(1) Main diseases
At present, no diseases that have a significant impact on yield have been found. Usually seedling diseases include root rot, stem rot, dry blight, etc. However, as long as the cultivation and management measures are appropriate, such as reasonable fertilization, improving drainage conditions, preventing low temperature and cold damage in winter and spring, and high temperature burns in summer and autumn, the occurrence of these diseases can be reduced. Diseases on mature trees include gummosis, root rot, etc. The causes are unknown, but attention should be paid to them.
(2) Main pests
More than 40 species of cashew pests have been found in Hainan Island, which damage stems, branches, leaves, young shoots, flowers, fruits and other parts. Among them, the coffee-breasted beetle, the tea bug, and the fruit borer pose a great threat to cashew production and are the most important cashew pests in Hainan.
1. Plocaederus obesus Gahan.
Also known as coffee beetle, it harms the trunk and taproot of cashew nuts. Adults usually lay eggs in cracks in the bark of stems within 1 meter from the ground. After hatching, the larvae drill into the trunk and feed, causing glue to ooze and insect feces to be discharged from the damaged areas. In the later stages of the disease, the leaves turn yellow and fall off, the bark cracks and peels off, the branches dry up, and in severe cases, the plant dies.
Prevention
In orchards where low-yielding trees have been replaced with high crown replacements, the damage rate of coffee beetles has increased alarmingly. In order to reduce the damage caused by beetles, the intercepted trunks should be painted with lime water when cutting, and asphalt or cow dung slurry mixed with insecticide powder should be applied to the cutting edge.
2. Helopeltis fasciaticollis Poppius
Also known as the tea bug, adults and nymphs suck the juice from twigs, leaves, flower branches and developing pears and nuts. . Affected young leaves and blades will dry up, damaged young fruits will appear spots, and finally wither and fall off. Damage to the inflorescence will lead to inflorescence blight. In the season of major occurrence, the damage rate of inflorescences and young shoots can reach 30-60%, and the highest is more than 90%. Failure to prevent and control in time often results in harvest loss. In Hainan Province, the tea bug has 12 generations per year, with overlapping generations.
Prevention and Control
Regular investigation of the occurrence of Lygus bugs in orchards from October to December every year is the key to prevention and control work. After November to December, Lygus bugs begin to reproduce at an accelerated pace. It is necessary to fully understand the situation of the central insect strain and spray pesticides to eliminate the insects in a timely manner. 10 days after the first spraying, it is best to spray the protozoal strain again. In the future, the development of the insect situation still needs to be closely monitored. Once a new insect strain is discovered, it should be controlled immediately. Effective agents include 2000-fold solution of 20-fold dimethoate and 1200-fold solution of Dimethoate mixture (40 dimethoate and 80 dichlorvos), both of which have good effects. Measures such as pruning and thinning are also beneficial to the prevention and control of blind stink bugs.
3. Fruit borer (Nephopteryx sp.)
Dangers pears, nuts, inflorescences and young shoots. The accumulation of insect feces on the affected area is a prominent feature of fruit borer damage. The larvae mostly feed from the joint between pears and nuts, causing the fruit to become hollow.
Prevention
The appropriate period for chemical control is usually in mid-to-late March for the first spray. 20-speed insecticide or 2.5 insecticide-killing solution 2000 times, 40 omethoate or 25 insecticide-killing 1000 times solution are all effective.