Mildew weather conditions

The percent increase in yield is often related to weather conditions. In dry years (1976) a relatively small number of fungicide cereal trials showed an increase in yield, but during wet years (1978) 60% of the tests showed yield increases. In long-term trials (4) in the Western region of Germany, seed treatments and foliar applications of triazole fungicides reduced crop losses from powdery mildew up to 25% (Table VI). ... 

PRIMARY INFECTIONS. The mildew fungus overwinters as mycelium in the buds. If there is very severe frost in winter, some of the infected buds may die off, as the bud scales are not completely closed. In the closed buds the mycelium produces conidia, which infect the young leaves, blossoms and fruit when the buds open. Infection may occur at the greenbud or redbud stage if weather conditions are favourable. The first symptoms of primary infections can then be seen on the leaves and petals at flowering. Apart from the climatic conditions, for mildew infection to develop the tree must also have susceptible tissue (very young leaves) available. The leaves acquire age resistance to mildew at an even earlier stage than they do to scab. 

WEATHER CONDITIONS FOR A MILDEW INFECTION. Optimum weather conditions are an air temperature of 15-25°C and over 70% relative humidity. 

Downy mildew is caused by the fungus Pseudoperonospora humuli (Miyabe and Tak.), G. W. Wilson. It was first observed in Japan in 1905 and in the United States in 1909. At that time hops were grown in the United States along the east coast and the incidence of downy mildew was one of the major factors which determined the transfer of the hop-growing industry to the west coast. In Britain the disease was unknown before 1920 but since then it has spread to all the hop-growing areas and some infection can be found in most gardens. Epidemics can readily occur under suitable weather conditions if control measures are not carried out. As discussed above, new varieties resistant to downy mildew are now available. 

Hemp can also suffer from fungi and diseases like Fusarium wilt, septoriosis and gray mildew are found especially in weather conditions promoting these diseases. Sometimes, especially if hemp is grown several times on the same stand, in may suffer from a parasitic plant, branched broomrape (Orobranche ramosa L.) [14]. Virus diseases may also sometimes attack hemp. 

It is generally understood that a suitably flame retarded fabric should retain this property under conditions of wear, wash and weather. Furthermore, the flame retardant component should not effectively alter the fabric characteristics including hand, drape, adsorbency, strength and durability. In addition, this component should not adversely modify other chemicals designed to impart color, size, mildew resistance, water repellency and the like. Finally, the incorporation of a flame retardent treatment in the processing cycle of the fabric should not burden the user with excessive cost. 

Leaves covered with white powder. Cause Powdery mildew. Powdery white or grayish fungal patches grow on upper leaf surfaces of plants subject to poor air circulation or hot, humid weather. As the disease spreads, leaves become distorted and ma drop off. Powdery mildew is more severe when growing conditions are unsatisfactory. 

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