EFFECT OF CERTAIN ABIOTIC AND BIOTIC FACTORS ON POPULATION DYNAMICS
OF Retithrips syriacusMayet (THRIPIDAE:THYSANOPTERA) AND Panonychus ulmi KOCH
(TETRANYCHIDAE:PROSTIGMATA) INFESTING GRAPEVINE
S.H.Mannaa, F.A. Al-Zyoud* and A.M.M. Saleh
Bull.Fac, Agric.,Cairo Univ.,63:201-211(2012)
The black vine thrips, Retithrips syriacus Mayet (Thripidae: Thysanoptera) and the European red mite,
Panonychus ulmi Koch (Tetranychidae: Prostigmata) cause serious damage to grapevine. Biotic and
abiotic factors can be either helpful or harmful to pest’s population, and understanding of such factors
may contribute to better pest control. This study aimed at investigating the effect of the two predators
(Scolothrips longicornis and Amblyseius hutu), temperature and relative humidity (RH) on the population
fluctuations of these two pests on Muscat, Thompson seedling and Azmerly grapevine cultivars during
the 2007/2008 and 2008/2009 growing seasons. The results indicated that R. syriacus fluctuated
throughout the two seasons. The peak was recorded during June (2007/2008) and September (2008/2009)
on the three grapevine cultivars. Although, the population fluctuation of P. ulmi differed during the two
studied seasons, but the peak was recorded during May or June in both seasons according to the grapevine
cultivars. In both growing seasons, it seems that both pests have one generation a year, and high
temperature and moderate RH seem to be favorable for both pests. During both growing seasons, the
population of both predators reached a peak in May and June on the three cultivars. Minimum
temperature and RH played an important role in regulating the population changes of R. syriacus and P.
ulmi, respectively. Mean numbers of the two associated predators, Scolothrips longicornis and
Amblyseius hutu were significantly higher in 2007/2008 than 2008/2009 on Muscat and Thompson
seedling. There was a negative significant correlation between the populations of both predators and R.
syriacus and P. ulmi. In conclusion, the selected abiotic and biotic factors played the most important role
in regulating the population density of these two pests.