Spiders mites are one of the most dangerous pests that infect plants and cause great losses in crops. The danger of spiders is due to the following:
1 – The small size of mites spiders, as the length of some adult individuals reaches five millimeters, as in the family of worms, where it is difficult to see and therefore its resistance is delayed.
2- The rapid multiplication of spiders and their presence in large numbers on their host plant, as the number of their generations sometimes reaches 28.
3- The large number of eggs that one female lays in one generation, to about 100 eggs.
4- It is difficult to detect spiders on infected plants except after damage has occurred and the infection has spread.
5- Confusing injury with spiders and diseases. innate.
There are three families spread, the red spiders Tetranychidae, followed by about 13 genera and about 35 species.
The second family is the spider family, Tenuipalpidae, followed by about 9 genera and about 22 species.
The third family is Eriophyidae, followed by about 18 genera and about 44 species.
The most important dependent spiders Red spiders – Tetranychidae –
This type of spider is characterized by its speed of movement, and it has the ability to secrete spider threads, the most important of these spiders.
First: the ordinary red spider with two spots –
Tetranychus urticae Koch –
The common red spider with two spots, is characterized by the following:
The common red two-spot spider Tetranychus urticae infects deciduous fruit trees such as grapes, plums and apricots, as well as field crops such as legumes and vegetables, as well as cucurbits, eggplant, strawberries, and ornamental plants such as roses, and medicinal and aromatic plants.
* The red spider is generally found on the lower surface of the leaves, and in the case of severe infestation, it can be found on the upper surface of the leaves.*
The red two-spot spider is distinguished by the presence of two brown spots on its dorsal surface, and the body color is greenish-yellow, bright red or dark red.
The life cycle of the red two-spotted spider Tetranychus urticae.
is an egg, then a larva, then a first nymph, then a second nymph, and finally the adult insect.
signs of spider mites.
The number of Tetranychus urticae the red two-spot spider increases rapidly and in a short time, as the duration of one generation is about a week, and the reproductive efficiency of the female reaches about 10 eggs per day.
The red two-spot spider can tolerate pesticides and also produce pesticide-resistant strains.
* The infestation of the red two-spot spider increases at moderate temperatures as well as at high temperatures to a certain extent.
How to infect the red two-spot spider in the field:
* The infection is transmitted by the red spider with two spots by bringing infected seedlings.
* The infestation of the red two-spot spider increases in the presence of weeds on the farm, especially hibiscus weed, currant weed, as well as blackberry and blueberry weed.
* The presence of castor trees on the farm helps the spread of the red spider with two spots strongly.
* The movement of the red spider with two spots on the soil helps to spread it on the farm at a remarkable speed.
The red two-spotted spider sorts the threads, which helps it move from one plant to another.
* The red spider is also transmitted by the workers working in the farm, as well as by the wind, and it is transmitted with irrigation water.
Symptoms of Tetranychus urticae a red two-spotted spider infection.
Small yellow spots appear on the upper surface of the leaves.
* In the case of severe infection with the red spider with two spots, an earthy appearance is seen on the lower surface of the leaves, and this is the result of spider threads and dust collected on these threads.
* In case of severe infection, red spiders with two spots appear on the upper surface of the leaves as well as on the lower surface of the leaves and the leaves on both surfaces are covered with dust. The color of the leaves changes from green to yellowish-green and then to light brown
The fight against the red two-spot spider:
* The red spider with two spots is combated when 5 individuals appear on the leaf and chemical control is carried out using the appropriate recommended pesticides or using mineral oils such as royal oil.
* In the case of the use of predators or vital enemies of the red spider with two spots, the fight begins when the number of spider members reaches from one to three individuals on the affected leaf.
* It must be ensured that the red spider with two spots is eliminated and an estimate of the level of infestation after the control, and in the event that any number of spider members appear on the leaves
Second: brown citrus spider: Eutetranychus orientalis Klein
This type of spider lives on the upper surface of the leaves, and also infects the fruits.
Citrus spiders also infect all citrus trees such as lemon, orange, grapefruit, tangerine, and lemongrass.
Symptoms of a brown citrus spider infection:
* Yellow spots appear on the leaves that turn brown, and with the increase in the severity of the infection, the leaves dry and fall.
* The brown citrus spider is most infested during the month of July and August, and the infestation is absent during the month of February.
* The infestation of the brown citrus spider increases with the high temperature of the air in the summer and decreases with the decrease in the temperature in the winter.
Third: red mango spiders.
The red mango spider is dark red in color, and it infects mango trees and pomegranate trees, as well as sweet trees (apricots, plums, and peaches).
Symptoms of a red mango spider infection:
* The most important symptom of infection with the Sternochetus mangifera is its appearance on the lower surface of the leaves, and with the intensification of the infection, the infection also appears on the upper surface of the leaves.
* The infection begins with the appearance of yellow spots on the lower surface and with the intensification of the infection
Infestation extends to the upper surface and extends to the entire surface of the leaf, then the yellow spots turn red to brown, then the leaves dry and fall.
* Oligonychus mangiferus infestation intensifies during July and August with high temperatures as well as high air humidity.
Fourth: European red spider – Panonychus ulmi
This type of spider infects fruit trees, especially apple, peach and pear trees.
The maximum population of these spiders reaches during the months of July, August and September.
* Females lay eggs on the leaves and absorb plant juices, then yellow spots appear that permeate the entire leaf, and thus the efficiency of the leaves that dry and eventually fall off.
At the end of the autumn, the females lay their winter eggs on the branches to meet the unsuitable environmental conditions. To combat these spiders, they are sprayed with a mineral oil during mid-February.