Scale insects belong to the order Homoptera, the family Real scale insects (Diaspididae). All insect coccids, and there are about 3,000 species, of which the majority are more than 2,600 species of scale insects, the rest of the worms and felts are herbivorous, feed on plant juices, voracious and dangerous pests.
All scale insects have pronounced sexual demorphism - males and females differ in structure, very often when describing a new species of scale insects, scientists characterize only females, since it is the feeding females that are noticeable on the stems and leaves of plants, while males live very little, only before mating, then die. In some species of male scutes, very little is produced - only 2-3%, it is difficult to detect them.
What the shield looks like
Females have no legs, no wings, no eyes, no antennae, but there are well-developed mouth organs of a piercing-sucking type. While females are young, the shield is soft and insects can move around. When the shield ripens, they become motionless. Outwardly, most scutes common on indoor flowers are similar - the body is oval or rounded from 1.5 to 2 mm long. The body under the shield is white or pale brown, segmentation is not pronounced. The scutellum in mature individuals can cover the entire surface of the body, or partially, be strongly convex, hemispherical in shape, or flattened. The color of the shield is yellowish brown, dark brown, consists of the secretory part and larval skins. In different phases of the larvae, the skins can be of different colors, so the shield is often heterogeneous in color, for example, the outer ring is golden brown, the central one is dark brown. Among the scutes common in garden crops, larger species are found: with a pear-shaped or teardrop-shaped body up to 5 mm long.
In males, the oral organs are reduced, but there are eyes, fully formed limbs and wings. The body is segmented into head, chest and abdomen. Males are mostly white and fluffy. Sometimes reddish, red-gray, light orange. They also have a shield, only very small.
Shield eggs are oval in some species, elongated oval, usually white or light gray, gradually darken to light brown. Eggs are very small, about 0.1-0.3 mm, look like worms through a microscope.
The larva of the first age is called a vagrant - it has a flattened oval body, up to 0.3 mm long, yellowish in color, three pairs of legs, antennae, eyes. In many species of scutes, the color of the larva can be understood in which it is reborn. So, in the mulberry shield, the vagrants are white and red, females grow from white, males grow from red.
The larva of the second age is larger. Her body is white or gray, the back of the body is usually darker, the dimensions reach 0.5 mm. By this time, the female larva has no legs, antennae, eyes. It is distinguished from an adult only by the size and lighter color of the shield.
Among several thousand species there are shields of a slightly different appearance - in some females with an almost transparent body, the shield is invisible, they seem to be glassy; others have very irregular bodies, like blots; still others have a rich black shield. The morphological stages of development in scutes may also differ, for example, some tropical scutes do not have an egg stage.
It makes no sense to describe a specific type of shields, since you have seen them in a photo or live, you will not confuse them with anyone.
Scutellum development cycle
Scutes have a pronounced life cycle. But tropical scale insects and pest insects of temperate latitudes have differences. They are associated with climatic conditions.
In nature, it looks like this: the female, after mating for three months, hatches eggs and feeds on the juice of plants. Three months after fertilization, she lays many eggs, according to various sources from 250 to 500 pieces, after which she dies.
Scale insects living in temperate climates, for example, apple comma-shaped scale, have the following stages of development:
egg>> larvae of the first age (vagrant)>> larvae of the second age>> males and females>> egg
Females have an elongated and wide-rounded end of the shield - under it is the entire clutch of fertilized eggs, the body of the female herself simply dries out, freeing the house for the children. Our winters are harsh and all oviposition is preserved under the shield. By the end of May, when the average daily temperature is about + 8C, vagrants hatch from eggs and begin to actively populate plants, mainly young, slightly lignified branches, young growth. The cycle of development from a vagrant to a sexually mature female averages three months. Then mating occurs. The number of males in the population is approximately 20-35%. After fertilization, males die. Oviposition begins in August. Thus, the development cycle is approximately 1 year: 9-10 months of egg maturation, 35-60 days of larva, 3 months of female. In southern latitudes, these types of scutes can have time to form two generations per year.
In tropical species, these are, for example, California scale insects, slightly different stages of development:
larvae of the first age (winter)>> larva of the female and larva of the male>> parthenogenesis *>> mating>> larvae of the first age (vagabonds)>> larval diapause>> larvae of males and females of the second age>> adult males and females
The shield of females is usually round - they do not need a house for egg laying, females of many species of tropical shields lay larvae. Larvae of autumn birth winter in shelters (under the bark, axils of leaves). In spring, vagrants come out of hiding, quickly fall in love with the juiciest places and develop larvae into the next stage, adults - males and females. By the time of mass maturation of females, the flight of males begins (it lasts several days). Males are few, their number from the total population is no more than 8-9%. Mating occurs, after which the male dies.
