Influence of production system, shade level and altitude on coffee insect pests and blotch miner parasitoids at gera-gomma, ethiopia

Abstract

Coffee is one of the most traded commodities worldwide, and it is an important export crop and millions of the people generate their livelihood. The crop suffers from many biotic and abiotic constraints resulting in low average national yield in Ethiopia. Insect pests are one of the factors responsible for low national yield. The objective of the present study was to determine the influence of production system, shade and altitude on leaf damaging, berry feeding, sucking insects and some gastropods and on blotch miner parasitoids in different coffee production systems. A total of 60 plots were assessed in wet and dry seasons of 2018/2019; under four coffee production systems, along different altitudes (1506 –2159) and shade canopy closure (13-83%). For the leaf damaging insect pests two branches were randomly selected from each of the 16 trees per plot and the total number of leaves and damaged leaves was counted. The same 16 trees were examined for presence/absence of the other coffee insect pests and gastropods. The relationship between parasitoids and predictor variables was determined. Production systems showed a significant effect on leaf damaging insects and increased with intensification. The percent infestation of coffee leaf skeletonizer (Leucoplema dohertyi) ranged from 4-84 and 18-60 during wet and dry season, respectively and no coffee trees were free from this pest during assessment. This insect was the most commonly and frequently detected among other leaf damaging insect pests. Shade canopy cover was negatively associated with coffee blotch miner (Leucoptera caffeina) and serpentine miner (Cryphiomystis aletreuta) in 2018/2019, respectively. As altitude increased the leaf damaging pests decreased. The highest (51.69%) and lowest (6.40%) parasitoids emerged from sample collected under semi forest and plantation coffee, respectively from the total population, while higher blotch miner adult moth was found in plantation coffee at low altitude. Parasitized larvae and emerged number of eulophids increased with altitude. Intensively managed coffee production systems significantly increased the abundance of slug and coffee insects. Among previously reported minor insects, coffee berry moth (Prophantis smaragdina) was the most commonly and frequently detected insect with mean proportion of 49.00and 34.84% in plantation and semi plantation coffee, respectively during wet season. Besides, coffee berry borer (Hypothenemus hampei) was again the most frequently detected pest on left over berries with average infestation of 27.80 and 52.88% during wet and dry season, respectively under plantation systems. Among berry feeding, scales insects and snails; Antestia bugs (Antestiopsis spp), berry moth, berry borer, halmet scale (Saisettia coffeae) and medium snails were negatively and coffee green scale (Coccus alpinus) and mussel scale (Lepidosaphes beckii) was positively associated with shade intensities. Most of coffee insect pests, slug and snails decreased as an altitudinal gradients increased except mealybugs, green and mussel scale which were positively related with altitude. This may implying the effect of shade and altitude variation depending on coffee insect species. Maintaining shade levels between 30-50% can be used as cultural insect pest’s management options, but it depends on altitude, insect species, shade types and season. In combination with other management options, parasitoids can help to reduce pest damage due to coffee blotch miner. Identification of parasitoids is recommended for further study.