FORESTRY COMMISSION LEAFLET No.48 Price J s. 3d. net. 1964 e· NEEDLE-CAST OF PINE (Lophodermium pinastri)

By R. G. PAWSEY, B.Sc., M.Sc., PH.D.

Forestry Commission ARCHIVE

Figure 1. Severe infection by Lophodermium pinastri of Scots pine seedlings. Note the plantation, immediately adjacent to the seedling area, from which infection originated. NEEDLE-CAST OF PINE (Lophodermium pinastri)

Lophodermium pinastri (Schrad.) Chev. is the extent, insects) which cause similar symptoms fungus most commonly associated with to those produced by Lophodermium. needlecast of pines. This fungus has a wide­ The object of this account is to clarify the spread distribution in Europe and North conditions and symptoms most usually America, and has also been recorded as associated with infection by Lophodermium, causing severe damage to the Monterey pine, particularly as an aid to the decision whether Pinus radiata, in New Zealand. Many species or not control of the damage should be of pine are attacked, but in Britain, where attempted. Lophodermium pinastri is by far the most The most important physical factors causing common fungus on pine needles, infection is pine needle browning are extreme cold and most frequent on Scots pine, although Corsi­ exposure, and needles thus damaged are can pine is also commonly affected. So far, usually colonised by Lophodermium, or by a Lodgepole pine, Pinus contorta, appears to wide range of less important fungi. Under have considerable resistance to infection. The these conditions, Lophodermium is of little severity of damage caused by Lophodermium direct importance because most of the varies very greatly in different parts of the damage is caused by the initial adverse world. In continental Europe, it is regarded climatic factors, and unless these are followed as an important pathogen in both forest and by a prolonged period of other climatic in nurseries, while in Britain serious damage conditions which favour development of the is usually confined to nurseries. In North fungus, the damage due primarily to Lopho­ America, the fungus is generally considered dermium is likely to be limited. to be of minor importance. This variation THE FUNGUS AND DISEASE in the behaviour of the fungus is attributable SYMPTOMS to many factors such as climatic conditions, the species of pine grown, methods of forest Lophodermium pinastri is a member of the management and genetical variation of the Ascomycetes, belonging to the family Hypo­ fungus itself. dermataceae in which the sexually-produced fructifications are elongated and embedded GENERAL CONDITIONS in the host tissue and from which the spores CAUSING BROWNING AND are liberated through a longitudinal split in CAST OF PINE FOLIAGE the tissue above the fructification.

. Browning of pine and premature needle fall As is generally the case with ascomycete or cast can be caused by a great many agents, fungi, there is more than one type of fructi­ both physical and biological. Accurate diag­ fication in the life cycle. With this fungus nosis of the cause of the damage is often two fructifications occur: (a) the sexually extremely difficult, particularly as a com­ produced (perfect) fructification referred to bination of several factors may be involved. above, and (b) the asexually produced (im­ Infection by Lophodermium is much influenced perfect) fructification, known as the Lepto­ by climatic conditions which affect the disper­ stroma stage. Leptostroma was the generic sal of the fungus and its initial colonisation name given to the imperfect fructification of needle tissue, and also by climatic and other before it was discovered that two fructification conditions which either cause physical damage types occurred at different stages in the to the needles or have a marked effect on the development of the same fungus. general vigour of the trees. The same relation­ The imperfect Leptostroma fructification is ship also exists between the environment of a typical black pycnidium (a minute flask­ the tree and other fungi (and to a lesser shaped structure) of pin-head size, embedded

2 LEAFLET NO 48: NEEDLE CAST OF PINE

Figure 2. Pycnidia of Lophodermium pinastri at Figure 3. Mature apothecia of Lophodermium various stages of development on a Corsican pinastri showing the longitudinal split of the pine needle. epidermis above the fructification through which the spores are discharged.

