Common names: 

Pest status:

Distribution:

Mopane bagworms were observed on nearly every mature mopane tree in the four regions, stretching from Eunda in the west to Ondobe in the north east. (It was not sought further east). Along the road from Oshakati via Okahao and Tsandi to Outapi, the bagworms were found a few kilometres west of Okahao and then all the way to Outapi. On the Ondangwa-Tsumeb road it was very common from Oshakati through Ondangwa until Onankali, after which there are no longer mopane trees along the road.

Mopane bagworms were NOT found on any young mopane growth, e.g. mopane trees that regrow after having been coppiced. 

Description:

As soon as the first showers signal the beginning of the rains (November-December) the eggs hatch and hundreds of tiny caterpillars disperse from the mother bag. These caterpillars are naked to begin with but witin a few hours they have gathered enough leaf material for a small cone that can cover them. The material is taken from epidermis of the leaf but the damage is hardly visible. At this stage the cones are whitish or pale green.

The attack is first noticed as small spots, scattered over the mopane leaves. The spots are about 5 mm in diameter and they eventually turn red-brown. Only the epidermis is eaten so there are no holes through the leaf. The small caterpillars can be found in small cone-shaped bags made of green leaf material. The caterpillars spend the rest of their life in such bags that just are expanded when the caterpillars grow bigger. They can move easily by strecthing their heads out through an opening in the top of the bag and pull the bag to a new place on the leaf.

The attack develops throughout the rainy season. The caterpillars grow bigger and increase their feeding as well. Soon entire leaves have no green parts left  for photosynthesis (see 2 above). The leaf colour changes from fresh green to bronze or brown. The attack can be seen from a long distance, as the lower half of the tree crowns are entirely bronze or brown in colour while the upper half is the natural green colour (see above).

When the caterpillar reach the final stage and the bag is about 5-6 cm long it stops feeding and ties the bag firmly to a small twig or to the trunk of the tree. The bag is sealed tightly and the caterpillar pupates insite and waits for suitable wether before emerging as an adult moth. These mature bags are often much darker or more grey than young fresh bags, and they are found in large number under main branches on mopane trees.

At time of hatching, the (male) pupae wriggles out through the bag and the moth leaves the bag. Empty pupae skins are easily noticed as dark brown cylinders protruding half a centimetre out under the bag.
 

Control:

Other notes:

During December 2000, one hundred bags of bagworm were picked from a tree in Oshakati. They were brought in for rearing and I began to sprinkle water over them in the hope that they (the males) would hatch. A few days later the eggs inside the bags hatched instead and thousands of tiny black dots started moving around in the cage until they were given fresh mopane leave to gather on. They quickly began to "graze' the epidermis and soon each of them had gathered a little cone of pale green mopane leaf material.

I must conclude that the male moth flies and mate during the rainy season when the bagworms have reached maturity. The female then lays eggs inside the bag and both female and male die. The dormant stage is therefore the eggs and not the pupae.

Investigations will continue. Please contact me if you have more information about the Mopane Bagworm or  you would like to participate in the investigations.