* Males do not reap much because the scutes have a parthenogenesis phenomenon - this is virgin reproduction, when sexually mature females grow up without fertilization (mating with males).
The cycle of development of the shield from the awakening of vagrants to a sexually mature female averages a week or two. Part of the vagrants in the middle of summer goes into a state of diapause - rest. This helps the shield to survive unfavorable conditions, since in summer vagrants die from prolonged drought or heavy prolonged rains. Diapause can last from several weeks to several months. Most of the larvae turn into females. And it takes about a month to develop them. In males of some species of scutes, the development cycle includes an additional two stages: pronymphs and nymphs. Thus, the entire development cycle is approximately 60 days.
I must say that there is no classification of scale insects by climatic types, here it is given only for clarity, in order to see the difference and diversity in the development of individual species of pests. Some scutes common in subtropical regions, for example, the false caliphal scutellum, also have an egg stage, only then larvae. Usually oviparous flaps differ in the shape and size of the flap - it is wide enough, like a Vietnamese hat, rounded or pear-shaped. In addition, in some species of scale insects, not eggs winter, but females in a state of diapause.
The number of links can also be different: for example, females can have two larval stages, males - three.
From the point of view of indoor floriculture, the danger of scutes is that due to parthenogenesis - the offspring of females without fertilization, scutes can multiply, all year round, giving out about 5-6 generations, the process of generational change is continuous. At the same time, males are extremely rare among indoor shields, but if they appear, for some reason they are very frightening. Someone begins to think that this unknown is a terribly gluttonous creature. In fact, the development cycle of scale insects, with or without males, is no different. By themselves, males do not harm plants - they simply have nothing to eat. In fact, male shields hatch for the sake of a single mission - fertilization, therefore, all they have is eyes, wings and genitals.
Damage from shields
All shields cause great harm to plants, in gardens in 3-4 years they can completely destroy an entire fruit tree. In countries with a warm climate, in agricultural regions, when some types of shield are detected (for example, mulberry), strict quarantine is introduced. For this period, the export of seedlings and seedlings is strictly prohibited. Fruit trees and shrubs, stone crops and tea plantations are treated with pesticides.
In indoor conditions, shields, having settled on a plant, will also lead to its death as soon as possible. Shields come to our house with infected flowers from the store, planting material (soil), tramps are brought in by the wind.
At the place of suction of the shield, yellow spots appear on the leaves, they grow in size as the cell juice is sucked out, then the leaf completely yellows or turns brown, twists and falls off. The plant stops growing, the branches are exposed, then the whole bush begins to dry out and the plant dies. In addition to leaves, the shield damages the fruits of citrus fruits (tangerines, lemons and oranges), the ovaries fall prematurely, and the flowers dry out.
Another sign of the appearance of scutes is sticky discharge on the leaves. Scutes produce a sweet liquid - pad, it covers the stems, petioles of leaves, leaves, buds and fruits. Sooty fungus and dust stick to it.
Shield control measures
As soon as you find a shield, something similar to brown plaques on the stems, petioles, axils and leaves themselves, immediately isolate the plant, and also check all the plants that stood nearby. Adult scale insects are protected from insecticide exposure by the scale, but can be removed from the plant mechanically.
To do this, it is best to use a cotton pad and sponge for delicate leaves or an old toothbrush (with soft bristles) for denser leaves. Soak in soapy solution and thoroughly wipe each leaf on both sides, as well as the stems. Even if it seems to you that there is no pest on some leaf yet, you need to treat the whole plant, otherwise one surviving larva, and after a few weeks the whole plant will be sprinkled with a shield again. For washing leaves, any detergent for dishes (aos, fairies, etc.), laundry soap, tar soap, green soap is suitable. Whisk the thick foam and leave it on the leaves for 30 minutes, then rinse with hot water (the water temperature is permissible up to 50 degrees - the hand is hot). Hot shower - 2-3 minutes. If soap washing and hot shower procedures are carried out once a week, then you can get rid of the shield without chemicals.
Without washing, plants that cannot tolerate such a procedure have to be sprayed with insecticide. But a single treatment will not completely save them from the shield. Since the female's shield protects her and the oviposition from contact insecticides, you need to soak the plant in solution, lower the entire crown into a bucket of chemicals, or use irrigation with systemic insecticides - Aktara or Confidor - these are the drugs of choice.
