(1) Ralstonia solanacearum: Ralstonia solanacearum infects young trees in the forest, and its aerial manifestations can be divided into two types. The first is acute, in which the leaves of diseased plants wilted due to rapid dehydration, and the leaves hung on the branches and did not fall off, showing typical symptoms of bacterial wilt. The time from the onset to the death of the whole plant is very short, usually only 2-3 weeks. The second type is chronic, the diseased plant is stunted and short, the lower leaves first turn purple, then gradually deepen and develop upwards, and finally the leaves dry and fall off. Irregular dark brown necrotic spots appeared on some stems and lateral branches, and the whole plant died in severe cases. It takes a long time from the onset to the death of the whole plant, usually 3-6 months. Bacterial wilt of eucalyptus is common in high temperature and high humidity. Root neck injury, surface runoff and rooting among plants are the main ways of pathogen invasion and transmission. Control measures: select disease-resistant strains; Do a good job in the quarantine of nursery seedlings and try to avoid going up the mountain with illness; Moreover, try not to build eucalyptus forests on woodlands (soil where peanuts, tobacco, potatoes, tomatoes, mulberry trees, kapok, Casuarina equisetifolia and canna are planted) that are easy to carry Ralstonia solanacearum; Do not apply immature organic fertilizer; Strengthen tending management and improve the disease resistance of forest trees. There is no exact and effective prevention and control method after the onset. Once found, it can only be uprooted immediately, and the soil in the plant hole can be disinfected with lime to eliminate the diseased plants.
(2) scorch disease (commonly known as defoliation): This disease is caused by high temperature and high humidity, which can cause eucalyptus to die in severe cases, especially when eucalyptus urophylla and its clones encounter high temperature and rainy weather for six or seven consecutive days, and some places with low terrain, poor drainage, high afforestation density and poor forest permeability are prone to disease. Prevention and control measures: Choose land with good drainage for afforestation, and make drainage ditches in low-lying areas. The planting density should be appropriate, not too dense.
(3) Stem rot of eucalyptus seedlings: it is a disease of eucalyptus seedlings. When it happens, the stems of eucalyptus seedlings rot and die gradually. Control measures: chlorothalonil or chlorothalonil or Bordeaux solution should be used at seedling stage or before seedlings leave the nursery, and then sprayed after diluted to the concentration.
(4) Eucalyptus leaf roller moth: it harms young leaves of Eucalyptus from April to August every year, damages young branches and terminal buds, makes young trees wither and affects growth. Control measures: (1) Manual kneading. When you see the tender leaves of a small tree with curly leaves, crush the larvae in the curly leaves with your hands. (2) Pesticide spraying. Spray with trichlorfon 600 times solution and a small amount of kerosene or dimethoate 1000 times solution or pyrethroid (according to the concentration).
(5) Termites: mainly harm the bark of eucalyptus trunk and seriously affect the growth of trees. Prevention and control measures: (1) trapping and killing. Bury with bagasse, sugar, etc. Lure termites to concentrate and then poison them with pesticides; (2) Drug-driven. Metarhizium anisopliae produced by Guangdong Academy of Forestry has a good effect. The use method is to prepare Metarhizium anisopliae into liquid medicine according to the instructions, soak the afforestation seedlings in the liquid medicine, and then take off the afforestation, which can effectively control termites; (3) Internal inhalation poisoning. Applying carbofuran to the soil around small trees will poison termites. Carbofuran can be applied alone or together with other base fertilizers.
(6) Scarab: Larvae (commonly known as chicken mite) harms the roots of young trees, especially some cultivated land such as sugarcane fields and sweet potato fields, with many larvae and serious harm. Adults harm the leaves of young trees. Prevention and control measures: (1) During afforestation, 4-5 kg of trichlorfon powder (or 2.5 kg of terbutyphosphine) should be evenly scattered in planting holes to drive away and kill turtle larvae. (2) The pesticides trichlorfon and methamidophos are diluted into 600-800 times solution and sprayed on the leaves, which can effectively kill adults.