Talven tuhot hedelmäpuissa ja marjapensaissa vuonna 1947

Lately there have been injurious winters for the cultivation of fruit in Finland in 1915—1917, 1927—1929 and 1939—1942. The winter 1946—1947 again damaged fruit trees and the berry-bushes gooseberry, currant and raspberry; this damage was most severe in the best areas for cultivation of fruit in Varsinais-Suomi (Ab) and Satakunta (St). In these areas about 10—75 % of the fruit trees and 75—80 % of the berry-bushes were injured or died. Slight injuries generally have been noted in Uusimaa (N), Häme (Ta), in the Valley of Kokemakiriver (St) and in the neighbourhood of Tampere (Ta). In southern Pohjanmaa (Oa) fruit trees and berry-bushes have been injured, too. The limit of the general injury-area is drawn through Vaasa (Oa), Alavus (Oa) and Virolahti (Ka). This limit closely follows the contour-line, to the west and southwest of which the depht of snow on March 15th was 30 cm or less (fig. 2). In the injury-area mentioned damage was such that the leaves expanded slowly in the spring, the flower buds, that appeared abundantly, opened slowly and the leaves and fruit were smaller than normally. In severely damaged trees the flower buds did not open, but dried up (fig. 1). In damaged trees, the cambium was generally brownish, the wood drier than normally, the roots, however, were generally white within and vigorous. The leaves of the berry-bushes expanded slowly in the spring; later in summer a many of the branches of damaged bushes died. These bushes generally grew new branches from their root. The damage to fruit trees and berry-bushes was due to the drying of the parts above ground in the spring, when the warm and sunny weathers induced activity of the vital functions in the plants. The soil was, however, deeply frozen because of the thin winter snowcover and when the thaw waters and rainwaters in May, with a little amount of rain, did not melt the ice, the roots were still in June in the frozen soil and did not absorb enough water from the soil, which even apart from this was too dry, to make up the evaporated moisture. Then the soft surface parts of the trees, rind and buds, were damaged. In summer the roots may perhaps have absorbed a normal amount of water, but because of the damage to the vascular system in the rind the flowing of solutions in the summer was not normal, and the shoots, leaves and fruits grew weakly. The damage to fruit trees was neither due to properties the variety and stock nor the age of trees (6). In the central parts of the country twigs of trees and sapling fruit trees were frozen because of the severe frost in winter. It can be estimated that 20—25 % of the fruit yield in Finland in 1947 was lost for the winter injuries

Keltamuumiotaudin tarttuvaisuudesta sekä sen ehkäisemisestä Paration-valmisteilla

The significance of fruit lesions of different kinds in brown-rot infection has been investigated. M. fructigena conidia were rubbed with a paint brush on the surface of apples uninjured and injured in different ways. All the uninjured fruits remained healthy. Slight injury done by copperlime 0.5 % (Cuprosan 3) and smallish spots, without cracking of the fruit, due to apple scab (Venturia inaequalis) were also unfavorable to the penetration of the brown-rot fungus. Infection in the former case was 0 %, in the later 7.1 % of apples inoculated. The inoculation of apples with severe corking and cracking resulted in 20.0 % infection and the inoculation of fruits injured by the codling moth (Carpocapsa pomonella) in 75.0 % respectively. All the fruits were infected when conidia were placed in a wound made with a knife-blade. It is thought that the susceptibility of lesions of different kinds to the brown-rot fungus is chiefly due to the moisture of the substrate and the air in the immediate proximity of the growing hypha. Spraying with the usual fungicides appears to be successful in controlling the brown-rot disease only if every fresh wound is covered (12). The control of apple scab and codling moth is also of importance, to avoid lesions made by these. It was thought that a compound penetrating the fruit tissues might be effective in controlling the disease through inhibiting the growth of mycelium in the tissues. One such chemical penetrating the plant tissues is diethylnitrophenylthiophosphate (E 606) (6). Parathion is found to inhibit the growth of Sclerotinia fructigena conidia (1). The fungistatic action on the brown-rot fungus of Parathion and some other chemicals penetrating the fruit tissues was investigated in the laboratory by dipping apples of the variety Charlottenthal or soaking them for 24 and 48 hours in the liquids. Every treatment consisted of 6 apples. Table 2. shows the daily growth of the brown-rot spot on apples treated in different ways and inoculated. The growth rate is shown in figure 2. Dipping, which corresponds in effect to one spraying (6), in 0.1 % mercuric chloride and in 0.1 % Cheminova-Parathion retarded the growth of the fungus. Soaking for 24 hours in Parathion reduced the growth greatly, soaking for 48 hours made the growth poor. Soaking in 0.05 % copper sulphate, 0.5 % tannin, 1 % ferrous sulphate and 0.1 % hydroquinone, too, retarded the growth of the fungus. The observations indicate that Parathion possesses an obvious fungistatic action on the brown-rot fungus and is possibly efficient in controlling it. For this reason a preliminary spraying experiment was carried out in 1950. The results indicate that Parathion was the preparation most successful in controlling the disease. This is due to the fungistatic action of Parathion and also to its insecticidal properties. Further investigations are needed into the significance of Parathion compounds in the control of the brown-rot disease

Talven tuhot hedelmäpuissa ja marjapensaissa vuonna 1947

vokKirjasto Aj-KWinter injury to fruit trees and berry-bushes in 194

Kevätvehnän vajaatähkäisyydestä

vokKirjasto Aj-

Keltamuumiotaudin tarttuvaisuudesta sekä sen ehkäisemisestä paration-valmisteilla

vokKirjasto Aj-KOn The Pathogenicity of monilinia fructigena (Aderh. & Ruhl.) honey and control with parathio