Panonychus ulmi

Panonychus ulmi, better known as Red little spider of the fertile ones and the grapevine, is a phytophage of the fruit plants and the grapevine which lives on the leaves and on the buds. The females are 0.5 mm in diameter; they are of red pave color with whitish markings on the back, near the insertion point of the dorsal bristles. These white markings distinguish these ragnettis from similar spiders, such as Tetranychus urticae. The males are smaller than the females and of a lighter color; the baby spiders are a yellow-orange. The eggs are easily identifiable by their vibrant red color, and the larvae, which hatch in spring, are yellow-orange. The spider causes a distinctive puncture on the buds and on the leaves, which causes a bronze discoloration; the leaves then dry and fall from the plant. Under a careful examination, the plants infected by these spiders exhibit a whitish-grey powder in addition to the holes in the leaves and buds. They can finally be noticed some small and weary plots sericee, whitish, shed on the two leaf pages to confirmation of the colonization from the acaro. On the productions the damage is the direct consequence of the serious filloptosis that they are verified in correspondence of the acaro. The Panonychus winter as egg on the woody organs and it completes 7-8 generations a year.

Struggle

The struggle against the Panonychus ulmi effects him doing first some fundamental considerations, that are also worth for the other acaris:

1) the Little spider is become a very serious problem, particularly when starts to fight it;

2) before effecting the relative treatments it is essential to appraise the consistence of the biocoenosis, particularly:

- it is had to verify the presence of his effective natural inspectors, among which: the Coccinellidis Stethorus punctillum, the Antocoridis of the kind Orius, the predatory Acaris Amblysesius andersonii and Kampimodromus aberrans;

- it is had to verify the presence of the Red little spider and to compare his population with the raiders, to determine the thresholds of intervention.

On the fertile ones the threshold of intervention is equal to around the 50-90% of leaves infested by the mobile forms of the acarus; it is had to consider however that it doesn't need to intervene in presence of a congruous relationship acaris natural phytophagous/antagonist. Among these it dresses again particular a lot of importance the Stethorus punctillum, that can be enough for every 2-3 leaves one of it, to dissuade the intervention. For some varieties of however sensitive to the Bruson, induced also from the presence of acaris, the threshold corresponds to the first infestation. On the grapevine the threshold to be considered is:

- equal to around 60-70% of infested leaves, in spring;

- equal to around 30-45% of infested leaves, in the summer.

The chemical products which can be used for specific plants are:

- for grapevines: Fenazaquin, Clofentezine, Tebufenpirad, Fenpyroximate, Pyridaben, Dicofol, Fenbutatin-oxide (neanicide), Exitazox;

- for apple trees: Fenpyroximate, Tebufenpirad, Pyridaben, Azocyclotin, eventually mixed with Exitazox (active also on eggs and citotropic) or with Clofentezine (eggcide), for different stages of development;

- for other fruit trees: Exitazox, Tubufenpirad, Fenazaquin, Fenbutatin-oxide, Fenpyroximate, Pyridaben, Clofentezine;

- for the Drupacees: Dicofol, Fenpyroximate, Pyridaben, Exitazox, Tebufenpirad, Fenazaquin, Clofentezine.

The use of Brominepropilate is recommended, also recorded on the grapevine and Peach tree, active on eggs and hatched insects. On however, apple tree, grapevine and citrus fruit the insecticide-acaricidal Flufenoxuron, chitino-inhibiting active translaminare works well on eggs and juvenile stages. To prevent serious problems resulting from an infestation of the ragnettis, it is oppurtuno to perform a suitable struggle against the other fitofagis avoiding the use of insecticides to ample ghost of action, ex. Piretroidis that "they sterilize the biocoenosis" killing important inspectors of the acaris, what the predatory Hemipterans, Gall midges and others. Using species-specific insecticides, such as Clofentazine, is preferable when dealing with infestations, in order to protect the beneficial insects, such as Acaris Fitoseidis and the Stigmeidis, which themselves help protect the plants against the spiders..

Translation

The phrase "Panonychus ulmi" occurs as such in the following languages: English, Italian.

Translation(s) in other languages: German: Rote Spinne, Croatian: Crveni pauk, Polish: Przędziorek owocowiec.