hi I find myself a hedge full of mites to the point that the trunk has become black. It was pruned a month ago and the new shoots are still clean, but other nearby hedge plants begin to present the same problem. long lasting and not harmful for the lawn and can tell me what creates these infestations thanks
mites are small arachnids, almost invisible to the naked eye, which grow on the foliage of plants, especially in conditions of dry air and poor ventilation; the black stem and the strong infestations of which you speak to me do not seem to indicate the development of mites, but rather of cochineal with half a grain of pepper, also considering that you say that they are not present on the shoots. The mites are arachnids, and not insects, and have typically summer development, because they love the scorching heat and the dry climate, generally in winter they develop only in the apartment or in the greenhouse, and in any case they attack the foliage or the buds still green and tender , and not wood.
I don't think it is even aphids, because they develop instead in conditions of high humidity, and 2012 is now showing itself as a rather dry year with spring, with scarce infestations of aphids, which over all love buds, and therefore now you would have them on new twigs and not on stems.
So, I think it is cochineal, an insect that hibernates quietly on our plants, not caring about the cold, the frost, the snow.
These looking insects could remember strange aphids, even if very often, especially at the end of winter, those we see on plants are not insect adults, but small bags containing eggs, hundreds of eggs, ready to hatch on arrival of hot, or it is larvae, also ready to grow when the heat arrives, to produce hundreds of eggs; it is therefore clear how important it is to remove these pouches before the eggs hatch, leaving the scale insects to flood the garden.
These insects are decidedly unpleasant to eradicate, because they form various types of badges, dark and rigid, white and fleshy, pink and waxy, depending on the species to which the cochineal belongs which has decided to settle in our garden.
The dark cochineals, also called cochineal with half a pepper grain, belong to the Saissetia genus, and form stiff and dark, almost black, badges, which in strong infestations may be present in hundreds, even on the stem of plants affected by this parasite.
Against the scale insects white oil is used, purified mineral oil, which has the power to dissolve the badges under which insects and eggs nest, and kill them; it is used late winter, usually added to a pyrethroid insecticide, and yes, it carries out a second treatment with only white oil in late summer.
After the treatment it usually happens that insects, even if dead, remain in position, and therefore it often happens that useless treatments are repeated, on plants infested with dead insects; to avoid this event, before practicing the treatment, remove some badges with your nail and you will see that they have a sticky consistency underneath. About ten days after the treatment, he breaks some other shield, to check that dead buckets are inside.
These insects develop in conditions of drought and poor ventilation, therefore they tend to develop much at the end of winter and in autumn, if the climate is not very rainy, and above all on the very thick and dense hedges or shrubs, where the air does not circulate good; a thinning pruning of the foliage tends to decrease the number of scale insects present on the plants.