Pests, diseases and crop protection practices in the smallholder sweetpotato production system of the highlands of Papua New Guinea

Abstract

Sweetpotato (Ipomea batatans) is a food crop of global significance. The storage roots and foliage of crop are attacked by a wide range of pests and diseases. Whilst these are generally well controlled in developed countries using approaches such as clean planting material and monitoring with pheromone traps to guide insecticide use, research into methods suitable for developing countries has lagged. In Papua New Guinea (PNG), sweetpotato is grown extensively as a subsistence crop and commercial production as a cash crop is developing. We report results from a survey of 33 smallholder producers located in the Highlands of PNG where the crop is of particular importance. Surveys of interviewees’ crops showed high levels of pest and disease impact to foliage, stems and storage roots, especially in crops that were several years old. Weevils (Curculionidae) were reportedly the most damaging pests and scab (caused by the fungus Elisnoe batatus) the most damaging disease. Most producers reported root damage from the former and foliar damage from the latter but the general level of knowledge of pest and disease types was low. Despite the apparency of pest and disease signs and symptoms and recognition of their importance by farmers, a large majority of producers reported practiced no active pest or disease management. This was despite low numbers of farmers reporting use of traditional cultural practices including phytosanitary measures and insecticidal plants that had the scope for far wider use. Only one respondent reported use of insecticide though pesticides were available in nearby cities. This low level of pest and disease management in most cases, likely due to paucity in biological and technical knowledge among growers, hampers efforts to establish food security and constrains the development of sweetpotato as a cash crop.

Screening barrier plants to reduce crop attack by sweet potato weevil (Cylas formicarius)

“…The amount of edible energy that can be produced per hectare is matched by few other crops and in some parts of the world, sweet potato is relied on to provide food when other crops fail . The high yield potential of sweet potato is often not realized in smallholder farming where poor knowledge of pests and a low availability of management options mean that little is done to manage pest attack . The sweet potato weevil, Cylas formicarius (Fabricius) is considered the most problematic pest of sweet potato as even light infestations can render roots unfit for human consumption .…”

“…This pest is effectively controlled by a combination of sanitation, insecticides and pheromone trapping in industrial agricultural parts of the world. These methods are less available and appropriate in developing countries, presenting the need for other, ‘low‐tech’ and affordable methods that can be used by smallholder farmers …”