THE AGRONOMIST ANSWERS ON HOW TO GROW AND CARE FOR PLANTS
Cyclamen spp. (Family Primulaceae)
The section is dedicated to plant problems.If you wish to write to our agronomist in order to have an answer on an unclear situation or a difficulty concerning your plant, it is necessary that you indicate:
- what plant it is;
- where it is located (inside the house, on the terrace, in the garden, etc.);
- the type of exposure (full sun, half-light, etc.);
- how long has it been in your possession;
- the general state of the plant;
- the frequency of watering;
- how often it is fertilized and the type of fertilizer used;
- any pesticide treatments carried out;
- the symptoms it presents and the parts of the plant affect;
- any foreign presence (insects or other).
If possible, send a photo, but in any case, take care to be very detailed in describing the overall state of the plant. The address to which everything is forwarded is: [email protected]
Antonio P. from Milan / Italy asks:
Good morning Antonio,
So white and regular, also considering the good state of health of the plant, I would say that it is some drop of that "milk" that jasmine releases if a leaf or a branch breaks.
Just try to scratch them off.
If it were to be leaf lesions, let's resent.
Cyclamen, integrated defense strategies
Among the important floricultural productions of the summer period, together with the poinsettia, the cyclamen certainly stands out.
A crop present in practically every floricultural and garden company, it requires a rather long cultivation period and can be subject to various problems, in terms of defense, affecting both the root system and the leaves.
Although historically it is one of the most "bombarded" productions by classic synthetic products, today an integrated production is also possible here thanks to the use of microbiological products, mites and beneficial insects.
Starting from the "hidden" part, that is from the root system, pathogenic fungi can be of various origins but the attacks of Fusarium spp. they are generally the most frequent.
On the other hand, as regards the foliar apparatus, the main fights are aimed at thrips, lepidoptera, mites and even aphids.
The microbiological industry today makes available a myriad of products designed to improve, protect and promote proper root development, thanks to the use of mycorrhizae, rhizosphere bacteria and antagonistic fungi.
The big common denominator that groups all these products is one and only: prevention.
There are excellent products on the market for the protection of the root system, but it is precisely a protection and therefore curative effects cannot be expected in case of forgotten use in the correct period, which is identified with the time of transplant.
Among the various products, for the prevention of Fusarium spp., in particular those based on the now well-known mushroom Trichoderma spp. and the bacterium Streptomyces spp ..
Both are able to rapidly colonize the roots of the host plant showing an antagonistic action against pathogenic fungi, but also act through other modalities such as competition in the substrate, hyperparasitism, production of antifungal metabolites and stimulation of root hair production.
The main protagonists of the integrated struggle are represented by predatory mites and a parasitoid insect: Amblyseius cucumeris, Phytoseiulus persimilis, Aphidius colemani.
Amblyseius cucumeris is a predatory phytoseid mite used for the control of thrips (Frankliniella occidentalis, Thrips tabaci and others) on various horticultural and ornamental crops. This predator, with a pear-shaped and hyaline body, is small but very mobile and is able to use other food sources, including pollen, which it searches for by actively exploring the plant.
Phytoseiulus persimilis is a predatory phytoseid mite successfully used all over the world, for the biological control of spider mites (Tetranychus urticae), on various horticultural and ornamental crops, both protected and in open field. The females, with the pear-shaped body of bright orange color, are slightly larger than a red spider and very mobile. P. persimilis it is characterized by a high research capacity and is able to explore large surfaces. Its use is successful thanks, in addition to its rusticity, to the fact that it feeds on all stages of red spider, from egg to adult.
Aphidius colemani (hymenoptera braconid) is an important parasitoid used for the biological control of different kinds of aphids, mainly including Aphis spp. is Myzus spp. in vegetable and flower crops. A. colemani it is a solitary parasitoid, which carries out the larval cycle inside the body of the aphid. The females, endowed with a high capacity for research, frequent the settlement sites of the aphids and once the aphid has been identified they lay an egg inside it. The parasitized aphid does not die immediately, but is slowly emptied from the inside until it swells, transforming itself into the so-called brown-hazelnut "mummy". An adult individual will then emerge, which in turn will actively seek other prey to parasitize.
On the other hand, there are no mites or insects useful for the control of the main lepidoptera that affect cyclamen, but products based on Bacillus thuringiensis they are effective and fully compatible in an integrated pest management program.
The integrated pest management strategy starts from the first days of cultivation. As mentioned above, interventions with products for the protection of the root system must be carried out immediately after transplanting, possibly with the first wetting, in order to protect the crop and prevent attacks by pathogens.
In the event of subsequent periods of stress, the great summer heat is the most striking example, these products can be repeated to help the crop recover.
The introduction of useful organisms can take place later, but here too the key to effective use is use in prevention.
The preventive launch of A. cucumeris it is essential: thanks to its polyphagia, the mite will be able to reproduce and assert itself in the crop even in the absence of thrips and will be ready to feed on it as soon as the thrip attacks the cyclamen.
- persimilis it is instead an obliged predator and therefore it feeds only on red spider, its introduction is recommended in any case shortly before the expected period of attack by the red spider, perhaps with launches with a low number of individuals per square meter in order not to leave the “discovery” crop.
