would give effective repellency.

3. A 1-percent Avitrol spray on dura heads is lethal to quelea taking
one to three seeds from heads just beyond the flowering stage.
Slightly higher levels may be needed for late-dough-stage sorghum
where only the germ may be taken. A ratio of 10 heads/feddan
(1:1,000) is apparently too low for effective protection, unless
flock response is obtained and large numbers of quelea are involved.

4. In mist-netting birds for enclosure experiments, it was soon
discovered that quelea, masked weavers, and red bishops could be
taken in substantial numbers. From 25 to 100 birds were taken per
net hour from populations not exceeding 2,000 birds.