Currant - is in second place in terms of distribution in industrial plantings after wild strawberries. This is due to a number of factors, this is frost resistance and sufficient drought resistance and ease of propagation (just stick a part of the shoot into the soil) and the cheapness of planting material, coupled with a large and increasing number of varieties every year. However, currants have an abundance of diseases and pests and it is simply impossible to grow it without fighting them. Today we’ll talk about one of these pests, the gall aphid, which causes quite significant damage to currants, affecting the appearance of the plant and its yield in a negative way.Signs of gall aphid damage on currant leaves.
What is the harm of currants from gall aphids?
It is worth starting with the fact that the gall aphid for the most part attacks precisely the “colored” currant, that is, red, white, burgundy and the like, but the golden currant and black currant (including those with green fruits) damage to a much lesser extent. Apparently this is due to the structure of the leaf, in the “colored” currants, the leaf blades are somewhat more tender, therefore it is easier to pierce them and suck out the juice from them.
As a result of the active life of the aphids, very ugly tubercles or swellings appear on the surface of the currant leaf blades, it seems that the currant is affected by some kind of disease, but if we turn the leaf over, we notice insects - this is gall aphid.
Gall aphid, sucking juice from currant leaf blades leads to severe deformation. This insect usually selects the growth of the current year with the most tender leaves on them, full of life-giving juice. This suggests that aphids harm not only this year, but also have a negative impact on the harvest of the next year, because new shoots actually stop growing and the bush does not develop, therefore, the potential of the harvest of the next season is reduced.
Description of gall aphids
The gall aphid, or the leaf gall aphid, or the redcurrant gall aphid (Cryptomyzus ribis) is a representative of a large aphid family of more than four thousand individuals distributed throughout the globe. Gall aphids are found everywhere where currants grow. Gall aphids, in the absence of currant plantations or the leaf mass of this shrub suitable for nutrition, can live on such crops as mint, sage, oregano, lavender, thyme and nettle, this should be borne in mind and, if possible, do not combine the plantings of these crops.
Externally, the gall aphid is not much different from the aphids "familiar" to us, which affects not only shrubs, but also trees. This is a small insect having an ovoid shape of a body, reaching a length of a couple of millimeters, for the most part not having wings and painted in a pale green-yellow hue. If you look closely, then on the body of the gall aphid you can notice small hairs.
In one season, four to two dozen generations of gall aphids can form, usually the higher the temperature in summer, the more gall aphids and, consequently, more harm from it.
Only one individual aphid can give birth to hundreds, and sometimes even more of its kind.Gall aphid on a leaf of currant.
Why is gall aphid called “gall”?
In fact, when the gall aphid sucks the juice from the leaves of the currant, the plant does its best to heal the holes formed from its injections and forms a tissue that looks like a growth - gall, that's the name. If you do not fight with gall aphids, then the life-giving forces of the plant may not be enough to completely heal all wounds, and it can even die by drying out.
Among other things, like all sucking pests and gall aphids can transmit various viral infections and, when a leaf of currant is punctured, infect a plant with the virus, then even in the case of successful destruction of gall aphid colonies, one will also have to deal with a viral infection, which is usually more difficult.
Gall aphid life cycle
The categories of gall aphids are very interestingly distributed, a kind of hierarchy or, rather botanically, polymorphism. Polymorphism means that different generations of gall aphids can be very different from each other both phenotypically and produce completely different actions throughout their lives.
For example, the founder aphid, she emerges from a laid egg and is a kind of mother of future generations of gall aphids, the most interesting thing is that she no longer lays eggs, but produces live aphids, that is, gives birth to them throughout the entire warm season. Only female individuals are produced that produce subsequent generation.
Most aphids are represented by a group of female individuals who do not enter into sexual relations, they feed on the juice of currant leaves, have no wings, and, therefore, practically do not move (usually only within the same plant), and those that are parthenogenetic hatch the same individuals .
The next group is gall aphids, called settlers, they have fully developed wings and are activated when the aphid colony grows so much that it needs another place to feed, since the current plant is no longer able to fully feed all individuals. In this case, aphids with wings fly to the next currant plant and produce a new generation of aphids, actually creating a new colony.
Gall aphids also have intermediate generations, for example aphid strips, which can be either males or females without wings, but capable of having sexual intercourse and not giving birth to full-fledged individuals, but laying fertilized eggs.
And finally, there is a generation of bisexual aphids whose essence is to ensure the survival of the species, usually they lay eggs in a variety of places, including weeds located in the immediate vicinity of the currant, in the bark of the same currant and similar places. Of these eggs, aphid founders usually appear.Affected gall aphid bush of currant.
The process of development of an individual gall aphid
After laying eggs, they can last up to 250 days in this form, sometimes a little more, usually this is enough with a large margin to survive the cold period. As soon as spring arrives and the air warms up, the aphid founders begin to emerge from the eggs, which quickly move to the nearby currant plant.
Typically, the mass reproduction of gall aphids occurs during the flowering period of the culture. Gall aphids are most striking in the leaf mass at the very beginning of summer (often this beginning or mid-June). At the end of July, when the main leaf mass of the currant becomes coarse, the surviving individuals are divided into plants that we described above, a generation is born that has both male and female sexual characteristics, which are then returned to the currant plants for egg laying. This usually happens at the end of August, sometimes in the middle of this month.
