The red spider on the vine: a very present plague
The red spider is a tetraniquid and polyphagous mite that affects numerous crops, including the vine.
It is present in Spain, especially in areas with a mild climate, where sometimes the greatest damage occurs. When the heat arrives, winegrowers must be attentive to this mite to prevent them from losing the harvest.
Next we will see what is the red spider, what is its cycle and how we can combat it.
What is the red spider on the vine
The red spider is known by different names (red mite, spider…). Although its name indicates that it is a spider and belongs to the arachnid class, it is not a spider itself, but a polyphagous mite (Tetranychus urticae) that feeds on the plant, absorbing fluid from the cells, causing chlorotic stains in the leaf bundle.
It is one of the most abundant species spread throughout Spain. In fact we can find it in Valencia, La Rioja, Alicante, Almería, Navarra and Murcia.
You can finish a plantation in a short time thanks to its high reproductive potential, its short life cycle, the high rate of development they have and the rapid dispersion capacity it has.
Evolution and cycles of the red spider
The biological cycle of the red spider is holometabolous and consists of 4 stages of development: egg, larva, two stages nymphs (protonym and deutoninfa) and adult.
Spiders spend the winter in the form of eggs, which are deposited around the buds and leaf scars, also at the base of the thumbs and even on the arms and trunks. Before the end of the revival the first females prepare to deposit in the leaves the first summer eggs. The hatching occurs between March and April, coinciding with the sprouting of the vineyards.
From the eggs hatch three-legged larvae that evolve to the protonymph and deutoninfa stages, in which they become four-legged. The female is oval and dark red, with hairs that come out of whitish bumps. These larvae invade the buds to feed and reach the adult state in 15-20 days. The life of the females can last from 20 to 28 days, in the case of males only 14 days.
It can measure from 0.4 to 0.6 mm. The male is somewhat longer, paler and smaller. Given its size it will take a magnifying glass to see how much the vine is attacking.
The eggs are spherical and smooth, amber or orange. Each adult female can lay 100 or 120 eggs, with a rate of 3-5 eggs per day. In optimal weather conditions you can complete your cycle in 9 days.
Although egg laying can vary depending on the climate. Thus its main activity occurs in summer and in hot and dry seasons. In the Mediterranean area, with mild temperatures, they can even be active throughout the year, causing significant damage.
During spring, summer and autumn lives on the leaves, which comes to colonize them from the base to the tip of the branch. On them there can be from 7 to 9 generations.
The red spider has a high aggregative tendency and the usual thing is that it develops its colonies on the underside of the leaves, where they produce an abundant web that protects them from predators, caresses and of the own time.
Symptoms and damage of red spider plague on the vine
You have to be very careful to avoid the attack of the red spider, because it is one of the diseases of the vine that can make us lose the entire plantation.
On the leaves, the symptoms spread throughout the limb. In it appear necrotic dotted marks surrounded by a discoloration of the leaf. Early attacks can cause very serious damage such as falling leaves, reduced plant growth and drying buds.
In summer, the attacks cause the loss of chlorophyll and defoliation which causes a decrease in the sugar content of the must and may even have an impact on the vegetation of the following year.
The damage caused by the red spider on the vine is caused by its food activity. To feed, he inserts his stylus into the tissue of the leaf, thus sucking the contents of the epidermal cells.
Then the cells collapse and die when emptied which causes chlorotic spots to form on the leaves, decreasing in turn the activity of the plant at photosynthetic level and transpiration rate. If the infection coincides with times of high temperatures, it can cause severe defoliation.
Damage occurs on the one hand on the shoots and on the other on the leaves. In the shoots they cause bad shoots that delay the vegetative development and diminish the productive capacity and quality of the crop. In the leaves it makes the end of summer have a leaden color.
Treatments to control or for the pest
As with other diseases of the vine, when talking about treatments we can differentiate between ecological treatments or cultural practices of prevention and chemical treatments.
It is essential to clean the environment of weeds such as correhuela or mauve, in which the spider hides before proceeding to attack the surrounding plantations. Although it may be the case that these weeds also serve as a shelter for the natural enemies of the red spider, so eliminating them would mean the disappearance of these natural predators.
Healthy plant material from approved nurseries should also be used.
Do not abuse insecticides or powerful insecticides that can kill the surrounding fauna.
Another means of control is to burn the pruning wood, as it may contain winter eggs.
In order to eliminate the pest of the spider on the vine it is necessary to perform the corresponding treatments, always choosing the products according to their ability to control or eliminate the pest as well as depending on the side effects they may have.
There are many chemicals such as pesticides that can kill the spider but it has also been the case that this mite is very skilled at developing some resistance to chemicals.