Selection of F1 Hybrid cyclamen

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These moths, just like the Noctuids, cause damage to cyclamen at the caterpillar stage (green caterpillars) especially on young and adult leaves.

As a rule, they are eliminated by the same chemical measures as used against Thrips; nevertheless it is a good idea to make sure that these insects do not get established, for their attacks can ruin the cyclamen for commercial purposes.

> Introduction

Leaf-rollers are insects in the family Tortricidae of the order Lepidoptera (butterflies and moths).

As with other moths, development is in four stages:

• egg
• caterpillar, with a well-developed head and strong mouth parts; 3 pairs of true legs in front and 5 pairs of false legs to the rear. (There are 4 or 5 phases of moult, when the caterpillar does not eat.)
• Pupa or chrysalis stage when the caterpillar is fully grown
• Adult (imago): moth or butterfly

 

As in the case of the Noctuids, it is the caterpillars which harm plants, especially those grown for their flowers and ornamental plants like the cyclamen.

The Leaf-rollers get their name from the fact that, with the exception of a few species, the caterpillars spin silk and live inside rolled-up leaves.

Others have other modes of life, living in flowers or in the hollow of stalks, in bark, inside fruit, &c.

> The Cabbage Leaf Roller (Clepsis spectrana, syn. Cacoecia costana)

The Cabbage Leaf Roller is a common species in central and northern Europe on herbaceous plants, including various garden and glasshouse plants. Under glass it is a ubiquitous pest, which attacks ornamental plants such as roses, gerbera, alstroemeria, azalea and cyclamen.

1 > Physical characteristics

1.1 > Adult moth :

• wingspan 15 to 24 mm (male often smaller than female)
• front wings ochre to yellowish, coloured patches on each wing which join to make a kind of “V” on the wings
• back wings light grey
• antennae thin and long

1.2 > Eggs :

• somewhat flat, orange, oval
• laid on the leaves in groups of around 10 to 70
• hatch 2 to 3 weeks after being laid.

1.3 > Caterpillars:

• 18 to 25 mm long
• deep green to black, lighter on the back
• head and prothoracic plate shiny black or blackish brown
• not very hairy
• four pairs of abdominal legs

1.4 > Chrysalis :

• 10 to 14 mm long
• dull black
• elongated shape

2 > Life cycle

Like the noctuids, the tortrix do not fly by day; they only move around after dusk.

Under glass this leaf-roller is found all the year round; there are 8 to 12 generations, which overlap. Outdoors, there are only two (a first generation between early June and July, a second in August and September) and an over-wintering phase for the caterpillars that hatch from the eggs laid by adults of the second generation).

3 > Damage to cyclamen

Caterpillars appear from May to September; they are heavy eaters, and feed on leaves, flowers, flower buds and stalks, especially from young shoots. In some cases the corm itself may be attacked. In addition to eating from these various parts of the plant, the caterpillar spins threads which it uses to descend to the ground when disturbed. It also weaves a kind of web which it rolls itself up in, and which rolls up the leaf also. The chrysalis stage also takes place in some of this woven material, inside rolled-up leaves.

The caterpillars also foul the plant with their excreta.

4 > How Cabbage Leaf-rollers spread

Outdoors, a first generation of tortrix moth appears from early June to July, sometimes even earlier. Tortrix moths are good fliers and so can quickly infest a glasshouse; and the invasion spreads from one house to another.

> The European Carnation Leaf-roller

Cacoecimorpha pronubana causes fearsome damage all over the Mediterranean region, and can sometimes be found on cyclamen as well as other plants.

1 > Physical characteristics

1.1 > Adult moth:

• average wingspan 20 mm
• rear wings from yellow to ochre to chestnut
• brown/chestnut patterns on the front wings

1.2 > Eggs:

• laid on plant stems and panes of glasshouses in groups of around 100 to 200, stuck together.
• each female can lay up to 600 eggs.

1.3 > Caterpillars:

• 20 to 25 mm long when fully grown
• colour variable from yellow to deep green or brown

2 > Life cycle

Generally there are four generations in a year. The adults appear from April to October, with a peak in May/June and another in late August/early September. The larvae of the third generation are usually the ones that over-winter.

3 > Damage that can be done

The caterpillars do considerable damage: destruction of terminal shoots, flower buds, young flowers... The result is a general slowing of growth and the destruction of many flowers.

