Pear psyllid complex (Psylloidea) of Georgia, with characterizing interspecific competition between Cacopsylla pyri (L.) and C. bidens (Sulc), comparatively new pest species for Georgia’s horticulture

Author: Arnold Gegechkori
Keywords: Horticulture, Psylloidea, interspecific competition.
Annotation:

• Psyllids are an important group of phytophagous insects including a rather large number of pest species of economic significance (Hodkinson, 1974; Loginova, 1972; Gegechkori, 1984, 1996; Burckhardt, 1994). Instead of nine species known earlier in the Caucasus (Loginova, 1972), 17 locally or largely economically important pest species were found in this region during our studies in 1963-1990 (Gegechkori, 1996). • Among five species trophically linked with pears in horticulture, the most serious pest is C. pyri. Cacopsylla pyricola locally (in the mountainous areas), C. pyrisuga sporadically can be harmful. In southern part of South Caucasus, the economically most important species is C. bidens. It must be emphasized that at the boundary of two countries from southern part of the region (Armenia, Azerbaijan), located more close to subtropical organisms within upper latitudes (380-390 N), the invasion of thermophilous tropical and subtropical latitudes (400-450 N) of the Caucasus is noticeable. This is considerable in arid regions of Georgia (e. g., Hystrix indica, Panthera pardus). Among invertebrates recently entering into Georgia, C. bidens should be mentioned. This species was recorded in agrocoenoses in this country till 1990s (Gegechkori, 1990, 1996, 2000). • In arid natural habitats of East Georgia, two species - C. permixta and C. pyri - coexist on their host plants - xerophytes wild pears (Pyrus salicifolia, and other species of the same autoecology); in anthropogenic habitats in Kakheti and Kartli, two districts in East Georgia, another pairs - C. bidens and C. pyri - coexist (Macharashvili, 2002; Gegechkori, Ginturi, 2005). In natural conditions, the ratio between the two populations is 80% to 20% in favour of C. pyri, but in agrobiocoenoses this ratio is approximately 98% to 2% in favour of C. pyri. • Because C. bidens coexists with C. pyri, still less the both species are characterized by the same bioecology, therefore we are studying the ways of avoiding interspecific competition between these two psyllid species. This avoiding of competition is attracting by the sharing of the vegetational organs of the host plant, therefore to make the allopatric ranges on the same hosts (Gegechkori, Macharashvili, 2002). This problem has as theoretical and also an applied interest.