Species Composition And Host Association Of Thrips (Thysanoptera) In The Eastern And Greater Accra Regions, Ghana

Abstract

Thrips are crop pests causing damage to a wide range of crops ranging from fruits to vegetables to ornamentals through direct feeding or oviposition on plants. The main objective of this study was to determine the species composition of thrips and their host range in some selected parts of Greater Accra and Eastern Regions of Ghana. Thrips were collected from flowers, leaves and twigs of vegetable, ornamental and tree crops by beating and jarring and identified to species level. Fifty sticky traps comprising 25 each of Blue and Yellow traps were also set in vegetable farms for 7 months, September 2014 to March 2015 to trap thrips species. Data on average daily temperature and rainfall were collected from the Ghana Meteorological Agency located at Mempasem in the Greater Accra Regionand used to establish their relationship with trap catches. Farmers’ knowledge of thrips and their pest management practices was assessed using a survey questionnaire. Abundance of thrips was studied on vegetable crops and within plant distribution of Thrips palmi determined on cucumber plants. Over twenty species of thrips were recorded. Major thrips species recorded include; T. palmi, Megalurothrips sjostedti, Frankliniella schultzei and Thrips tabaci. In all, 13367 adult thrips were captured by traps. Individual trap types were 8206 (61.4%) and 5161 (38.6%) by the Blue and Yellow traps, respectively. Generally, there was no significant difference (P =0.363, DF = 1, P>0.05 = α) among trap catches. Both rainfall (R2 = 0.0142, P = 0.530, P > 0.05 = α) and temperature (R2 = 0.0603, P = 0.191, P > 0.05 = α) were not significantly correlated to trap catches. However, the number of thrips in sticky traps from one locality (East Legon) was significantly positively correlated (R2 = 0.1346, P = 0.0461, P <0.05 = α) with average weekly temperature. Only 29% of the farmers interviewed knew thrips and had experienced thrips on their crops. Survey results showed a 100% reliance on chemical pest control by farmers with most of them dependent on personal experience for agronomic practices. Mean number of thrips was significantly higher (Fpr =0.012, DF = 12, P < 0.05 = α, LSD = 1.15) on eggplant and cucumber compared to other vegetables examined. Four plant species including eggplant, cucumber, gboma and sweet pepper were examined for thrips abundance recorded T. palmi infestation. Even though there was no significant difference (Fpr = 0.6292, P > 0.05) among thrips counts from various plant species, more adult T. palmi were recorded on cucumber leaves. For within plant distribution, there was a significant (Fpr = 0.0036, P < 0.05) difference among mean numbers of thrips on young, middle and bottom leaves, with counts from young (mean = 16.1) and middle (mean = 10.1) leaves significantly higher (q = 5.337 > q-critical =3.532, α = 0.05) compared to the bottom (mean =3.2) leaves. In conclusion, several species of thrips infest vegetable and ornamental plants in Southern Ghana and are polyphagous insects, infesting a wide range of plants species. Thrips palmi was recorded in Ghana for the first time. Knowledge of thrips was very limited among crop growers. The improvised sticky traps were effective in capturing thrips, thus may be good for monitoring early and small thrips populations in the field.