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Professional area | Diseases factsheet | Pests | Duponchelia

Pests

Duponchelia

This moth can cause damage to a wide range of potted plants, among which the cyclamen.
Be careful: once the pest is well present, it is too late to react!
In its natural environment, the Duponchelia is active from April till October. In France it propagates at the end of spring/ beginning of summer and grows during the summer.
At the beginning, the larva is quite small “like a sciaria” and reaches 2 to 3 cm at its final stage. The adult moths are small with a long abdomen curved upwards.
On young cultures, the larvae attack the region just above the hardly developed bulb and eat it.
Most of the time, the plant manages to produce leaves and therefore it becomes more difficult to discover the larvae. If preventive measures have failed, or if interventions have come too late, one can try to control the larvae.  
How to cure? In fact the efficiency of the actions depends on the right moment. Bacillus thuringiensis Kurstaki, Steinernema carpocapsae, Hypoaspis, lamps or traps, homologated products, etc. 

> Highly difficult to control

This moth can cause damage to a wide range of potted plants, among which the cyclamen.
Be careful: once the pest is well present, it is too late to react!
In its natural environment, the Duponchelia is active from April till October. In France it propagates at the end of spring/ beginning of summer and grows during the summer.
At the beginning, the larva is quite small “like a sciaria” and reaches 2 to 3 cm at its final stage. The adult moths are small with a long abdomen curved upwards.
On young cultures, the larvae attack the region just above the hardly developed bulb and eat it.
Most of the time, the plant manages to produce leaves and therefore it becomes more difficult to discover the larvae. If preventive measures have failed, or if interventions have come too late, one can try to control the larvae.  
How to cure? In fact the efficiency of the actions depends on the right moment. Bacillus thuringiensis Kurstaki, Steinernema carpocapsae, Hypoaspis, lamps or traps, homologated products, etc.

 

 

          

Excreta and silk threads together with a Duponchelia caterpillar in the heart of a cyclamen

> On the upsurge this year

This insect is, in fact, not a new pest. It has been spreading across Europe since 1984 : Finland, then Italy, Germany, the Netherlands (1989) and then in France since 1998 : the Anjou area, followed by Aquitaine (2000, 2005), Poitou-Charentes (2004, 2005), Rhône-Alpes, Languedoc, Brittany (2005)… A movement spreading from the north and, recently, it would seem, also from Southern Europe.
It appears to be progressing rapidly this year, in particular in the South-East and the West. We have already been informed of cases in Germany, and Italy. Three cases have been also detected in Ontario (Canada).
Technicians, plant breeders, plant suppliers and producers have all responded promptly to our appeal for help, thus enabling us to review the knowledge acquired by industry players, and share common experience and tips in order to find solutions, and above all avoid wasting too much time.

> Recognizing the pest

Duponchelia is present in its natural habitat from April to October. In France, it disperses at the end of spring/beginning of summer and develops in summertime.
It is capable of spending the whole year in greenhouses (chrysalis hibernation).
Duponchelia is very much at home in moist places and cultivated areas. It can lie in wait in crop debris (moist deadwood, discarded plants, tips).

Eggs

Ranging from pink to red in colour (sometimes greenish-white at the outset), isolated or arranged in small groups (piled up), they are usually found on the inside (near the veins) or outside of leaves, but also on stem bases, or again close to the soil line. Observing them is possible albeit very difficult. According to our sources, they measure between 0.5/0.7 mm or 2 to 3 mm.
A female can lay up to 200 eggs (in its short lifetime), the latter having an incubation period of between seven and ten days.

 

           

Duponchelia caterpillar

 

The larva

At the outset, the larva is very small [like a gnat], according to some producers, however it can reach from 2 to 3 cm in the final stage. Long and shiny, it is creamy/brown coloured, with a dark head and brown “shields” aligned on its abdomen. It has four pairs of “false legs”. It is a webworm whose mandibles are suited to digging out tunnels.
The larvae are very mobile with some observers even saying that they “run”. In fact, they seem disturbed by the light as soon as the leaves are lifted up.
They live on many different parts of the plant, above all on the crown, but also in the roots or under the young leaves, and in the top layers of leaf mould. They can also be found under pots, in organic waste…
The larvae can be found between the petals in the Gerbera cultures.
N.B. : the Duponchelia larvae can be confused with those of other species during the caterpillar stage.
The larva develops over a four-week greenhouse period; the pupation (chrysalis) period then lasts one to two weeks, or more under winter hibernation conditions.

