Asiatic Palm Weevil [Rhynchophorus
A NEW PEST ON PALMS
In summer 2009, a true date palm (Phoenix
dactylifera) growing in a private garden in Portorož which the
owner raised from seed about 40 years ago, dried down. In
the official laboratory of the Agriculture and Forestry Institute Nova
Gorica a new species of harmful organism Rhynchophorus
ferrugineus (Olivier; Coleoptera: Dryophthoridae) was confirmed, in
respect of which the European Commission decision
2007/365/ES provides for emergency measures for the prevention of
introduction into the Community and its spread in the Community.
Thorough inspections revealed infested palm trees also ni Koper,
therefore we ask all owners of such plants to pay attention of the
symptoms of drying and holes in the crown of the palm. As a result, the
Phytosanitary Administration of the Republic of Slovenia issued on 4
September 2009 a decision on delimitation of the infested area.
Palm species threatened by Asiatic Palm Weevil
Rhynchophorus ferrugineus (Olivier)
Palms [Arecaceae (=Palmae)] are tropical or
subtropical or desert thermofilic plants, therefore in Slovenia they may
be grown only as ornamental plants in the areas with the expressive
sub-Mediterranean climate. The population of various palm species in
Slovenia is the most extensive in Istria and on Goriško. Within the
special control of Asiatic Palm Weevil in 2008, an inventory of
the palm species which grow in our country, and a rough estimation of
populations of individual palm species were made. According to this
estimation, the situation is the following:
The list of endangered species does not
Brahea armata (Slovene Istria, cultivated on the coast),
Butia capitata (rare) and European Fan Palm
Chamaerops humilis (Slovene Istria, Goriška).
In 2008, the phytosanitary inspection, in
cooperation with the Agriculture and Forestry Institute Nova Gorica,
inspected a number of palm trees on Primorska, however no signs of
attack were established. The inspection included the following:
99 palm trees of species Phoenix canariensis Chabaut
649 palm tress of species Trachycarpus fortunei (Hooker)
132 palm trees of species Washingtonia robusta Wendl.
79 palm trees of species Chamaerops humilis L.
The Asiatic Palm Weevil attacks various palm
species. Larvae drill into the upper part of the trunk, usually near the
apical meristem, and continue their way down the trunk.
This results in a complete desctruction of the trunk's core. The first
symptom is somewhat poor growth and wilting of new leaves, and finally
their falling down.
The top of the infested palm trees looks like being cut down or
suppressed. While the damage continues and the tissue is attacked
by various bacteria and fungi which also contribute to deterioration of
the trunk's core, also older leaves bent down, become yellow and die.
Such tree dies or even breaks at the most damaged spot. At the base of
leaves of infested trees, vegetable sap is usually dripping
from the damaged trunk, or excrement may be noticed which warns of the
possible attack of the Asiatic Palm Weevil. The entire development cycle
of the pest takes about 4 months. In one growing season, it usually
develops two generations. In the attacked plants we can
usually find larvae of different development stages, therefore also the
occurrence of beetles in the growing season is more or less continued
(except in winter).
If you notice any suspicious signs of
drying on the crowns of palm trees, please call an expert of the Agriculture
and Forestry Institute Nova Gorica (Slovene
Plant Protection Organisation).
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