Psyllids are an important pest in the young shoot stage of citrus, and the host young shoots wither and deform the new shoots when they are severely damaged. More importantly, wood lice feed on citrus dragon disease strains, lay eggs and multiply, which can produce a large number of adult fungal wood lice. Adults spread dragon disease by transferring to harmful new plants. Therefore, effective control of the number of citrus lice in orchards can preserve the shoots and inhibit the outbreak of yellow dragon disease in orchards.
1 Morphological characteristics of citrus psyllids
Citrus lice can occur in 8 to 14 generations a year, with overlapping generations.
Wood lice eggs
Mango-like, with a thin apex and blunt rounded ends, with a short stalk, initially spawning
Light yellow, more transparent, later turned orange-yellow. Eggs are mostly laid at the junction of young shoots, young leaves, young shoots and stems, generally polygonal, sometimes can be seen scattered on the leaves of dark orange eggs, mostly necrosis, the growth period of eggs is about 4 days.
The number of eggs laid on a new shoot can range from 100 to 200 grains. A female adult produces at least about 120 eggs and up to about 1150 eggs, with an average of about 500 eggs.
Wood lice nymphs
a to f are wood lice eggs to 5-year-old nymphs in order (stereo mirror magnified 50 times)
Nymphs are divided into five instars, and with age, their body size increases significantly. The first instar nymph is flattened and oval, has 2 red compound eyes, no wings, one eye is not visible, and the growth period is about 1 day; the second instar nymph is enlarged, and the wing buds appear in the second segment of the thorax, and the growth period is about 2 days.
The wing buds of the third-instar nymph are significantly enlarged, the leading edge extends to the posterior edge of the compound eye, the posterior margin reaches the 3rd segment of the abdomen, the antennae end become black, and a single eye appears, and the tail whisker appears, and the growth period is about 3 days.
The body color of the fourth-instar nymphs becomes darker, the compound eyes become larger, the leading edge of the wing buds exceeds the compound eye, the posterior edge exceeds the 3rd segment of the abdomen, the anterior and posterior wings are misaligned, the antennae become blacker, the tail whiskers are increased, and the growth period is about 3 days.
Fifth-instar nymphs have a dark body color, clear texture, all the antennae except for the basal nodes are blackened, there are 2 clear bristles at the ends, and the tail whiskers continue to grow and lengthen, and the growth period is about 5 days.
Adult wood lice
Female citrus wood lice
Citrus wood lice male
Psyllids are small insects, oviparous in both sexes, with little difference in size between males and females, two pairs of wings, leathery forewings, brown markings, hindwing membranous and transparent;
The female has an orange-red abdomen, a pointed ventral end, a tough spawning sheath during the egg-laying period, and punctures the citrus buds or young leaves during egg laying, and inserts the egg stalk. Egg-laying females live about 40 days. However, parthenogenes of citrus psyllids do not lay eggs and can live for more than 156 days, with males living up to 98 days.
2 Citrus psyllids life habits and harm
Adults do not like to move, the tail is cocked, the insect body and the leaves at a 45 ° angle, a little literary! Mostly docked on the back of the leaf or on the stem for feeding, the larvae increase their mobility with age, but generally do not move when unobtrused.
Adult insects before eating body swing left and right a few times is conducive to the needle into the tree body, take the sap, find the feeding position after generally do not change the feeding position, all day long to eat, typical foodie! The eaten leaves may appear yellowish and distorted.
Nymphs gather on the young shoots of the plant to feed on the hazards, and as the insects grow in age, they continue to move to the lower part of the young shoots of the plant, and a large amount of white waxy honeydew is discharged from the tail, and the young shoots are often withered.
The pathogens of soot can use white waxy honeydew as a source of nutrition, and orange groves that shade damp and poor management are susceptible to disease.
3 Occurrence rules and toxicity characteristics of citrus psyllids
Regularity of occurrence
🔹 The number of generations in a year is related to the number of new shoots in citrus, and the length of each generation is related to temperature.
