Tunisia - Iresa

Table 2. Frequency of the chemical treatments
in citrus orchards (Cap-Bon and Bizerte
regions, Tunisia) made from 25 March to 29
April 2010
Chemical treatments Scarred fruits
(number / year)
4 - 7
9 - 14
16 - 21
25 – 30
(%)
46.37
57.26
60.26
65.52
DISCUSSION
This work on citrus thrips in
Tunisia has lead to two results: a
preliminary composition of the species
living on citrus trees and a global
estimation of the proportion of fruits
damaged either by thrips or other factors
causing nearly the same symptoms.
The inventory of thrips in 7 citrus
orchards, in which the proportion of
scarred fruits were high, showed a varied
fauna composed by 10 genus and 13
species, 12 of them are plant feedings and
one is predator. As compared to findings
from other countries, the biodiversity of
thrips species in citrus orchards is lower.
Indeed, often more than 40 thrips species
have been identified in association with
citrus in the world (13). In Florida, for
example, the inventory of thrips species
in 7 citrus orchards showed 36 species
among which 7 are predatory, 21 are
phytophagous and 8 are mycophagous
(8). Our results expressing a relatively
low biodiversity can be explained by the
high number of chemical treatments
applied in the sampled orchards (in
average 16 treatments/year). The forty
species found in Florida were from
orchards with reduced to no pesticide
spray programs. Moreover, the short
period of the sampling (from 25 March to
29 April 2010) could explain the low
number of collected thrips species. For
instance, in Florida, the 36 species
identified were found after a sampling
monthly for thrips over 13 months in 7
citrus orchards (8). Furthermore, in our
work, thrips were collected mainly from
citrus trees, while the cover ground plants
on which can live most citrus thrips
species, have not been regularly sampled.
Among the thrips species
identified, P. kellyanus, the most
economically important species, was
found to be the less frequent as it was
noted only in the region of Bizerte in one
orchard on three in the locality
of Azib on Meski oranges.
The other few widespread species
that have been reported only in Cap-Bon
and in one or two on four orchards are: A.
citricinctus, T. major, T. tabaci, T.
angusticeps and S. graminum. All these
species were found only on Valencia late
oranges.
The onion thrips, T. tabaci have
a broad host range including citrus genus
but is not reported as a typical pest
of citrus (26). The species T. major is
also polyphagous but has been
reported only once as a damaging pest
of citrus in North Africa (6). The species
T. angusticeps, rather associated with
cereals and leguminous crops, has been
reported also on citrus in Turkey and
Spain but its status as pest of citrus has
not been confirmed yet (26). The thrips
S. graminum which is normally
associated with grasses (12) was also
found on citrus but is not reported as a
pest of this crop (20). The thrips
Aeolothrips which colonizes herbaceous
plants, shrubs and trees in countries
of Europe and North Africa appears to be
a facultative predator (12).
The most widespread species
found in both regions of Cap-Bon and
Tunisian Journal of Plant Protection 48 Vol. 7, No. 1, 2012