Government Agricultural College, Ludhiana (Punjab)
Pieria brassicae L. is the commonest and the most abundant of all the Pieris species and generally predominates in Europe and Asia. In India it has been recorded from U. P., Bengal, Bihar, Assam, Himachal Pradesh and Punjab, where it is found practically in all the district growing cruciferous crops. It has been found damaging cabbage, cauliflower, radish, turnips, Karam sag, (Brassica sp), raya, (Brassica juncea), sarson (Brassica a -npestris) tara mira (Ervca sativa) and Nasturtium indicum.
The eggs are laid in clusters both on the upper and lower surfaces of the leaf, each cluster containing 50–80 eggs. The eggs hatch in 3.2±0.02 to 17.6±0.16 days in different months. The young caterpillar on hatching first feeds on its own egg shell and then starts feeding on the leaf. Caterpillars stage occupies 15.6±0.03 to 40.7±0.89 days in different months, during which period it moults four times. The caterpillars usually remain gregarious except when forced to disperse due to scarcity of food. Under normal conditions, they disperse towards the end of the fifth instar for finding suitable places for pupation and travel 70–80 yards. Pupation takes place on the leaves and stems of trees, dark corners of verandah etc. and rarely on the host plants. The pupal stage is completed in 7.3±0.03 to 28.8±0.2 days depending upon the season. Mating takes place end to end and lasts for 60–95 minutes. The female starts laying eggs in clusters at the rate of 4–5 eggs per minute the next day after copulation. The adults live for 2.6±0.03 to 12.3±0.76 days in different months.
The first instar caterpillars just scrape the leaf surface whereas the caterpillars of the subsequent instars consume the lamina either along the border or bite big holes in the leaf. As a result of its attack, the leaves are skeletonised and only the veins are left behind. The caterpillars have also been observed to bore into the heads of cabbage and render them unmarketable. In the gardens, the nasturtium plants are entirely denuded their leaves.
