Relative Abundance Of Mirids Of Cocoa In Differently Managed Systems In The Eastern Region Of Ghana

ABSTRACT The temporal distribution of four important cocoa mirid species (Distantiella theobroma Dist, Sahlbergella singularis Hagl, Helopeltis bergothii and Bryocoropsis laticollis) was studied in three differently managed cocoa farming systems from May 2013 to April 2014. In addition, the incidence of Bathycoelia thalassina, Characoma stictigrapta, Anomis leona, Earias biplaga, Eulophonotus myrmeleon, Oecophylla longinoda and Crematogaster africana, were recorded. The three systems were: Organically managed cocoa farms located at Akwadum, Experimental farms at CRIG, Tafo and Farmer‟s farms also at Tafo. Each system was replicated three times each of size one acre with an average of five hundred (500) cocoa trees. Sampling was done monthly on one hundred (100) randomly selected tagged cocoa trees per farm. Parameters which were assessed over the period included: population counts of mirids, incidence of other insect pests and natural enemies as well as climatic data on Rainfall, Temperature and Relative humidity. Records of insects were made from visual counting from the base of the cocoa tree to hand height (2 m) of each of the tagged trees. The owners of the farms were also interviewed on the type of farming systems they operate, knowledge on good agricultural practices and pesticides use pattern. The Organic and the Farmer‟s farms recorded the highest mirid numbers in September with peak populations of ninety nine (99) and fifty eight (58) respectively per three hundred (300) cocoa trees. The Experimental farms recorded the lowest mirid population of fifty (50) per three hundred (300) cocoa trees with the peak population occurring in March. Both the organic and Farmer‟s farms showed a similar trend in the distribution of mirids with the highest peak occurring in September. In addition the incidence of Bathycoelia populations found in the Farmer‟s  farms, Experimental farms and the Organic farms were twenty eight (28), seventeen (17) and six (6) respectively per three hundred (300) cocoa trees. Two seasonal peaks of Bathycoelia were observed in all the three farming systems with the highest peak occurring between May and August and the second between January and April. The number of pods damaged by Bathycoelia was high even at low pest densities. The organic and the Farmer‟s farms recorded the highest of 50 and 45 pod damage per 300 cocoa trees in September with the Experimental farms recording 11 in October which was the highest over the period. There were 57, 55 and 29 individuals of Characoma per 300 cocoa trees in the Organic, Farmer‟s and Experimental farms respectively. The number of Cocoa trees with mealybugs out of 300 trees per plot were 123, 94 and 29 for Organic, Farmer‟s and Experimental farms, respectively. There was a negative correlation between natural enemy population and pest incidence. Peak relative humidity data of 86.7% and 83.8% were recorded in July and August and the lowest temperature of 28.5C was also recorded in the same months favouring the multiplication of mirid numbers.