They also soil the upper parts of the plant with their excreta.

> The Pear Leaf-roller

Epichoristodes acerbella arrived in France in 1971. The damage done is similar to that of the Carnation Leaf-roller; indeed it is hard to distinguish the two except by the appearance of the adults.

1 > Physical characteristics

1.1 > Adult moth:

• average wingspan 14 to 18 mm (male smaller than female)
• front wings yellowish with little dark dots (male) or yellow ochre (female)
• back wings greyish-white
• dark patch at the edges of the rear wings

1.2 > Eggs:

• light green in colour
• laid in clumps 1.5 mm across

1.3 > Caterpillars:

• 18 mm long
• green with a yellow stripe along the back
• shiny dark brown head

2 > Life cycle

The first adults appear from March to May; from June onwards, the generations overlap. Larval over-wintering is mostly in glasshouses, for sub-zero temperatures are lethal. Larvae also over-winter among the plant stems.

The caterpillar is most destructive of the plant.

3 > Possible forms of damage

They get through huge amounts of plant material.

Young leaves and older ones are browsed and holes are made until they are completely dried out. The threads and weavings make the leaves twist and roll up, and tie them to each other in webs of silk.

The caterpillars can also gnaw at the base of stalks, which makes the leaves on the stalks wither; and they attack flowers and flower buds also.

> Cnephasia incertana

Another tortrix, Cnephasia (probably Cnephasia incertana, the Light Grey Tortrix Moth) has been identified on cyclamen. Though they are also great eaters of plants, there is seldom a large enough population to cause severe economic damage.

> Biological control

• UV lamps in the glasshouses are a good means of trapping individuals and assessing the numbers present (for instance, with C. spectrana)
• use of commercial pheromone traps (sexual trapping) enables action to be taken immediately on the moths’ arrival (Carnation Leaf-Roller and Pear Leaf-Roller)
• it is also a good idea to gather up and burn all plant debris and to keep the area around the glasshouse weed-free.
• occasionally natural parasites (ichneumon flies) get into the glasshouse and attack the leaf-rollers; the infestation can then be much reduced. These little ichneumons are Trichogramma. They lay their eggs in a tortrix egg, and these develop in parasitic fashion, preventing the development of caterpillars.
• Bacillus thuringiensis has been used since the 1960s as a biological insecticide. The bacteria synthesise a protein-like crystal which acts as a toxin precursor. Caterpillars which eat leaves with bacteria on their surface die within 2 to 5 days of ingesting them. What happens is that when the bacteria enter the caterpillar’s gut, the enzymes there act on the precursor, transforming it into an active poison which breaks down the gut wall, and the contents spread through the caterpillar, upsetting its metabolism. What is more, the mouth parts of the caterpillar are paralysed within hours of ingesting the bacillus. Because it is specific, the bacterium is not dangerous for those insects not targeted by the poison (such as beneficial insects).

 

Carnation and Pear Leaf-rollers are susceptible to the poison types Bacillus Thuringiensis 3a and 3b.

 

There are many commercial preparations available, in the form of powders containing the resistant spores of the bacterium and the protein-like crystals.

As for the timetable for spraying, the instructions on the label should be followed; it has to be understood, though, that it is more effective against young caterpillars. Quick action then is needed to limit the damage, since caterpillars can go on feeding for some hours after ingesting the bacillus, and so the damage continues.

The effectiveness of this means of control depends on climatic conditions, and it cannot be used in all cases. For use on cyclamen, the climate in France is not damp enough.

> Chemical control

Chemical controls can be applied to the young caterpillars. When they get older and weave their protective webs and leaf-rolls they become considerably less accessible to plant protection chemicals.

A combination of egg-killing and caterpillar-killing chemicals as well as systemics should be used from May/June to November, for full protection.

It is important to treat early (as soon as the first moth arrives) and be sure to give the heart of the plant a through coverage.

 

The constant development of the regulations and homologations of phytosanitary treatment products, and the differences in regulations according to each country make it impossible for us to include updated information on homologations. Each producer will have to contact his local plant protection bureau to obtain the latest updates concerning the regulations and use of phytosanitary products. We strongly advise testing beforehand on a plant sample in order to measure the chemical’s activity (establishing the dose) and any effect on the plant (plant poisoning).

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