Influence of weather and soil factors on the incidence and severity of damage by cassava green mite and performance of a released phytoseiid in Gomoa district of the Central Region of Ghana

Abstract

The main objective of the study was to investigate how weather and soil factors in Gomoa district of the Central Region of Ghana affected the incidence and severity of damage of the cassava green mite (CGM) and also the performance of a phytoseiid – a biocontrol agent against the green spider mite. The study was carried out on 10 cassava farms along a major from Accra to Cape Coast within the area where a phytoseiid, Typhlodromalus manihoti, had earlier been released. Data collected were on: incidence and severity of cassava green mite and phytoseiid; weather and soil physical and chemical properties. The paired comparison design was employed with the sprayed and unsprayed (presence or absence of phytoseiid) as treatments and sampling sites as replicates. Subplots measured 25 x 15 meters with a minimum of 250 cassava plants. The incidence, severity and population of the cassava green mite were observed to be highest in the dry season or short dry spell in the rainy (wet) season. Rainfall and severe drought acting indirectly on food availability to cassava plant were noted to be important mortality factors of the pest. Available phosphorus and organic matter were observed to hinder development and attack of the cassava green mite. However, soil nitrogen, available phosphorus and organic matter significantly promoted the development of phytoseiids. Temperature on the other hand had detrimental effect on the general development of phytoseiids.



JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 3, July (1999) pp. 11-30