🔹The overwintering generation begins to lay eggs in late March, hatches in mid-to-late April, and adults begin to appear in early May. The nymph infestation occurs from April to September. Autumn is the peak of nymphs and adults.
🔹 Summer shoots are the most affected, followed by autumn shoots, especially early summer shoots in May, which may cause yellow dragon disease after being killed. Spring shoots, on the other hand, are mainly victimized by the overwintering age.
🔹From mid-October to early November, there is often a late autumn shoot, and the wood lice will have a peak and overwinter with contemporary adults.
Transmission characteristics of high frequency of disease transmission: pyllids and nymphs can transmit diseases, and 80% of individual lice can transmit yellow dragon disease bacteria to healthy trees.
Fast transmission of poison: 5 hours can transmit poison by eating the young leaves of diseased trees.
Close diffusion distance: Adults have limited flight ability and spread with the wind.
Lifelong transmission of poisonous diseases: Psyllids feed on the young leaves of diseased trees to allow pathogens to enter and proliferate in insects, and then the fungus lice transmits the poisonous bacteria to healthy plants by transferring plants to suck. Once the psyllid is sick, it can pass on the poison for life.
4Countyllid control experience sharing
Prevention and control of misunderstandings
First, because citrus psyllids are present, but there must be psyllids in the shoot stage, so the control is not seasonal, but annual.
Second, the control of pyllids is not a matter for one farmer, one orchard, or one fruit farm, but for all growers, all orchards, and fruit farms. It is necessary to achieve unified defense and rule.
Prevention and control method Winter Clearance: This is the key to the key to prevention and control throughout the year. At this time, the adult insects are inactive in the case of low temperatures, using organophosphorus agents or mineral oil spraying, as long as they can be sprayed evenly and contact with the insect body, the effect is very good.
Spring shoot stage: before germination, kill the overwintering lice and reduce the population base.
Summer stage: during the critical period of control of wood lice, it is necessary to spray medicine to control wood lice when the summer leaves are withdrawn. The loophole in the prevention and control of wood lice lies in the treatment of summer shoots, and the varieties or orchards that do not erase summer shoots, such as sugar oranges, often only pay attention to the control of summer shoots, most of them take the method of controlling the stems, and the retained summer shoots do not pay attention to the prevention and control of wood lice, and the spread of yellow dragon disease accelerates.
Autumn shoots: Before uniformly pruning the summer shoots and putting them in the autumn shoots, spray the agent to kill the psyllids; when the autumn shoots germinate, they combine the control of citrus aphids and leafminer moths, spray drugs to control the psyllids and protect the autumn shoots.
Winter shoots: Orchards with winter shoots or late autumn shoots should still pay attention to prevention and control.
Commonly used agents are mainly organophosphorus, generally 50% octyl thiophosphate emulsion or 48% chlorpyrifos emulsion 1000 ~ 1200 times liquid, combined with the control of leafminer moths and aphids in the summer stage, can be sprayed with avermectin + octyl thion, a drug is multi-effective.
Precautions
🔹 Before cutting down the diseased tree, the whole park must spray to kill adult psyllids and nymphs to avoid the spread of poison from poisonous pyllids.
🔹 Strengthen the management of fertilizer and water, so that the citrus trees grow strongly, and the hair tips of each new shoot are neat, which is conducive to spraying drugs to control psychics at a uniform time.
🔹 The soil of the orange garden is mostly acidic, and sea spirit humic acid plus compound fertilizer can be applied to regulate the soil, improve the rhizosphere environment, balance nutrition, and tidy hair.
🔹 One shot and three medicines, unified prevention and treatment. The first spray time should be carried out during the dew bud stage (bud length less than 1 cm).
🔹 Other host plants that still exist in the orangery should also be sprayed and cut down to prevent parasitism.
(Source: Agricultural Assistant (ID: nyzs360), copyright belongs to the original author)
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