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It is usually easier to deal with pests of cacti than with diseases, but they cause considerable harm, sometimes they irrevocably destroy valuable specimens. The result of damage by any pests is a slowdown or suspension of growth, the absence of flowering or the shedding of buds and flowers. A little later, various spots or bloom, similar to a crust, sticky streaks, grains, blackened or bleached areas, etc. appear on the stems of cacti.
Mites on cacti
The most common pests of cacti. They are microscopic and difficult to spot right away. There are many types of herbivorous mites, the most dangerous is the red flat mite. The females of the tick are about 0.3 mm brick-red in color, with an angular-ovoid body. Males are rare, and it is almost impossible to notice them - they are even smaller. Eggs are bright red 0.1 mm. Larvae are broadly oval, red, with three pairs of legs. As a result of a lesion with a red tick, spots appear on the stem of a cactus, as if covered with a rusty bloom. There is no web. The bad news is that the affected parts of the plant, covered with spots, remain disfigured.
Control measures. Ticks are not insects, but arthropods, so ordinary insecticides do not work on them. Acaricides are needed to kill ticks. The problem is that many ticks develop poison resistance very quickly. Pests that survived the first treatment may be resistant to repeated treatments. Therefore, at the first sign, it is better to use a strong drug immediately. It can be actellic, neoron, fufanon, apollo, oberon. It is necessary to dilute the drug according to the instructions. It is advisable to carry out two treatments with different drugs at intervals of a week. See acaricides for details. How to process: spray the cactus stem with a solution of acaricide and water the soil, even in the root zone.
As a prophylaxis against ticks, wiping the cactus stem with a brush dipped in a solution of alcohol and acetone, ratio 2: 1, or garlic and onion tincture is effective. For a full article on mites on indoor plants and methods of control, see the Herbivorous mites page.
Pests have an oblong (oval in outline) body, 2 to 5.5 mm long, usually gray in color, with more or less pronounced white hairs. On the sides of the body, many legs are clearly visible. There are viviparous species, such as Spilococcus cactearum - actually a cactus bug, there are those that lay eggs. The female spends egg-laying in white fluffy cocoons, similar to cotton wool lumps.
Females and larvae harm plants. Worms are dangerous because they can be discovered too late. There are many species of pests that have different preferences. Some usually settle in the roots and the root zone - the bugs of the genus Rhizoecus are small, up to 3 mm adults, when they multiply strongly, they can be seen on the stem. But most species of worms are superficial pests, mainly concentrated in the areoles, between the papillae and ribs of cacti, as well as in the root zone. Shelter worms are especially fond of - at the very beginning of the hit they hide in the upper layers of the soil, between the stems of cacti, if they grow in a group. When they begin to multiply intensively, they crawl over the entire surface of the cactus. The movements of the worms are slow, but noticeable movements.
Outwardly, small shaggy white bodies of pests look like lumps of cotton wool, foam crumbs, in the root zone as if sprinkled with flour or looks like a white salt coating. It is bad that cacti are lagging behind in growth, the stems turn pale, lose their intense green color. In some species, for example, in mammillaria, the stems grow thin, thinner, become lethargic. With severe damage, cacti may die. Very often worms come to our house with purchased cacti, so take a closer look at the newcomers.
Control measures. It is best to deal with worms with systemic drugs - watering the soil with a solution of an actara or confidor. The active substance is absorbed from the solution by the roots, and the plant juices become poisonous to pests. If the worms are concentrated locally - on the roots and neck, root baths can be used. For this, the roots of the cactus up to the root collar are kept in hot water at a temperature of 50-55 ° C for 15 minutes. You can rinse the roots in actellic solution, but the effect of the drug should not be long.
Here's what experienced florists recommend, Colleague:
- It is necessary to thoroughly rinse the roots from the worm. Under hot water - start warm and gradually remove cold water. Nothing will happen to the cactus, but the worm will be boiled down. Not a single white spot should remain!
- Lather the Fairy roots. hold in the foam. Rinse thoroughly.
- Dip the roots in a phytoverm solution - very strong, like thrips. Hold for 15 minutes.
- Dry the cactus.
- Throw out all the contaminated soil, pour over the pot with boiling water, wash with a comet.
- Plant the dried cactus in a new soil, into which add 2 packs of crushed activated carbon, perlite and vermiculite.
- Process (spill) the entire collection with phytoverm.
- Put the cactus back in place.
Shield and false shield
These pests are much less common on cacti than ticks or worms. The scale insects are visible on the cactus stem in the form of small, only 1-2 mm flat scales. Reddish to dark brown in color, scutellum hard. False shields differ in that even older individuals have a more transparent or paler body, from gray-yellow to light brown. The essence does not change - these creatures deplete cacti, suck out cell sap, bringing the plant to complete death. The scabbards move very slowly, for our eyes they sit motionless in one place. If there are a lot of scale insects, the cactus stem is covered with their sticky secretions.
Sometimes scale insects can be confused with brown specks formed by a fungal or bacterial infection. In this case, try to pick up the stain - if it is a scabbard, it leaves a wet stain, but underneath it is a whole skin. If it is not possible to knock off the shield - a stain in the tissues of the epidermis, then this is not a shield, but some kind of disease and not an insecticide is required, but a fungicide.
Control measures. The scabbards must be removed from the stem with a cotton swab dipped in alcohol, if the thorns allow. If the thorns are very thick, it is better not to touch the insects, but to water the cacti with a solution of actara or confidor. These are systemic insecticides - the pests will die, dry out, and you can simply shake them off with a brush. Sometimes one treatment is enough, but it is advisable to repeat watering with actara in a week.
These are worms of microscopic size - no more than 0.5 mm in length, translucent, can only be seen under a microscope. Nematodes are quite rare; they prefer moisture-consuming, loose and nutritious soils. The problem is that it is difficult to spot it right away. Signs: growth retardation and stunting, change in tissue color - the stems become paler, sluggish, thinning of the top of the cactus. The main sign is the appearance of spherical swellings or growths (gall) on the roots:
Control measures. All affected parts of the roots are cut off, the whole plant is treated with alcohol, and the roots are given a hot bath. For this, the cactus roots, peeled from the ground, are dipped in hot water at a temperature of about 70 ° C to the root collar for 30-60 seconds. Or stand at 50 ° C for 15 minutes. After the root bath, the entire root system is sprinkled with crushed coal. If we talk about chemicals, it is believed that agents based on imidacloprid are effective against nematodes - these are Confidor (1 g per 5 liters of water), Tanrek, Vermitic. Immerse the plants in the solution completely and completely and the roots and stem. To prevent the appearance of nematodes on a healthy plant, you can sterilize the substrate. In any way - steamed in boiling water, heated in the oven or microwave.
Any disease and appearance of pests is much easier to prevent than to cure. There are special hygienic procedures that should become mandatory for a novice cactusist, especially if the cactus is not one, but several, or a whole collection. Hygienic procedures include regular spraying of cacti with a very fine spray bottle, disinfection of planting containers, tools for transplanting, grafting, picking, etc. Sterilization of soil and sand before transplanting. Alcohol is used to disinfect the instrument; in the absence of it, it can be replaced by simple scalding of boiling water. Pots and bowls are washed and also poured over with boiling water. The soil and sand are fried in the oven, or spilled with a solution of potassium permanganate.
All wounds on the stems or roots of a cactus caused by pests, or, after removing parts of the roots, are sprinkled with crushed coal or sulfur.
Diseases of cacti