Citrus psyllids belong to the family Psychiciaceae, which is a citrus Asian psyllid that harms citrus in China. Citrus Asian psyllids are mainly distributed in Guangdong, Guangxi, Jiangxi, Hunan, Sichuan, Chongqing, Hubei, Zhejiang and Fujian and other major citrus producing areas. Wood lice mainly harms rue family plants, but citrus is the most affected, followed by yellow peel, wolfberry and jiuli incense. Citrus psyllids are one of the most important pests in the young shoot stage of citrus, adults often host to lay eggs on the young stems of citrus, and hatched nymphs suck up the sap of the young shoots until they become adult feathers. Severely affected young shoots can show symptoms such as withering and distortion, and the white honeydew-like excrement secreted by the psyllids will adhere to the new shoots, thus inducing soot disease, hindering the photosynthesis of the new shoots and seriously affecting the normal growth of the new shoots. More importantly, as the only vector of pests that can transmit yellow dragon disease, the wood lice (sick wood lice) can infect healthy citrus trees with yellow dragon disease as long as they are smoked on new shoots for more than 5 hours. (This means that even if you kill the psyllids with a spray on the back, the citrus trees that are smoked will still be infected with yellow dragon disease.) ）
Morphological characteristics of the psyllid
Under normal circumstances, the lice can occur in 11 to 14 generations a year, and the generations in the field overlap. 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 psyllids
The number of generations that occur in psyllids is related to the number of new shoots in citrus, while the cycle of survival of each generation is related to temperature. Generally speaking, wood lice can be harmful all year round, as long as the citrus has young shoots to smoke wood lice will fly to eat the sap of young shoots, and wood lice prefer to harm weak trees, because weak trees generally draw new shoots first, and the new shoots are mostly short and short, which is very suitable for wood lice to eat and spawn. In another year, the mid-autumn and late autumn shoots are the most harmful, because this time is the time when the number of wood lice is the largest, followed by summer shoots, followed by spring shoots (spring shoots and winter shoots are generally mainly affected by overwintering wood lice)
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Adult wood lice will be stationary below 8 ° C, above 14 ° C can fly and jump, at 18 ° C can lay eggs and breed, the most suitable temperature for wood lice is 25 ° C ~ 35 ° C, when the temperature is as high as 42 ° C, the life of the wood lice will be greatly reduced, generally only able to survive for 2 hours.
How to control psyllids
The things that exist in nature all pay attention to the law of mutual resistance, one thing descends one thing, and the same citrus wood lice also has natural enemies that can subdue it. Therefore, the general control methods of citrus psyllids are mainly divided into biological control and chemical control, let's first talk about the biological control methods of citrus psyllids.
Biological control of citrus psyllids can usually use its natural enemies to inhibit its reproduction, and the main natural enemies of citrus psyllids are parasitic natural enemies and predatory predators. Among them, the parasitic natural enemies are mainly bright-bellied glazed wasps and Ali lice jumping wasps, especially bright-bellied glazed wasps, which can not only parasitize nymphs of all ages of citrus psyllids, but also female bees can also feed on young citrus psyllid nymphs. According to statistics, a bright-bellied glazed wasp can kill more than 500 pyllid nymphs in a lifetime, and the parasitic rate of individual parasitic bees to pyllids can even reach more than 80%! The Ali lice jumping wasp mainly parasitizes citrus 4 to 5 year old pyllid nymphs, and the Ali lice jumping wasp can also reproduce parthenogenetically, and it can also parasitize about 300 pyllid nymphs in its lifetime.
Bright-bellied glazed bee diagram (top) Ali lice jumping bee diagram (bottom)
After introducing the parasitic natural enemies of the psyllid, let's talk about the predatory predators of the citrus psyllid. There are many predatory predators of citrus wood lice, including 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 wood lice. The natural hostilities that exist in nature play an extremely important role in inhibiting the reproduction of citrus wood lice!
The advantage of these biological controls is that they are pollution-free and do not require any cost. However, if you want to use the beneficial insects that exist in nature to help control insect pests, you must protect the ecological environment of the orchard, and at the same time, you must pay attention to the use of drugs that are harmful to natural enemies, otherwise you will invisibly help the psyllids. Of course, biological control is definitely lower than chemical control, so for the orchard has occurred a large number of pyllids we need to use the help of chemical agents to achieve accurate and efficient control purposes.
Predatory gourd
green lacewing
Predatory mites
There are many main agents for the control of citrus psyllids, such as the commonly used control of adult insects are permethrins and organophosphorus and nicotine pesticides, it is recommended to use more compounds of these ingredients to improve the efficacy such as chloryanide chlorpyrifos, kung fu thiamethoxazine, kung fu thiamethoxam, kung fu pyrethialine, thiamethoxine, thiamethoxazine, triazole, pyrazone, fu propranolamine, etc. Pay attention to the rotation of the use of agents to delay the production of resistance, in addition to the adult lice, the control of nymphs and eggs can not be neglected, many fruit farmers do not control the psyllids is because they only pay attention to the control of their adults and the psyllid nymphs and eggs have never chosen special agents to spray. For citrus psyllid nymphs and eggs, the control effect is good, there are spirant ethyl ester and pyraprofen, when taking drugs, try to add the drug to control adult nymphs and eggs together, so that you can realize that the ancestors of the psyllids can be eliminated for eighteen generations with a single medication. The most important point is that when using drugs, we must choose the products of regular large manufacturers, so as to ensure the safety and effect of the use of drugs, many of the same ingredients produced by different manufacturers The reason why the price is uneven is because the original drugs and auxiliaries used by each manufacturer and the formula and the production process are not the same, so the cost of production is not the same, of course, the final use effect and safety are not the same. Just like the inorganic copper preparation produced by some imported manufacturers, due to its special process, the safety is much higher than that of conventional varieties, so even if some other agents are mixed or even some good quality foliar fertilizers, there will be no drug damage, and the general domestic manufacturers do not have such technology, so the product price is relatively low.
With the large number of lice and harm in recent years, more and more citrus producing areas have been trapped by yellow dragon disease, and many areas have even reached the phenomenon of destroying other fruit trees of this species. In addition to the two methods mentioned above, some growers now choose to build insect control nets to physically isolate psyllids. This method has played a very good role in isolating and preventing the harm of psyllids, but due to the high cost and the short service life of the insect control net, the method has not been chosen by many people, of course, the relatively low cost of the method of establishing an orchard windbreak also has a certain effect on isolating citrus lice. The key to the prevention and control of citrus psyllids is to spray frequently until the young shoots are fully mature in the new shoot stage, and unified application is the key, and the reason why citrus psyllids are difficult to control is because our usual spraying time is not uniform. For example, if Zhang San, Li Si and Wang Mazi's orchards are next to each other in the same place, and today only Zhang San is taking medicine, if there are wood lice in Zhang San's orchard at this time, then some of the wood lice may be killed when Zhang San is spraying, but at the same time some wood lice will fly to Li Si and Wang Mazi's orchard to take refuge, and when the medicinal smell of Zhang San's orchard is gone, it will fly back again, and year after year, the orchards of the three people will be seriously endangered by the wood lice. And if the three of them applied the medicine uniformly every time, then the lice would have nowhere to hide or the probability of appearing would be much lower, and the control of the lice would be able to achieve good prevention effects year after year.
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