The moths

 

            

 

The adults are also small but have some special characteristics : grey/light brown (9 to 12 mm long), with a long abdomen upturned at the tip when in flight (this criteria is particularly helpful for diagnostic purposes). They live for one or two weeks.
A wavy white line runs across the forewings.
It takes six to eight weeks for the transition from egg to adult and nine generations can follow each other at 22°C (71°F)…
The moth mainly flies at night, however, unlike other moths, Duponchelia can also see during daytime : it flies if it is disturbed (low-flying, just above or in the crops).
They fly very quickly, with some observers actually referring to “squadrons” of Duponchelia moths when they arrive in numbers.
In Belgium, these moths are graded as "true migrants" ; they are sometimes described as “good long-flight” insects in their natural habitat, hence the risk of geographical dispersal.

> How can they be detected in time ?

In fact, all of the professionals contacted confirm that when the Duponchelia is detected it is unfortunately too late : when the symptoms are patently obvious, the pest is already well and truly bedded in, and the resulting damage is virtually beyond repair.
In order to track it down in time, it is essential to be aware of its development cycle, biological phases, and way of life, as well as knowing where to locate it.

At the young plant stage

On young crops, the larvae attack the top of the recently developed bulb (crown) they are boring into. Once rendered defenceless, the bulb is unable to recover, and cannot grow new leaves or flowers.

During cultivation

More often than not, the plant manages to produce its foliage : nothing can be discerned, but it may be that the damage has already been done. Explanation: the larvae nest in the middle of the plant, feeding joyfully on the tender buds growing there (right to the very last one), as soon as they are formed, while they are still not out of the foliage process. They also bore into the leafstalks.
The producer will belatedly notice the areas which are late flowering, or examples of low production, or even a lack of production in serious cases.
Other damage may be experienced, depending on the host vegetable species : tunnels in the root system and in the leafstalks or stems, bites in the leaves or flours (in a similar manner to slugs, but without the slime), perforations and presence of faeces (in the Begonia et Poinsettia lower stems and flower stalks), buds failing to appear…
Repeated intervening action undertaken early enough may sometimes save plants. If the larvae are destroyed just in time, it will be possible to see the bulb begin to produce buds again on the fringe of the areas have been bored, providing hope of subsequent reflowering…

At the advanced stage

At the final stage, if care has not been taken in time and therefore the problem not been treated, “nests” (faeces and silk thread bound together) will be observed. In some cases where these are noticed belatedly, the whole plant may suffer from sagging (care must be taken to avoid confusing this with cryptogamic diseases. The stems are not black and there are no signs of rotting).
The quantities of larvae may, at this late stage, be very consequential (a case of some 120 larvae/m2 was observed two years ago).

> What can be done to prevent such problems?

What should be done to avoid being faced by a fait accompli, an almost impossible situation? The information to hand is sometimes contradictory (degree of effectiveness of blue lights, and certain auxiliaries or products). However, the various accounts gathered together enable recommendations and tips to be shared (cf.  "The key word: Prevention” inset…).

Clues left by the caterpillars

Track crops thoroughly and search through the heart of the plants thus enabling action to be taken as soon as the first areas of the outbreak are located.
The larva burrows into the soil, but leaves clues on the plant : faeces, and sometimes rolled up leaves.
Locate the “cocoons” in particular : oval, 15 to 19 mm long, solid, arranged under the leaves, on the surface of the pot, or in the first few centimetres of the mould. These are signs indicating the pupation stage. However, their composition (organic waste, excrement) makes it difficult to detect them because they are earth colour.
The chrysalides are surrounded by or intermingled in a clearly visible silky white envelope/web/cocoon which protects them.

Tracking the moths

Monitoring the flight of the moths is very important (in particular at nightfall when they are very active). Solutions suggested by producers who have already been affected:

  •  "blue lights" help to track them down (not to be used in open greenhouses to avoid attracting moths from outside) and may enable risks to be assessed. However, they do not enable the groups already present to be controlled or eradicated;
  • at the time when the first moths come out from their hiding places at winter’s end, crush the chrysalides using your hands : some producers, caught out a first time, hunt down the first moths as soon as winter ends, in order to try to detect the first adults emerging from the chrysalides as soon as possible, knowing that that they are often hidden in dark webs, or in the plastic bubble insulation …  
  • another example: in managed chrysanthemum and Kalanchoe cultivation, the moths often hide during daytime in darkening black webs.

N.B.: Hormone traps are not effective (the sexual pheromones are particular lepidoptera species ; not all of them have been isolated and synthesized) and the yellow traps might attract the moths…

What should be done when the damage is visible?

