| dc.description.abstract | The influence of selected relative humidity regimes on the development and growth of
of the various immature stages from egg to adult of the predacious mite,
Typhlodromalus aripo De Leon, was studied in the laboratory at a constant
temperature of 27 ± 2 0 C. A related greenhouse study where the temperatures and
relative humidity fluctuated closely paralleling the outdoor conditions in Eastern
Kenya Province was also carried out. T. aripo was raised on its natural diet of
phytophagous cassava green mite, Mononychellus tanajoa Bondar, reared on cassava
apices of young stems. Development was measured as the life history of the mite, that
is, the total duration of development from egg to egg; whereas growth was determined
as the duration in days it took each immature stage to change into the next stage. A
coefficient of correlation between the mite developmental period or life cycle duration
and relative humidity showed that there was a negative relationship between
decreasing relative humidity and the length of development or duration of the mite's
life history. In other words, a decrease in the relative humidity increased the duration
length of the life history which also resulted in increased mortalities. Similarly, there
was a negative relationship between the fecundity or number of offspring (eggs)
produced by individual female mites with respect to lower relative humidity regimes.
In this case, the growth period of individual young stages was not affected by either
low or high relative humidity levels. The tendency by T. aripo motile cohorts to
aggregate at the fresh cassava apices than at the older or wilting ones was an
indication that they were attracted to areas of high relative humidity regimes usually
caused by transpiration . These findings on the relationship between relative humidity
regimes and durations of the life cycle stages and growth rates of the various
immature stages of mite allows a better understanding of its population dynamics. In a
similar experiment the current study has confirmed these findings. The knowledge
gained will contribute to mass rearing methods of this predacious mite in greenhouse
for further release in cassava fields for biological control of cassava green mite pest. | en |
