2.3. Development and survival of immature P. xylostella
Before the experiment, P. xylostella was reared for one generation
on each host plant to eliminate the effect of food reserves in
the eggs and neonate larvae. To test the effect of host plants on the
development, P. xylostella adults (3 days old) were taken from the
corresponding host species and maintained in a cage
(60 60 60 cm) screened with white nylon organdy (100 mesh).
The adults were allowed to mate and oviposit. Newly laid-eggs
(12 h old) were individually placed in a leaf clip-on cage (1 cm
in diameter and 1 cmin depth) on the lower leaf surface using a soft
brush. When the larvae grew to third instar, the small clip-on cage
was changed to a larger one (3.5 cm in diameter and 1.5 cm in
depth). Each clip-on cage containing one egg (or larva) was
considered one replicate, so there were 50 replicates per host plant
species. The eggs or hatched larvae were observed daily until they
died or developed to adults. The data recorded included larval
hatching, developmental duration of each larval instar, and pupal
stage. The sexes of the emerged adults were recorded.