… or when it is essential to anticipate the risk of damage for the year following the diagnosis…
The choice of the method used to fight this menace depends, in fact, on the seriousness of the situation at the time T.
Most of the time, for those lacking experience in this field, Duponchelia is observed when serious damage has been caused : it is already almost too late and it will be essential to be far more watchful the following year.
If the fight to prevent the pest from wreaking havoc has failed, and if the diagnosis is conducted too late, it is therefore necessary to try to intervene at the larva stage.
The difficulties are all the greater since a diagnosis often conducted belatedly leads to the simultaneous presence of several generations, and therefore large populations.
Destroying affected plants which are beyond help prevents the disease from spreading to the test of the cultivation or the greenhouse. It is necessary to put the plants in a plastic bag and burn the waste provided that the quantities of plants affected enable you to do so. Theoretically, there is no risk of the pest entering the household waste network.
However, never throw the plants on a tip, let alone a compost heap, otherwise the heat will favour the spread of moths, encourage greater numbers the following year and the dispersal of moths to neighbouring crops.
It goes without saying that plants affected by this pest should not be sold until it is certain that the pest has been completely eradicated.

Just at the right time

What corrective action can be taken ? In fact, very often the efficiency of the action depends on intervening at the right time…
Once again, it is far better to anticipate when receiving orders.
If diagnosis has been delayed, and the preventive action taken has failed, efforts must again be focused on the young larva stage.
N.B. : its cleverly hidden cycle in the middle of the plant make it a difficult pest to track down.

Bacillus would be the most effective

Even though some sources sometimes describe it as being ineffective, the producers concerned by the problem highly recommend the Bacillus thuringiensis Kurstaki bacteria for young larvae. Repeatedly spray every week as long as the risk of laying persists.
A German publication has announced relatively positive results having been observed with Steinernema carpocapsae and Trichogramma spp (77 % efficacy).
Several avenues can be explored to limit the development of populations, in particular with Hypoaspis miles (a polyphagous predatory mite, living in the ground, which is thought to act on the Duponchelia eggs and young larvae) and Heterorhabditis megidis (nematode which preys on otiorrhynchus larvae).

Lack of approved products

The crucial problem of the reduced range of authorized pharmaceutical products once again raises its head. The authorized products which can be used against noctuid moths can prove effective.
Evening spraying, possible involving the use of a spreader, should be planned ensuring that the pulp reaches the heart of the plants. Choose compatible products (however, often only acting on contact), if working in an IPM context.
Or give preference to applications during watering, and soil treatment and preferably systemic (if working in an IPM context).
Allow for at least three treatments five days apart.

Alternating product families

In the event of a serious situation, the best solution would probably be to alternate chemical solutions with the Bacillus bacteria in order to fight against the different development stages of several generations living side by side and thus achieve “acceptable” tolerance thresholds.

> Using lights or not?

According to the majority of the professionals contacted, it is virtually impossible to fight against the pest in a curative manner at the adult stage, in other words against moths.
Some of them have tried using “blue lights” of the “blocking type”, with varying degrees of success and it is fair to say that no consensus has emerged concerning this approach.
In fact, although they are useful for detecting the first adults, they do not enable a significantly-sized population to be eradicated. Care should also be taken with regard to their potential attractiveness for the useful auxiliaries if working under IPM conditions…
Advice from a professional: there is no point in putting the lights above the crops.
Firstly, the moths do not fly high enough to get trapped in this way.

Furthermore, it is recommended to avoid putting them above the crops, but instead place them above paths. A plant supplier gives the following advice:

- It would seem that the young moths, recently hatched, are not attracted by the blue lights. The adult moths are more liable to get trapped at the pre-laying stage. When the insects get burnt or electrocuted in the light, they explode. The eggs are then spread over a wide area below the light. If they fall on the crops, they hatch as larvae and infect the cultivated area to an even greater extent. If they fall on the paths, they hatch without causing damage.


Sylvie Lemmet Burlat (technical support representative at Gie Fleurs&Plantes du Sud-Ouest) has observed:

- We have been testing these lights for three years with two partner companies (one for a “geranium-related” Cacyreus issue, the other for the cyclamen-related problems posed to cyclamen by Duponchelia). It is difficult to locate the harmful species among all of the captured moths, even by limiting their use when the openings are closed : this cannot be used either as a means of fighting against this pest or a means of detection …



Caution

This advice sheet is based on the methods used at the SCEA at Montourey (Fréjus, France). These procedures may need some modification to adapt them to other climatic situations. Before starting to grow cyclamen there needs to be a review of precautions against pests and diseases.   We must point out that our advice and suggestions are offered for information purposes and therefore cannot include any guarantee of specific results; it is a good idea to carry out trials beforehand.

 

Pests :

S.A.S Morel Diffusion

2565, rue de Montourey
83600 Fréjus - France

International telephone : +33 (0)4 94 19 73 04
Switchboard : + 33 (0)4 94 19 73 00
Fax : +33 (0)4 94 19 73 19

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