Environmental And Cassava Variety Influence On Dynamics And Impacts Of Cassava Green Mite, Mononychellus Tanajoa (Bondar) (Acarina: Tetranychidae) In Tanzania

EXTENDED ABSTRACT

In Tanzania, cassava (Manihot esculenta Crantz) is an integral component of most cropping systems and is among the most important staples in many zones. It is an essential component as a food security crop and provides useful opportunities for extending labour use and sometimes considered as a famine reserve when cereals fail due to its drought tolerance. Cassava is attacked by several pests, among which cassava green mite, Mononychellus tanajoa (Acarina: Tetranychidae) is most important. Mononychellus tanajoa can cause a reduction of about 50% in leaf weight and up to 80% tuber yield loss. It is therefore a pest that can pose multidimensional problems that require multi–dimensional solutions. The current cassava productivity in Tanzania is near the lower end of internationally reported yields. Mononychellus sp. was first reported in Tanzania in 1972 at Ukerewe Island. At present cassava green mites have spread throughout the country and are prevalent in all the cassava growing zones of Tanzania. The current study aimed at establishing M. tanajoa pest status and distribution in the three major cassava growing zones. It also studied the damage inflicted on some commercial and local cassava varieties and examined the influence of the environment and seasons on the pest in Tanzania. Specifically the study aimed to i) determine the spatial distribution of M. tanajoa on commonly grown cassava varieties in the Eastern, Lake and Southern zones of Tanzania ii) evaluate the environmental influence on occurrence and perpetuation of M. tanajoa on selected cassava varieties and iii) assess the abundance and associated damage of M. tanajoa on commercial and popular cassava varieties in the Lake zone. The studies were conducted in the three major cassava producing zones (Lake, Eastern, and the Southern Zones) of Tanzania. The surveys were conducted in farmers’ fields during 2015 and 2016 dry seasons in the three Zones. A iii total of 5400 plants in 180 fields were assessed during 2015 and 2016 for M. tanajoa infestation and associated damages. Collected data were subjected to non-parametric analysis in SPSS and Kruskal-Wallis test was used to compare between the pest counts and distributions. Weather parameters were analyzed against the pest counts and associated damages. Results revealed that M. tanajoa counts were significantly (P