An integrated pest management approach of amaranth insect pests in Buuri District, Meru County, Kenya Robert Nesta Kagali

Abstract

Production of amaranth is hampered by insect pests which reduce the yields considerably. The control of these pests is mainly through the use of pesticides, but their intensive usage has resulted in major environmental pollution and direct toxicity to humans, non-target insects and other mammals. Therefore, there is need to develop a pest control strategy that poses little or no risk to environment, man and other non-target organisms. The focus of this research was to identify amaranth pests and their natural enemies since correct pest identification forms the basis of any efficient integrated pest management. This research consisted of both ex-situ and in-situ experiments. The ex-situ research was conducted in Buuri District, Meru County where sampling was done using stratified random method. Surveys of insect pests were done on randomly selected farms from farmers who were growing amaranth in Meru County between April 2012 and April 2013 using Point-Centered Quarter Method to determine their diversity and abundance. The insects were collected by hand, sweep nets, knock down and pit-hole techniques depending on the type of insect. The effects planting dates, amaranth varieties, use of botanical pesticides on insect pest population were investigated on in-situ plots at Meru University College of Science and Technology. A total of 1256 specimens were collected, stored in alcohol, pinned on boards, identified and archived at National Museums of Kenya, Nairobi. Insect pests were classified into 5 orders, 15 families and 33 species with the most damaging insects being Cletus sp. (Heteroptera) which attacks the grain causing up to 40% loss, Hepertogramma bipunctalis (Lepidoptera) which feeds on stems and leaves resulting to 27% yield loss and Hypolixus nubilosus (Coleoptera) which also causes stem and leaf damage. The important natural enemies were grouped into 2 orders, 5 families and 8 species. There are diverse insect pests attacking amaranth causing considerable damage to yield of leaves, stems and grain hence requiring control measures. The insect pests caused a significant loss to the yield (P=0.0000112, F=13.67, n=24 and df =7, 16 during the first season and P=0.0000975, F=52.41628, n=24 and df=7, 16 during the second planting season) with a further separation of means showing a higher loss in plots with Amaranthus cruentus. All the pests groups resulted to a consolidated loss of 50% of the total yield with 49% being attributed to grain pests and 42.5% caused by stem and foliage pests. Neem (Azadirachta indica) leaf extracts are effective in the reduction of pest population and have little impact on the beneficial insects. Chemical control reduces the pest population considerably but reduces also the population of beneficial insects. A considerable number of naturally occurring enemies, parasites and parasitoids were collected indicating there is potential to conserve these insects for biological control. An effective integrated pest management strategy can be achieved with correct planting lines, use of botanical pesticides (Azadirachta indica extract), and judicious use of less potent chemical pesticides. Planting dates and seasons do not have an effect on pest population and diversity.