The introductions of A. colemani generally follow the same reasoning as for the introductions of P. persimilis, however, the aphid being an indispensable site for its reproduction.
In order to translate these hints of integrated pest management into effectiveness, the specialized technician plays an essential role in the planning of the launches and will follow the producer in the various stages of cultivation by carrying out technical visits to check the correct execution of this strategy.
If necessary, the technician will also be able to indicate the right plant protection products to be used compatibly with the organisms introduced.
Good cultivation practices should never be abandoned: it seems trivial but a plant in good "health" conditions, just like us, is less susceptible to attack by pathogens.
To control thrips, you can benefit by placing blue or yellow sticky chromotropic traps and periodically check the adults of thrips in order to have an indication of the population trend.
For aphid and red spider, on the other hand, the monitoring must be more accurate and it is necessary to directly control the crop. In these cases, greater attention is paid to those points where infestations historically start, such as the proximity to doors or side openings or to other crops that attract the same type of harmful organisms.
> Symptoms observed
Symptoms generally begin in July and bear many similarities to those of another plant pathogenic fungus, the Phyllosticta cyclaminis.
After the germination of the spore, the mycelium produced penetrates the plant through the stomata placed on the underside of the leaves. Later, it develops in the intercellular spaces.
Symptoms occur 10 to 16 days from the onset of the infection.
On the leaf limb, yellowish-brown to reddish spots will appear. These spots, round or polygonal, are oriented in the direction of the ribs. Relatively numerous, they can cause the leaf to dry out. Secondly, raised black dots form in the center of the leaves. These are the fruiting of the fungus from which the spores responsible for other infections will come out.
Stains may also appear on the petiole which, in the case of the bulbs, will be oily and brown in color.
The development of the fungus is favored by mild and humid climatic conditions.
> Life cycle and general morphological characteristics of thrips
The life cycle of thrips is divided into 6 stages:
- 1 egg stage
- 2 larval stages
- 2 nymphal stages (a pre-pupal stage with the appearance of wings and a pupal stage)
- 1 adult stage
For all species, the duration of development depends on the temperature. To simplify, we can state that, in a certain temperature range (neither too high nor too low), the duration of the development is inversely proportional to the temperature. For the Californian thrips, for example, the duration of the development cycle is 15 days at 26 ° C and 44 days at 20 ° C.
Above 35 ° C, the cycle stops.
The eggs are individually deposited in the parenchyma cells of the young leaves, petals and tender stems. A female lays 60 to 100 eggs throughout her life.
After incubation, larvae appear, relatively similar to adults. They have a rounded, oblong body and move thanks to several pairs of legs. The larvae are aptere.
The two larval stages feed abundantly.
At the end of the larval stage (from 8 to 15 days) the nymphosis process begins.
The pupae remain motionless, often in dark corners, such as the ground, where the larvae drop to give life to nymphosis. After 2/5 days, the adults leave.
The color of the adults varies from light yellow to brown, depending on the species of thrips. The body is flattened, with a length between 1 and 2 mm depending on the species. Males are generally lighter and slightly smaller than females.
They are equipped with 3 pairs of legs. The wings folded on the back, are narrow and pointed and the long hairs that cover them allow a gliding flight that can vary, depending on the species, from a few seconds to a few hours. Females have an ovipositor.
Life cycle and appearance of cyclamen Tortricide
The adult female has a length of 12 mm and is yellow ocher with darker markings. The male is slightly smaller and elongated, with more evident signs and lighter in color. They both have two brown markings on each wing. When the moth is at rest, the two signs that come closest to each other take on a "V" shape. At rest, the wings are kept folded almost horizontally on the body. The antennae are thin and of medium length. Audlts fly when it's dark.
The yellow eggs are laid in groups ranging from 10 to 90 units and are covered with a gelatinous layer. They are found on the upper page of the leaves, especially on the main veins or in the depressions of the epidermis. The caterpillar has a dark green to black cephalic capsule and a prothoracic shield. The body is dark gray with sometimes light colored side stripes. The ventral surface is lighter than the dorsal one, with hairs protruding from the lumpy points which are lighter in color than the rest of the body.
In general, the caterpillar has a rather dull appearance. When found in pepper fruit, however, the caterpillars are much lighter and have dark side stripes. The larvae are relatively thin and can reach a maximum length of 25 mm. They are slightly shaggy and have four pairs of pseudo-legs. They can produce clusters of silky filaments in which they hide or live within fruit or flowers. It is these filaments that cause the leaves to curl. Many of these filament clusters are hollow, so caterpillars are thought to make a series of silky shelters during their development. The pupa is about 1 cm long and is brown in color. The transformation into a pupa takes place within the cluster of rows.
Symptoms of damage
The larvae (or caterpillars) feed mainly on leaves, flowers and buds. The largest larvae spin a silk that unites the newly emerged leaves. As a result, subsequent growth gives rise to an untidy set of coiled leaves presenting with large feeding holes. Caterpillars can also penetrate the plant: young specimens tunnel from the opening bud to the growing end, while the later stages drill a hole in the bud and empty it, causing wilting and death of the bud itself or of the growing apex.