Some time ago, the Gannan region experienced nearly 20 days of rainy weather, and it was not until June 11 that the first sunny day after the rain was ushered in. Due to the impact of long-term rainfall, the high temperature and high humidity climate that appears after the rain provide favorable conditions for the outbreak of diseases and insect pests, coupled with the weather factors that fail to spray protection in time, etc., so that many orchards of canker disease, brown spot disease, red spider, aphids, leafminer moths, green worms and other diseases and insect pests have erupted to varying degrees.
Recently, the author visited several orchards in Gannan and found that many orchards have psyllids that harm the summer shoots of the navel orange in Gannan. As we all know, citrus psyllids are the only insects infected with citrus yellow dragon disease, and the appearance of psyllids in any orchard is definitely the last thing we want to see, so the prevention and control of citrus psyllids naturally must not be relaxed. If you want to cut down fewer trees in winter, you must control citrus wood lice during the tender shoot period.
Get the right understanding of citrus psyllids
Citrus psyllids belong to the family Psyllididae, which is a citrus Asian psyllid that harms citrus in China. Citrus Asian wood lice in China are distributed in several major citrus producing areas, citrus wood lice is also one of the most important pests in the young shoot stage of citrus, mainly to adult hosts in citrus young shoots to lay eggs, hatched nymphs by sucking the sap of young shoots for survival, until feathering into adults, severely eaten young shoots can appear withered, deformed and so on.
Morphological characteristics of citrus psyllids
Adult wood lice are about 3 mm long, often gray-blue with gray-brown markings, and are covered with white powder. When the leaves stop, the tail will be cocked at a 45° angle to the resting surface. The back of the abdomen is grayish-black, the ventral surface is light green, the top of the head is protruding like scissors, and there are 3 orange-red single eyes, and the compound eyes are dark red. The forewings are translucent with irregular gray-brown markings at the edges, and the hindwings are colorless and transparent.
The female has an orange-red abdomen during pregnancy, a pointed ventral end, a tough laying sheath, and a puncture of the young citrus leaves during egg laying and the stalk of the egg is inserted. The eggs are milky white at first, orange-yellow at first, and orange-red when they hatch. The shape is acquainted with a mango and is about 0.3 mm long. The psyllid nymph is oblate oval, has a total of 5 instar growth periods, is off-white when it first hatches, begins to show its wing buds after 2 years, and is yellow-brown at 3rd instar, often accompanied by white wax filament secretions on the body surface.
Biological habits of citrus psyllids
Under normal circumstances, citrus lice can occur in 11 to 14 generations a year, and the generations in the field overlap. The number of generations that occur in wood lice is related to the number of new shoots of citrus, and the cycle of survival of each generation is related to temperature, generally speaking, wood lice can harm citrus all year round, as long as there are young shoots to smoke wood lice will fly to eat its juice (usually sick wood lice can be infected with yellow dragon disease as long as they eat on the new shoots for more than 5 hours).
Secondly, psyllids generally prefer to harm weak trees, because weak trees usually draw new shoots first than trees with better posture, and the new shoots that are drawn are mostly short and short, which is very suitable for feeding and laying eggs of wood lice. In addition, the number of autumn and late autumn lice occurs most seriously, followed by summer shoots, followed by winter shoots and spring shoots (winter shoots and spring shoots are mainly affected by overwintering lice).
Usually, adult citrus psyllids will be stationary below 8 ° C, when the temperature reaches more than 14 ° C, it can fly and jump, and above 18 ° C can lay eggs and reproduce, the most suitable temperature for pyllids is 25 ~ 35 ° C, if the temperature reaches 42 ° C, the life of citrus psyllids will drop significantly, generally only able to survive for about 2 hours.
Control methods of citrus psyllids
There are many ways to control citrus psyllids, the most common of which include biological control using natural enemies, chemical drug control and physical isolation control.
1. Biological control: Biological control is mainly to reduce the number of citrus psyllids by using their natural enemies to prey or parasitize them. Among them, the parasitic natural enemies of citrus psyllids are mainly bright-bellied glazed wasps and Ali lice jumping wasps, while there are many predatory natural enemies, such as predatory ladybirds and grasshoppers, spiders, ants, praying mantises, etc., and even predatory mites that have a predatory effect on red spiders can also prey on citrus psyllids.
2. Chemical control: Chemical control is mainly through artificial spraying of chemical agents to poison and kill citrus psyllids to achieve the purpose of protecting the tree from its harm. Can be used to control citrus psyllids effective agents there are many, like a lot of permethrin, nicotinoids and some organophosphorus pesticides have a good control effect on citrus psyllids, in the actual use of two different mechanisms of action is recommended compound use together, in order to increase the control effect and help delay the production of drug resistance. In addition, for areas where citrus psyllids occur seriously, when spraying, it is recommended to add egg-killing agents to it, so that a single spray can clean the adults, nymphs and egg blocks together, and the prevention effect is more ideal!
3. Physical isolation prevention: Physical isolation prevention and control is mainly to achieve the purpose of isolating the external wood lice from harming fruit trees by building an insect-proof net for orchards. This method of building insect nets has only become popular in recent years, and is more common in areas with serious outbreaks of yellow dragon disease, but until now there has been no large-scale promotion and use, mainly because the cost of this method is too high, coupled with the short life of insect nets, the general fruit farmers can not accept.
Why is there a year-on-year prevention and treatment of yellow dragon disease?
What is the focus of the control of yellow dragon disease?
1. Planting and purchasing detoxification seedlings: Do not covet small and cheap, do not buy citrus seedlings in the hands of mobile seedling vendors, and should go to regular large nurseries to buy detoxification seedlings.
2. Cut down the diseased trees: For fruit trees infected with Huanglong disease, they should be cut down in a timely manner in accordance with the principle of "spraying first and then cutting down trees" to reduce the source of disease, and timely water glyphosate on the sick tree trees to prevent the resurrection of their long buds.
3. Unified spraying, unified placement: Usually pay attention to erasing the sporadic branches, reduce the food source of the psyllid, and wait until most of the new shoots are about to be pumped out, and then uniformly release the shoots, unified spray protection.
Unified stalking and unified spraying are the top priorities in the prevention and control of citrus psyllids, and the reason why citrus psyllids are not completely controlled and multiplied more and more is because the time of spraying in each orchard is not uniform, and the release of stalks is not uniform.
For example, the orchards of A, B, C, and D are all in the same place, and everyone's orchards are next to each other, if A is spraying today, B, C, and D are planning to spray again after a week, then if there are psyllids in A's orchard, when A is medicated, it will definitely kill some of the psyllids, but at the same time there will definitely be some escaped lice flying to the orchards of B, C, and D to hide in the orchards of B, C, and D, and after a few days, the medicinal smell of A's orchard will dissipate, and there will be lice flying back to continue the harm. When the B, C, and D three people sprayed the medicine, the wood lice escaped the disaster in such a way, repeatedly continuing the vicious circle, and finally leading to the embarrassing situation of "prevention and treatment every year, and every year".