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.