Of the contact drugs against the shield are effective:
- neonicotinoids: Actara, Tanrek, Apache, Confidor, Colorado, Golden Spark, Mospilan,
- organophosphorus compounds: Actellic, Karbofos, Alatar, Iskra, Fufanon Nova, Kemifos, Novaction, Anticlesch and others,
- hormonal insecticides, juvenoids - regulators of insect growth and development, for example, Admiral (pyriproxyfen),
Treatment with contact and intestinal contact insecticides must be repeated at least three times, with an interval of 7 days, in order to ensure the destruction of the generation of pests of larvae newly hatching from eggs. In addition, the frames and glass of the window, the windowsill where the infected plant stood, must be wiped with alcohol-containing liquid or dishwashing solution.
If you live with young children, relatives, patients with asthma or allergic diseases, if you do not have the opportunity to thoroughly ventilate the apartment after applying chemicals, or if you are pregnant, do not spray plants from insecticide, high hazard class (carbofos, actellic), there are less dangerous ways, read the following recommendation.
Flea and tick repellents against shield
In addition to the above insecticides, anti-flea agents, where the active substance is imidacloprid, and/or fipronil and cypermethrin, are effective against the shield. These are remedies for fleas, and for lice, ixodid ticks from a veterinary pharmacy: Avanpost drops, Advantix and others.
If you have only one plant infected with a shield, buy the smallest dosage - drops for indoor dogs or cats. If you have a severe infection with a shield, you need to treat several plants, buy drops for large dogs weighing more than 25 kg.
How to process: dilute the contents of the pipette with drops with water, there will be no complete dissolution - an emulsion will be obtained. Dilute a small pipette into 500 ml of water, more per 1 liter of warm water. Then, with the resulting emulsion, thoroughly moisten all the leaves of the plants on both sides, try to get the solution into the sinuses, cover both the stems and petioles. Be sure to moisten the top layer of the ground. Leave the solution on the plant to dry. With the same solution (or just soapy) wash the windowsills and glass. When the plants are dry, ventilate the room thoroughly. You do not need to wash off flea and tick remedies, if the smell remains, then you can wash off the emulsion the next day.
One treatment with flea and tick repellents is usually sufficient. But if the lesion was very strong, you need to repeat the treatment after 7 days.
If it is not possible to repeat spraying, if there are no oil drops, another option: make up all pots of flowers in large garbage bags (120 liters), tie the bag so that it is inflated, but not to the end - leave a gap. Spray the bag thoroughly with flea and tick spray, such as Bolfo spray. We do not recommend using dichlorvos - it has a very short-term effect and high initial toxicity. So, we stick the aerosol in a bag and press the sprayer for 4-5 seconds. Carefully tie the bags, leave it for a day. Pests die from suffocating.
It is best to carry out all procedures outdoors (take out the plants in boxes, make them in a basin) or on the balcony.
Effectiveness of actara against shield
Among the florists, there was an opinion that the actara is not very effective against worms and scale insects. Where did it come from: one of the sites described the active substance of actara - thiamethoxam, then the quote: "the low biological effectiveness of thiamethoxam in relation to scutes is due to the fact that it quickly spreads through the phloem, but weakly penetrates into succutilar cells, the contents of which are sucked out by scutes."
In fact, a typo was made in the text, and everyone quoted it safely. In this case, we mean sukuticular layers - i.e. layers of covering tissues of leaves, stems and fruits. Indeed, thiamethoxam, when watered with actara under the root, penetrates the phloem of the leaves, but only a very small part of it penetrates into the integumentary tissues. But when sprayed with actara solution, about 60% of thiamethoxam absorbs the main tissues of the leaf (mesophyll), 10% - the epidermis and about 30% remains on the waxy layer of the cuticle. I.e. the concentration of the active substance in the epidermal layer is high enough to poison the pest.
Thus, on indoor flowers, actara against the shield is quite effective, but the effectiveness will be much higher if you simultaneously pour the soil in pots with actara solution and spray it on the sheet. In addition, it should be noted that the waiting period when watering the soil with aktara solution is 2-4 days, and when spraying - from 1 hour to 1 day.
Insecticide consumption rates against shield
- Admiral - 6 ml per 10 liters of water, spraying,
- Aktara, VDG - 8 g per 10 liters of water spraying, 1 g per 10 liters of water - watering,
- Actara, CS - 1 mL per 10 L of water, watering,
- Actellic - 2 mL per 1 L of water, spraying,
- Spark Golden - 1/4 tablet per 2 liter pot - buried in the soil,
- Karbofos - 1 g per 800 ml of water, spraying,
- Confidor - 4 ml per 10 liters of water, spraying, watering.
- Fufanon - 10 ml per 10 liters of water, spraying.
Folk remedies - medicinal herbs, garlic and onion infusions from scutes practically do not help.