Timbuktu or to study. By 1300, the population increased to 10,000 and kept increasing until it reached about 50,000 in the 1500s. There is insufficient rainfall in the Timbuktu region for purely rain-fed agriculture and crops are therefore irrigated using water from the River Niger. The main agricultural crop is rice. African floating rice ("Oryza glaberrima") has traditionally been grown in regions near the river that are inundated during the annual flood. Seed is sown at the beginning of the rainy season (June–July) so that when the flood water arrives plants are already in height. The plants grow up to in
Scirpophaga nivella orange anal tuft, sometimes brownish in the female. The larvae are off white with a reddish dorsal line. Major feeding plant is sugarcane, besides "Oryza sativa", "Scirpus", "Cyperus", "Eleocharis" (including "Eleocharis dulcis") and "Calidum articulatum" are also susceptible as feeding plants of the moth. Caterpillars bore into midrib, by leaving red markings and small holes on the leaves. Then it bore in the upper portion of stem, causing "dead heart" symptoms. Gradually, side branches start growing from a lower node, giving a characteristic "bunchy top" appearance to the plant. Most effective method is using biological predators and parasitoids. It is