Commonly known as thrips, the tauroptera insects are known to about 6,000 species worldwide and about 600 species in China. The larvae are white, yellow, or orange, and adults are yellow, brown, or black; they are tiny, 0.5–2 mm long and rarely exceed 7 mm. Widely distributed all over the world, the diet is complex, mainly plant-eating, fungal-eating and predatory, of which plant-eating accounts for more than half, is an important economic pest.
Adults and nymphs of thrips mostly feed on the back of young leaves and flowers, and file the epidermal tissue with a file suction mouthpart to suck the juice of young leaves and flowers, and the young leaves and young branches that are killed become hard and curled with scars, and the young fruits will harden and produce scars after being damaged, which will cause fruit drops when serious, which seriously affects the yield and quality, and some species can form galls. In addition, smoked thrips and western flower thrips can spread the virus, bringing serious economic losses to agricultural production. There are also some thrips species that are beneficial to humans, with tower six-point thrips preying on leaf mites and their eggs, and horned flower-toothed thrips can help plants spread pollen.
Citrus leaves in the nursery
Thrips feed on citrus flowers
Thrips host a wide range of occurrences throughout the year, peaking in March to May and September to November. Female adults mainly reproduce parthenogenetically, occasionally of both sexes, and it is extremely difficult to see males. The eggs are scattered in the mesophyll tissue, and each female adult lays 22 to 35 eggs. Female adults live from 8 to 10 days. The egg stage is 6 to 7 days from May to June. Nymphs feed on the back of the leaf until the end of advanced age, and fall into the pupae of the topsoil.
Thrips like warm, arid weather, its suitable temperature is 23 ° C ~ 28 ° C, suitable air humidity of 40% ~ 70%; too high humidity can not survive, when the humidity reaches 100%, the temperature reaches 31 ° C, all nymphs die. After heavy rain or watering, the soil compacts, so that nymphs cannot enter the soil to pupate and pupae cannot hatch into adults.
On June 4, 2020, on the 12# citrus tree in the No. 2 net shed, a relatively rare red thrips population was found, about 400-500 nymphs, bright red in body color, 2-3 mm in length, tail cocked, crawling faster, tail swinging left and right when crawling, mostly gathered in branches, dead branches healing, rough bark or cracked bark, bark grow mold, of which 2 are larger, about 5 mm in length, in addition to 7 black thrips with a body length of about 5 mm in the red thrips population, Red thrips and black thrips get along peacefully. This citrus tree was transplanted on April 27, 2020, germinated earlier, the bud leaves of the lower branches were ripe, some branches had flowered, and the red thrips population occurred on the taller branches on the left, with anthrax on the upper shoots, but no thrips.
Newly transplanted 12# citrus tree
A population of red thrips that congregate
On June 8, 2020, another inspection found that the red thrips population had expanded to 7 large branches of the whole tree, and there were smaller red thrips nymphs in the population, and there were still several black thrips active in the red thrips population, and it was estimated that there were nearly 1,000 red thrips in the whole tree. Check that the young leaves and young branches are free of thrips, and the mold on the branches is obviously more. Check the neighboring citrus trees for no red thrips.
The number of herds exploded to nearly 1,000
On June 9, 2020, 10 red thrips appeared on the 1 branch of the 7# tree next to it, and 8 red thrips appeared on the 1 branch of the 16# tree, but none of them were found on the young leaves.
On June 15, 2020, the small red thrips nymphs seen on the 8th have grown, most of them are 2-5 mm long, and the population number is significantly reduced compared to what was seen on the 8th, while the number of black thrips has increased to more than 10, and the red thrips of the 7# tree next to it have become fewer, carefully observe some of the hidden cracks, and several red thrips of the 16# tree can not be found.
Red thrips population
Saprophytic bacteria produce a large number of fruiting bodies
Hide in cracks
On June 18, 2020, the population of red thrips dropped sharply, about 300 or so, and different sizes of red thrips could be seen, while the black thrips increased to 66, and 17 red thrips were found in the 7# tree next to it, and 1 was found in the 16# tree.
Red thrips and black thrips
Populations have plummeted
Red thrips for macro shots
This red thrips population has not been found to be harmful to citrus leaves for the time being, is it bacteriophagic? From June 4, 2020 to June 18, 2020, the number of red thrips has suddenly increased and decreased in the number of red thrips, is it the nymph that quickly grows to the end of the advanced age to stop feeding and fall into the topsoil pupae? Or is it affected by the high temperature and humidity in the net shed that affects the growth of the red thrips population? etc. needs to continue to be observed.