![]() ![]() Closer spacing of trees also increases profits per acre. Christmas tree growers may feel that premium trees must have heavy density foliage. Problem trees are also most likely genetically predisposed to the needle cast disease, reducing the likelihood that other control measures will be effective. These may need to be culled the following year when symptoms are expressed. Remember that there may be trees which are infected but haven't shown symptoms. ![]() Usually only a few trees are initially diseased and would need to be culled. Cutting and burning trees that have the worst symptoms can significantly reduce the number of spores available to spread and infect other trees. If the other three strategies are employed, fungicide treatments are typically not necessary. Once a needle cast has been positively identified in your Christmas trees, there are four control strategies to prevent disease spread: 1) cut and burn problem trees, 2) increase air movement around trees so foliage does not stay wet as long, 3) maintain good fertility, and 4) apply accurately timed fungicide sprays. Only in this way can fungicide applications be properly timed to be effective in controlling the disease. Since fungi produce spores at different times of year, it is important to know which fungus is the true pathogen. They do not cure the plant after infection has occurred. Most fungicides protect the plant from getting infected. Involving your county extension agent in this process is essential.Ĭontrolling Needle Cast Diseases Skip to Controlling Needle Cast Diseases This may require sending multiple samples over time to a diagnostic lab to catch the fungus when it is producing spores. Correct diagnosis of a needle cast fungus is essential for control. For many needle cast fungi, spores can still be produced after the needle has dropped to the ground. The spores produced by the needle cast fungi eventually erupt through the needle, allowing spread of the disease. Defoliation over several seasons can also cause branch or even tree death. In some instances, needle cast fungi grow down into the stem, causing death of the stem or branches. Others can produce symptoms on the previous two years of needles. Some needle cast diseases can cause symptoms on current year's needles. Infected needles shed the year after they were first infected. Symptoms are expressed the following spring, and the spores are produced later in the season. The fungi infect developing needles in the spring. Most needle cast diseases have a one-year cycle. ![]() Saprophytic fungi will also be present if the needles were killed by other means such as fertilizer burn or root rots. These fungi are called saprophytes, since they live on dead tissue. ![]() As soon as the pathogen starts to kill the needle tissue, other fungi that are not true pathogens start to grow. For many species of fungi, spores are only produced after needles have dropped from the trees.Īnother common problem in diagnosing needle casts is that the pathogen may not be the only fungus present in diseased needles. In fact, most needle cast diseases will infect needles one year, and not exhibit symptoms or produce spores until the following year. Unfortunately, needle cast fungi produce spores infrequently. The symptoms are similar to low pH, poor nutrition, fertilizer or chemical burn, and even root rots.Ĭorrect diagnosis of a needle cast requires microscopic examination of the size and shape of the spores produced by the fungus. Needle cast diseases are often difficult to diagnose. Diagnosing Needle Casts Skip to Diagnosing Needle Casts ![]()
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