Gall aphid control measures
Firstly, you need to take a closer look at plants and knowing the biology that we have described quite carefully, pay more attention to any changes in the leaf mass of currants. If you notice even slight foci of deformation of the leaf blades, you need to immediately take measures, having first made sure by turning the leaf over that it is really a gall aphid - you will see small red spots, this is galls.
The very first way is to expose the currant bush to high temperature water. To do this, bring the water to a boil and as soon as possible, until the water has cooled too much to pour over the bush with it. Often this is done even before the appearance of the leaf mass, in order to destroy the ovipositor of the pest, otherwise you can damage the leaves and even more so the inflorescences.
Manual aphid assembly
If there are few affected leaves of currant (literally 4-5 on each plant), then they can be torn off or cut off and burned beyond the territory of the site. If one branch is affected and tubercles on most leaves swell on it, then the whole branch can be cut, but the cut must be insulated with paint or garden var.Signs of gall aphid damage on currant leaves.
Folk remedies to combat the gall aphid
The most common folk remedy is a decoction of tobacco dust. Usually they take ten liters of water (great if it is rain) and pour 250-350 g of tobacco dust there, after which they bring the solution to a boil, remove from heat, close with a tight lid and put in a dark room for three days. After this time, you need to strain the broth well, add a piece of antibacterial soap, mix everything well, season the spray bottle and treat the plants, trying to get on the bottom surface of the currant leaf.
If necessary, such treatment can be carried out even during the entire warm season, alternating in 5-6 days, just do not process the plants during the flowering period, so as not to harm pollination and a couple of days before harvesting.
An infusion of marigolds is the second most popular means of combating gall aphids on currants. To obtain it, you need quite a few flowers - about 500 g. Marigold flowers can be chopped in any way convenient for you, pour ten liters of rainwater and bring to a boil, then remove from heat, cover with a tight lid and put in a dark room for two days.
After this period of time, you need to add a piece of antibacterial soap to the infusion (it, as in the first case, will play the role of an adhesive), strain everything thoroughly, fill in the spray gun and treat the affected plants with it, trying also to get to the bottom of the sheet. Treatments are carried out at the same time as when processing decoctions of tobacco dust. Doses can be different, depending on the number of affected leaflets, the main thing is that they are all moistened.
Mustard was also used before, but as it turned out that it was the strongest allergen, it was decided to abandon its use.
Chemical measures against gall aphids
If alternative control measures do not help, you can start using chemicals, but it is not advisable to immediately use environmentally harmful insecticides, pay attention to biological preparations first, they may help. When using biological preparations, remember that this is also a kind of “chemistry”, therefore you should not refuse to use protective gloves and a respirator and should be carried out in sunny, cool, but still weather.
Biological preparations are made from spores of bacteria, as well as various parts of fungi and even elements of viruses. As soon as they enter the body of the gall aphid through the proboscis, with which it absorbs the juice, it paralyzes, and sometimes completely destroys its intestines, the aphids die. For example, we give drugs that gardeners respond positively to, this Bitoxibacillin, Actofit and Avertine. Remember, however, that when applying them, you also need to carefully read the instructions on the package, in no case do not exceed the dose, but also do not save, otherwise there simply will not be the proper effect of their use.
If the gall aphids on the currant are so many that they can’t even cope with simple preparations, then you can use insecticides, this is usually a serious chemistry, so you must wear protective equipment, find out what should be the distance to the nearest bee farm and a stocked lake or river and strictly in calm weather, it is better to start processing early in the morning or late in the evening.
Remember that in this case it is better to use drugs that are approved for use, not to use old ones that are “lying around” on the shelf. The first treatment is preferably carried out at the stage of bud opening (if the currant plantation was severely affected in the aphids last season), it is desirable to do the second treatment after harvesting (if the gall aphid is rampant this year). But of course it all depends on the drug - read the instructions, maybe the drug allows you to perform processing at other times.
Gardeners respond well to drugs: Actelik, Confidor Maxi, Wofatox, Calypso and Proteus.The dying leaves of currant after the defeat of currant gall aphids.
Gall aphid prophylaxis
Well, in conclusion, we will talk about prevention against gall aphids, because any disease, including a pest, is better not to let go to your site than to waste your energy in order to expel an intruder.
It is better to start preventive treatments in the early spring, before opening, and it is better even before the currant buds swell, and you can continue in the late autumn (November) after all the leaves from the plant fall off. Quite effective are the treatment at this time of both plants and the part of the drug Nitrafen. Nitrafen very effectively fights against the ovipositor, but it can harm the leaf mass and even more so the flowers. Usually a 4% solution of the drug is used, diluting 4 ml in a bucket of water. This amount is enough for 20 adults or 40 young currant bushes, if you use a spray bottle.
Do not forget about folk preventive measures - plant marigolds along the perimeter of the plot, sow chamomile or calendula.
Be sure to carry out weekly weed control, starting in May and ending in mid-September. Remember that the carrier of the pest, a kind of "rest house" or "maternity hospital" for gall aphids is cleaner, it simply should not be on the territory of your site.