Weed control is necessary until the taro leaf canopy has closed
Taro crops are affected by a number of weeds, insect pests and diseases.
Newly planted taro crops are susceptible to competition from weeds, so weed control should be carried out after planting. However, weeds are generally not a problem once the leaf canopy has closed. Further weed control should be carried out towards the end of the life cycle as the crop matures, as this is a critical period for starch accumulation.
Plastic mulching can provide a barrier to growing shoots and corms. Care should be taken when spraying around taro plants, as there have been instances of chemical damage to taro plants as a result of spray drift from adjoining properties.
Numerous insect pests have been recorded in the Pacific region, but few have been identified in North Queensland, where taro is still a relatively new crop.
Many chewing insect grubs feed on the rich, starchy corm. Cluster caterpillars can present a major insect problem in taro crops, as they strip the upper surface of the taro blade. The eggs are laid in clusters and are covered with fine hair-like scales. The mature caterpillar is about 45 mm long, and appears grey with a green underside. It has a pale stripe and a series of dark spots along the sides. The young caterpillars of the hawk moth can also cause significant damage by making holes in and defoliating the leaves.
Although various beetles feed on taro, none have been specifically identified as taro beetles.
Erwinia soft rot is caused by Erwinia atroseptica. The corm becomes mushy and smelly and the affected plants eventually wilt and die. The condition appears to be exacerbated by high organic matter, particularly in areas previously under pasture. The presence of chewing insects - for example, the white cane grubs in North Queensland cane lands - also contributes to the problem.
Shot hole leaf disease is a common fungal disease in the wet tropical coast of North Queensland. The disease is worse during wet weather and in closely spaced plants. Initially, small, dark spots appear on the leaves, then, as these spots increase in size, the centre of most spots falls out. The leaves become unmarketable and the reduction in photosynthetic area can cause substantial reduction in corm yield.