Common yew (Taxus baccata) and intermediate yew (Taxus x media) are extremely popular species that work well in our climate. Unfortunately, they are also often attacked by diseases and pests. As a result of infection, it happens that the wholeyew turns brown and loses needlesSee whatdiseases of yeware the most dangerous and which pests may appear on this tree. We suggest the best ways tofight diseases and pests of yew
Why does yew turn brown and lose needles?
Fig. pixabay.com
Physiological diseases of yews
Browning of yewdoes not necessarily mean that the plant is sick or is being attacked by pests. Physiological conditions may be to blame, and must be ruled out before starting to use pathogen control agents. Sometimes it is enough to improve the conditions of yew growing to get rid of undesirable symptoms.
Snow-free, cold winters are very dangerous for yewAdverse weather conditions mean that yew cannot take up water due to frozen soil and, additionally, is being dried out by cold winds. Then, the water management of the plant is disturbed, and this phenomenon is referred to as physiological drought. As a result,at the end of winter and early spring the yew turns brown and loses needles
To prevent yews from drying outduring dry winters, it is worth watering the plants abundantly in the fall, before the first frost sets in. If it is very dry, it is also possible to water plants in winter during periods of thaw, when the soil is at least partially thawed.It is also advisable to mulch the soil under the plants to prevent water loss from the substrate. The ideal material for sprinkling under yew trees is pine bark. In the case of small specimens, you can also cover the whole plants with, for example, a tunis. Autumn fertilizers rich in phosphorus and potassium, which are sprinkled under plants in August and September, are also helpful. They help the plants to prepare for winter (they support the lignification of the shoots and increase the frost resistance of plants).
Also, too low or too high pH of the soil adversely affects the development of yew. Therefore, it is worth knowing thatcis grows best in a slightly acidic substrate(pH 6.0-6.5). Improper fertilization, especially over-fertilization leading to soil salinity, can also cause yews to brown.
Yew fungal diseases
In the cultivation of yew, we most often encounter fungal diseases such as:
Rot rot- manifested by rotting of the root system. As a result, the needles of the yew trees change color and turn brown, and over time the entire plant withers. The diseased shoots show brown-red necrosis.
Yew phytophthora- attacks primarily the roots of the plant, and the effect of this are changes observed on the above-ground parts. Usually at the base of the shoot, just above the ground, you can see necrotic changes on the shoot.Yews grow slower, turn brown, and with time whole plants die.The cause of the disease is often too heavy soil and too dense planting. Under such conditions, phytophthorosis easily attacks various coniferous species. High temperature and high humidity are also conducive to the development of the disease.
Drooping tops of yew shoots may indicate gray mold but it may well be damage caused by late spring frost (photo taken in May)
Fig. Erazm, forum.PoradnikOgrodniczy.pl
Gray mold- the disease manifests itself as a gray, dusty coating on the needles and shoots, and the formation of watery, confluent stains.The spores of the fungus hibernate in the soil on dead infected plant parts, and symptoms of this yew disease usually appear in spring or the second half of summer. During intensive shoot growth, their tips turn brown and slightly bend. These are the first, quitecharacteristic symptoms of the appearance of gray mold in the yewsThe conditions favoring the appearance of this disease are high temperature and humidity. Gray mold usually attacks many other garden plants as well.
Dieback of yew shoots- this is an infection leading to browning and falling yew needles. Necrotic spots usually appear at the tops of the shoots and move gradually lower. In the fall, small black spots can be seen on the diseased branches, which are the fruiting bodies of the fungus causing this disease.
Fighting yew diseases
After noticing the first browning shoots on the yew , they should be cut to prevent further spread of infection.Whole plants should be sprayed with the natural preparation Biosept Active, which immunizes plants against diseases and stimulates their growth, which will accelerate the regeneration of damaged tissues.
It is also recommendedspraying and watering the plant with a biological fungicidePolyversum WP, which effectively treats plants affected by phytophthora and gray mold. Both of these measures can be used preventively andafter noticing symptoms of the disease on yew shootsDue to the different mode of action, however, Biosept and Polyversum WP should not be used simultaneously (choose one of them, and the second one should not be applied sooner than after waiting at least 2 weeks).
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If there is a need to use a stronger fungicide, it is worth reaching for the fungicide Scorpion 325 SC, whichcan cope with all the above-mentioned yew diseases This preparation is widely used and allows you to fight most fungal diseases on garden conifers.
Pests of yew
Apart from diseases, all yew species are also attacked by pests. The most important of them are listed below.
Yew tree cup- this is a pest whose larvae feed on the underside of the needles, and adult females feed on the bark of young shoots, from which they suck the juices. The yew bowl's foraging is accompanied by the secretion of a sticky substance, the so-called honey dew. The needles covered with it are a nutrient medium for the development of seed fungi, as a result of which the yew shoots become covered with a sticky, black substance.
Cisowiec cupcake
Fig. © PoradnikOgrodniczy.pl
When we notice that yew shoots have taken over the yew cup, a natural oil preparation Emulpar 940 EC should be sprayed.Spraying should be repeated after about 2 weeks. If this is not enough, you can use chemical insecticide spraying, such as Karate Gold and Mospilan 20 SP.In the following seasons, it is worth preventing the appearance of the cup on yews by performing oil spraying in the early spring. They destroy forms hibernating on the plant. The above-mentioned Emulpar 940 EC and Promanal 60 EC are suitable for this spraying.
Wielkopąkowiec yew- this pest occurs mainly on old, perennial yew specimens. It appears inside the buds and causes them to swell and die, and distorts the needles. The large yew tree hibernates inside the buds, which leaves in spring and feeds on needles. In May, it enters the newly formed buds, where it feeds and multiplies until late autumn. Twigs with swollen buds should be removed. In the past, it was also recommended to spray in April, during the spread of this uterus.Unfortunately, there are currently no pesticides registered to control unsightly ornamental plants.
Opuchlak pstrokacz- this extremely troublesome pest occurs not only in yews. It damages the needles by gnawing holes in them. Often, beetles also gnaw the bark in the area of the root neck. Adult individuals cause damage above the ground, while the larvae feed below the ground, causing numerous damage to the root system.To combat swelling , use Mospilan 20 SP or Polysect 005 SL.
MSc Eng. Anna Błaszczak