3 in the epidermis of the needle (Figure 2). produced by Lophodermium and are a useful Within the pycnidium are produced numerous additional recognition feature. microscopic spores (conidia), which are The ascospores ejected from the apothecia released through the minute pore at the apex are extremely fragile structures and remain of the pycnidium. Unlike those of many viable for only a short while after discharge. ascomycete fungi, these conidia play no part The effective dispersal range of these spores in the dispersal of the fungus and at the is therefore very short and careful observations present time their biological function, if any, in British forest nurseries indicate that the is not known. The black Leptostroma pycnidia disease is not usually transmitted more than are produced early in the development of the 50 to 100 yards by these spores. in the needle and are the fructifications fungus Fresh infection is caused if the spores are most seen before needle-cast from commonly deposited on to pine foliage and experience tree the occurs. conditions which are suitable for their After the needles have fallen (and also, germination and the penetration of the germ infrequently, before this occurs) the develop­ tube into the leaf. Within the needle the ment of the perfect fructification, or apothe­ fungus grows by the production of minute cium, commences. Usually apothecia forma­ branched filaments, or hyphae, which even­ tion begins in the late autumn and continues tually cause the death of the tissue, which slowly through the winter, finally maturing results in needle browning. Generally, the in the spring or early summer of the following first browning symptoms of Lophodermium year. However, the life cycle of Lophodermium infection are seen during the late summer or is influenced by so many factors that fructi­ early autumn. After vegetative development fication production is often irregular, a fact of the hyphae within the needle tissue, which increases the difficulties of applying fructifications are then produced on the control measures at the most effective time. needle surface. The of are apothecia Lophodermium only Infection takes place most frequently on when are clearly recognisable they approaching first-year needles, but may also occur in or when have their maturity they discharged two-year or even older needles. Infected The mature are dark brown spores. apothecia needles are usually shed in the autumn or or almost black in or more colour, elliptical during the winter. Heavy infection may elongated in shape, and usually partially result in complete loss of the previous year's covered by the needle epidermis which has needles, but usually defoliation is only Under moist split longitudinally (Figure 3). partial; but if this occurs over a period of conditions the minute are ascospores (which two or three consecutive years, particularly narrow or filiform in are extremely shape) on nursery or newly planted stock, it may a short distance into the actively discharged have a serious effect on the growth of the air from the surface of the fructification. The trees. spores are carried by the slightest air movement away from the fructification and then passively FACTORS AFFECTING THE dispersed by the wind. SEVERITY OF INFECTION Infected needles which bear either the As mentioned above, any adverse con­ imperfect (Leptostroma) pycnidia or apothecia ditions which cause actual damage or a (or both) are usually completely brown in weakening of needle growth may lead to colour and narrow black bands (or dia­ infection by Lophodermium. Of much more phragms) generally occur at intervals along importance, however, are the climatic factors the length of the needle (Figure 4). These which directly encourage the growth and black diaphragms must be used with caution development of the fungus. In Britain, severe in the identification of Lophodermium as they infection is usually associated with cool wet are also produced by other fungi in pine summers, but mild autumn and winter needles. However, they are most commonly conditions may also be important. As is 4 LEAFLET NO 48: NEEDLE CAST OF PINE

Figure 4. Needle-pair of Scots pine infected by Lophodermium pinastri, showing apothecia, pycnidia, and characteristic black diaphragms.

5 frequently the case with diseases of this Lophodermium, it has never been considered nature, it is extremely difficult to disentangle necessary or practicable to apply control the influence of climatic conditions on the measures against this disease in plantation fungus from that on the host, and this is crops in Britain. On the Continent, however, particularly so with Lophodermium which may where the severity of infection is much greater, develop as a saprophyte on needle tissue large areas of pine forest are sprayed against killed by a wide range of agencies. attack by Lophodermium. In Britain, pines in plantation are seldom In nurseries in this country, prevention is seriously attacked, except at a very early undoubtedly the best method of control, and stage after planting. Nevertheless, needle under normal circumstances the raising of pine infection by Lophodermium may often be a can be confined to nurseries not immediately factor contributing to the eventual death of adjacent to older pine, and in this way a tree suffering from other diseases, insect avoiding, or greatly minimising, the chances infestations, adverse soil conditions, etc. of serious infection. Serious losses are almost entirely confined Providing that the materials can be applied to pine in nurseries, particularly where at the right time, effective chemicals are conditions favouring disease development available for the control of the disease in occur in two or more consecutive seasons. nurseries, but as mentioned before, the The most severe attacks have usually occurred irregular occurrence of infection by Lophoder­ in small pine woodland nurseries, i.e. nurseries mium presents difficulties in the correct timing established in strips or in small areas of open of fungicidal treatments. The copper-contain­ ground within large blocks of pine plantations ing Bordeaux mixture has long been the (Figure 1). In such sheltered nurseries, the traditional material in the control of Lopho­ high humidities in pine seedbeds and trans­ dermium, but this has now largely been plant sections probably enhance infection, but supplanted by zineb fungicides, which are undoubtedly the close vicinity of trees carrying both easier to handle and more effective. ubiquitous slight needle infection, and the Wettable powders containing 65-75 % zineb abundant source of spores from infected pine should be applied at about 4 lbs. powder per litter beneath the trees are of prime impor­ 100 gallons water per acre. The addition of tance. In Forestry Commission forests, the a wetting agent is advisable and should be raising of pines in pine woodland nurseries, ordered with the proprietary material con­ and as far as possible, in nurseries with pine cerned. The rate of application will naturally shelter-belts at the perimeter, has been dis­ vary with the size of the nursery stock con­ continued. Because of the short effective cerned and the aim should be complete dispersal range of Lophodermium ascospores, coverage of the needles with a fine spray. pine stock should only be raised in small In small nurseries which are adjacent to older nurseries with no older pine in the immediate pine, three spray applications are recom­ vicinity, or in sections of larger nurseries as mended, at the end of July, August and far as possible from any older pines outside. September respectively. In cases of earlier infection spraying should commence as soon CONTROL as Lophodermium infection is recognised, and Because of the relatively slight, and often be continued at monthly intervals until the secondary damage to older trees caused by end of September.

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