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HOME En - Fr - Es - De English The Fight against the chestnut gall wasp (Dryocosmus kuriphilus), scourge of chestnut trees in Italy

The Fight against the chestnut gall wasp (Dryocosmus kuriphilus), scourge of chestnut trees in Italy

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13, June 2011 francese_18x12 spagnola_18x12 italiana_18x12

castagno_danni_cinipideThe "Chinese wasp”, is a parasite" imported " from abroad, threatening the great wealth of chestnut trees of “Belpaese”, more than 780,000 hectares the 7.5% of the national woodlands. The production of chestnut honey is therefore likely to be resized. Moreover eucalyptus trees too are  attacked by a new parasite, the psylla, with effects even more disastrous and deadly for these plants. What can we do? What can beekeepers do for the defense of these important and essential botanical resources to continue producing  special and appreciated products like honey and pollen secreted by the flowers of these trees?


The chestnut tree characterized the landscape and production in Italy
Italy is the third largest producer of chestnuts of the world and is one of the few countries that started the gradual and more significant valorization of chestnuts amber honey  with the particular bitter taste. In our country we produce thousands of tons of chestnuts high quality honey and from 50 to 70 million kilos of chestnuts: 46% in Campania (especially in Avellino province), 18% in Calabria, 16% in Lazio 7.7% in Tuscany and 5% in Piedmont.


castagno_vivaioHow did the plague arrive?
The introduction of the parasite started at the beginning of the 2000, thanks  to the import of chestnuts species  in Italian nurseries from unknowns places. These cultivar were boasted for the rapid growth of the chestnuts and greater size;  twice  time more than our chestnuts, but  tasteless. The lure of achieving a better price – If you use less chestnuts  to get to a kilos you have more profit- helped to spread this dreaded parasite. In subsequent years, the gall wasp, partly due to the underestimation of the phenomenon has spread throughout Italy and has haunted all of Western Europe and before was observed also in  Japan,  United States, Canada and other regions.


Chemical fight against the gall wasp: bankruptcy!

A hand with gloves holding a bottle with poison simbol onTo combat the gall wasp the use of chemical substance is dangerous, useless, expensive and without positive effects: it is difficult and probably impossible to reach the outside part of the tree crown with pesticides (especially at the top and closest to the ground). The wasp can be affected by a chemical substance only when it’s outside the gall, for a few days when, without eating, it lays hundreds of eggs. However it’s documented (with yellow sticky traps) as, in the same place, the wasp flicker in different years, in different periods (depending on the weather) and not in a synchronous way but in a long arc of time. The number of wasps that survive the chemical treatments  however is more than sufficient to ensure the presence of the parasite in the area. Repeated experience with chemical treatment during all of the days of flickering, in Lazio and Campania, failed to eradicate the chestnut gall wasp from young and low trees in plain areas.

In contrast, the chemical approach should destroy:

1) native species that may already fight the wasp;
2) native species that have the potential to fight the gall wasp (but, given the recent arrival of gall wasp still have to "select" individuals, for example, more suitable to lay their eggs in the galls of the chestnut parasite);
3) local species fighting that other pests of chestnut (Cydia splendana, Curculio elephas) An unlikely containment of the gall wasp would be accompanied by a higher percentage of worm-eaten chestnut thanks to the destruction with chemical treatment of a species that limits the number of weevil.

A danger signal with a cross on, saying toxic hazardThe only prospect for re-establishing a balance: biological pest control
The use, of banned pesticides, as well as not having effect against the Oriental wasp, damages the environment, pollutes the ground and water and kills the native antagonists of the Dryocosmus kuriphilus.
The strategy adopted to contain, within acceptable limits, the wasp was initiated by Professor Alberto Alma, from Turin University, head of biological control in Piedmont.
Both the Ministry of Agriculture and the Regions have realized, with a specific plan for chestnut developed in three-year, that biological pest control has no alternative because it has already proved effective and combines both the defense of the chestnut and the preservation of environment.


Picture of torymus auratus sinensisThe biological pest control strategy provides the reproduction and the "launch" of the most effective antagonist of the Dryocosmus kuriphilus; the Torymus, a Hymenoptera too who is also from China. The Torymus colonizes the territories in which it is inserted with a relatively slow biological time: about 1.5 square kilometers every year. Now each region will produce a quantity of Torymus enough to counter the Chinese wasp. Obviously, the chestnut trees react positively when the amount of Dryocosmus kuriphilus  decrease. The destruction of the larvae gall made ​​by both native Torymus (that usually control the pest of oaks) and  the antagonism introduced and naturalized (Torymus sinensis), will lead to a reduction of the number of individuals of that gall wasp and the negative effectsobserved on the chestnut tree will be almost insignificant.

A balance perspective that needs  years, at least 10 if not more, to achieve substantial results. In fact, the reproduction and the launch of the antagonist requir investment and work for several years. However, it’s true that in some areas of Piedmont, the biological pest control has already managed to reduce the infestation and restore an ecological balance in favor of the plants.
It’s desirable that a similar fight strategy must be activated and implemented as soon as possible, even for the parasites from bioinvasione as the Psylla that is laying on the line the survival of eucalyptus trees in our country.

What can beekeepers do?
Beekeepers that operate in most areas of chestnut can and should:

notebook with pencil on1. Start to known this pest of chestnut.
2. Report to the competent authorities the presence of the parasite.
3. Urge local authorities to ensure that adequate investments are made ​​for timely and adequate funding and operation of stations playing the predator.
4. Ask for and collaborate, with the authorities for the proposed launch of providential Torymus pairs, with the knowledge that, with the gall wasp, very probably need to live together, as happened in China and Japan, as happened in Italy with the blight: devastating disease, destructive, just arrived from the pathogen, but for years no longer as dangerous then.

Francesco Panella


logo del mipaaf

June 24, Technical Meeting of Mipaaf for chestnut culture, allocated one million Euros. Shared information on measures and economic cooperation with the local institutions.

Was held on Friday 24, in the room 'Cavour' inside the Ministry of Agriculture, Food and Forestry, the meeting about the 'chain table nuts - chestnuts section', which was attended by the representatives of the Ministry, the representatives of the regions, government and provincial and municipal associations.
At the meeting were presented and discussed the guidelines of the ministry to intervene against the emergency caused by the chestnut gall wasp.

It was announced the allocation, immediately available, the sum of one million Euros to take action that will be developed along four lines, with priority given to the first two points:

• The establishment of breeding areas of Torymus sinensis, the natural antagonist of Drycosmus kuriphilus (the gall wasp of chestnut). Regions will submit projects about the location of these areas and the Ministry will finance them;
• The strengthening of the multiplication center Divapra of Turin University. The Multiplication is managed by Professor Alberto Alma, who was the first to breed Torymus;
Assessment guidelines about the research including relating to adaptation at the territory of the antagonist, the incidence of gall wasp on the chestnuts production and the possible 'hybridisation' of Torymus sinensis with indigenous species;
• Better connections with the Inea (National Institute of Agricultural Economics) and with the associations in the area, which will provide data on the presence of chestnut trees, follow the procedures for intervention at local level and inform the operators on what to do.

Participants reiterated to the representatives of the Ministry the urgency of an immediate availability of resources to face the emergency, and also asked for an involvement of all the regions affected. It was confirmed by the Ministry the intention, in addition to already available resources, to allocate more funding to tackle the emergency, and the need to launch greater cooperation with local institutions.
Source: Mipaaf

Translated by Michele Valleri