EFFECT OF TEMPERATURE AND REARING METHOD ON DEVELOPMENT AND FECUNDITYOF TETRANYCHUS-URTICAE (ACARINA, TETRANYCHIDAE)

The effect of temperature on the development and fecundity of the spid er mite, Tetranychus urticae (Acarina, Tetranychidae) has been studied applying three mite-rearing methods: A - the live leaf culture method , B - the leaf disk method. and C - the detached leaf culture method. Bean plants were used as food source. The study was conducted using al l combinations of the three rearing methods and three temperatures (20 , 25 and 30 degrees C). Both temperature and rearing methods were foun d to be key elements influencing the life history of T. urticae. The d uration of the quiescent and active stages and the life history compon ents, i.e. net reproductive rate (R(o)), intrinsic rate of natural inc rease (r(m)), generation time (G) and doubling time of the population, were investigated. In all rearing methods rising temperature caused a shortening of the adult lifespan. Using method A the fecundity of mit e females decreased with increasing temperature. Fecundity was high us ing each combination of 30 and 20 degrees C with rearing method B and C. However, the application of these methods at 25 degrees C reduced m ite fecundity. Out of ail the experiments, the highest number of eggs laid by a female per day (16.4) was observed in method C at 30 degrees C. Prolonged development of all stages was observed at all three inve stigated temperatures in method B. Neither temperature nor the rearing method influenced significantly the sex ratio of the spider mite prog eny. On average, 86.2% of the spider mite eggs developed to adult stag e in all rearing methods except method C at 30 degrees C, where less t han 66.2% of the eggs reached adult stage. With rising temperatures in all rearing methods, the r(m) increased and the G as well as the doub ling time of the population decreased.