Diseases and Insect Pest Control (I) Disease 1. Guava Blight (1) Symptoms of Damage The current economic cultivars of Taiwan's guava are not resistant to disease. Once the guava fruit trees are infected with Bacterial blight, they are first created by the plants. The disease appears in the tip, and the buds of the affected branches cannot be unfolded and turn dark and dark. When the growth was stopped, the unfolded leaves near the sprouts showed a lack of fertilizer, similar to the symptoms of magnesium deficiency or iron deficiency. From the whole plant as a whole, the leaves of the branches of the lesions are light and dark, with no vitality, and the reflections are weak and easy to distinguish from the leaves of healthy plants. Branches of rickets are easily defoliated at the later stage, and the disease is more obvious. The disease will gradually develop downwards. By branch bifurcation, the branch moves from the bottom to the other new branch, which leads to the onset of grafting, eventually leading to the development of the stem base and causing the whole plant to wither. In the late spring and summer, the field develops milder disease, and the illness is also mild, but it is serious in autumn and winter. At present, new lines of guava, such as pearls, are more susceptible than Thailand. Rhizoctonia solani has (types of spores, long ovals and short ellipses, all of which are unit cells, conidia at 36 degrees, the best germination, do not germinate at 16°C and above 40°C, and the oblong spores are shorter elliptical The germination rate of spores was 2-3 times higher. The mycelium grew best at 30°C. It could not grow above 40°C or below 16°C. The optimal growth temperature was 26-34°C. The sporulation temperature of diseased tissues was 16 The highest sporulation was observed at -36°C, humidity also affected sporulation, and the higher the humidity was, the more spore production was, and the humidity was lower than 28°C, the sporulation was very difficult. Bacterial blight is present near the vascular bundles, and chemical control is extremely difficult, so the work in the field clearing garden is extremely important, and it should be avoided that the infected dry branches remain in the field and become the source of secondary infection. Prevention methods: 1Improve irrigation and drainage facilities in orchards to keep the soil Good permeation performance to reduce the spread of mycelial bundles.2 Slope land orchards can be planted with Pythium acuminata, not only to make good soil and water conservation, but also to regulate the relative micro-humidity in the orchard, and also to prevent the spread of bacilli bundles. Replanting new seedlings near the plant to reduce The source of pathogenic bacteria and the opportunities for survival.4 Carefully select healthy and strong seedlings to avoid selecting seedlings in the nursery near the diseased plants to reduce the chance of infecting pathogens.5 Applying organic fertilizers must be done after fermentation Fertilize and cover the soil to avoid excessive application of alkaline fertilizer such as lime, etc. 6 The pruned leaves should be kept away from the neck of the fruit tree, so that the site can be well ventilated, and the diseased plants and diseased branches can be excavated or cut off to reduce the infection of the pathogen. The chance of onset.7 Timely use of fungicides to sterilize, such as pruning the entire park, spraying pesticides, effective pharmaceuticals include: benomyl, fungi, organic copper and copper hydroxide.8 Guava Blight (1 ) Damage symptoms Branch blight is characterized by leaf yellowing and new branches withered in the field. Leaf yellowing is accompanied by defoliation at the late stage of leaf yellowing and leaf defoliation occurs, which is obviously different from blight yellow leaf. The yellow leaves of the disease are mainly caused by iron deficiency and yellowing of the unfolded leaves and new leaves near the tip of the new shoots, and the color is yellowish-white, and the yellow leaves of the branches are relatively bright yellow. In the second year old leaves on the branches, or when the leaves of the old branches become mature, the apex green branches are not susceptible to leaf damage, but once the young shoots are damaged, the leaves and new shoots are withered and browned. (2) Prevention and control methods 1. Strengthen the management of orchards, cut off diseased branches and burn them to reduce the source of bacteria, prevent the spread of diseases, increase fertilizing materials appropriately, make the tree vigor to grow robustly, and increase resistance to diseases. Antifreeze work should be done well to prevent plants from freezing, so as to reduce the incidence of disease, prevent and control pests in time, avoid all kinds of mechanical wounds, and reduce the chance of pathogen infestation.2 In the early stages of the emergence of shoots, a fungicide can be sprayed. Main disease can be scraped off the lesions, and after the wound is sterilized with # $ copper sulfate, a wound protectant is applied.. 3. Guava Blight (1) Symptoms of injury Guava is infected with fruits, branches or seedlings after being infected by the disease. After the infected seedlings are infected, the top sprouts develop a dark green condition, are dull, and then dehydrated. If the seedlings are seriously damaged, the whole plant will fall into leaves and become brown and dark, and only the remaining main branches of the whole plant will remain in the field. The newly emerged shoots of the seedlings are vulnerable to the approach of the ground. The green skin of the affected shoots turns dark brown, and the leaves brown withering. The guava fruit was damaged by the bacteria. The fruit showed water stains and faded. There was a layer of thin mycelium on the surface. After the affected part of the fruit was cut, the internal tissue was not discolored or light brown, and it was easy to distinguish from the white part of the healthy part, but the affected part Vascular changes brown or black, it is very obvious, if long-term stay in the bag or fruit drop on the wet surface, the mycelium of the affected area grows in large numbers, forming a white film covering the diseased parts, and accompanied by acidity. In the process of grafting on the guava nursery, the grafted part was not healed because of the wound, and it was also susceptible to infection, causing the scion to die. Therefore, cleaning up abandoned fruits in the field can reduce the incidence of orchards. The new planting orchard sprays Zn and Mn to exterminate Dalile et al. immediately after it rains, which can quickly suppress the disease. However, field management should be paid attention to on weekdays, such as drainage, orchard planting and other measures. When young shoots of guava sprout and cause wilting, they should be sprayed and cut off to destroy the diseased branches. If there are few newly infected seedlings in the guava nursery, the diseased plants should be removed as soon as possible so as to avoid continuing to indwell the healthy seedlings. In addition to removing the pathogens, the pesticides shall be applied immediately to prevent the spread of pathogens. The guava fruit disease is easy to occur in the early stage. Recently, due to the improvement of production technology, the fruit is imbedded into a plastic bag before being immature, and the frequency of the disease is reduced, but it can still occur under special circumstances. Early guava production, because it was not sequestered by plastic bags, often caused the fruit to be infected in trees. This phenomenon has been greatly reduced in recent years. China Agricultural Network Editor
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