According to the expert meeting of the Guangdong Provincial Crop Disease and Pest Occurrence Trend, combined with the comprehensive analysis of factors such as the source base of diseases and insects, crop layout, cultivation management and climatic characteristics, it is predicted that the overall incidence of crop diseases and insect pests in the province in the second half of the year is more important, and the occurrence characteristics: insect pests are heavier than diseases; the occurrence of rice "two migrations" pests (rice planthopper and rice longitudinal curl leaf borer) is widespread; and the potential risk of epidemic diseases is relatively large.
Prediction of crop diseases and insect pests in Guangdong Province in the second half of 2017
Among the pests of rice "two migrations", rice longitudinal leaf borer is partially concentrated in Guangzhou, Shaoguan, Yangjiang, Zhanjiang, Maoming and other cities. According to the expert consultation and prediction, its occurrence area is 18 million mu and cannot be ignored.
Prediction of the occurrence trend of rice longitudinal leaf borer in the second half of 2017 in Guangdong Province
Of course, the rice longitudinal leaf borer is not only harmful in Guangdong, but also widely distributed in all rice areas in the country. Let's take a closer look at the rice longitudinal leaf borer, and introduce the hazard characteristics and control strategies of this pest for the reference of the majority of farmers.
Rice longitudinal curl leaf borer of various periods
Rice longitudinal leaf borer, also known as scraper, white leaf worm, bract leaf worm, etc., is a typical migratory pest, and is also one of the main pests in China's rice producing areas. Improper control will affect the ear extraction of rice, reduce the weight of 1,000 grains of rice, increase the dry grain, and seriously affect rice yield.
First, the occurrence of rice longitudinal curl leaf borer
Rice longitudinal leaf borer subcontracting hazard process
Rice longitudinal leaf borers cannot overwinter north of 30° north latitude, and neither larvae, adults, eggs nor pupae can survive at latitudes above 30°, so they are a long-distance migratory pest.
Rice longitudinal leaf borer can occur in 1-11 generations a year, and the further south the geographical location, the more generations occur. Every spring and summer, adult insects migrate from south to north with the monsoon, and land with temperature and rain, becoming a source of insects in non-overwintering areas. In autumn, it breeds southward with the monsoon and overwinters.
Second, life habits
1. Eggs
In order to facilitate egg laying, and in order for the larvae to have a good source of nutrients after hatching, adults have a preference for egg laying. (Pictured is the white insect eggs of rice longitudinal curl leaf borer on the leaf)
During the tillering phase, adults lay their eggs on the second and third young leaves; during the gestational and panicle extraction stages, adults lay their eggs on the heart and second young leaves.
2. Larvae
Rice is in different stages, and the site of incubating larvae of rice longitudinal leaf borer is slightly different. (Pictured is 2-year-old (top) and 4-year(bottom) rice longitudinal leaf borer larvae)
(1) Tillering stage: Because rice seedlings are small and tender, most larvae will crawl into the heart leaf or nearby leaf sheath after hatching to nibble on the leaf flesh.
(2) Panicle extraction and pregnancy panicle stage: rice leaves are old and healthy, and most of the larvae will be on the inside of the sheath of young leaves or crawl into the old buds. At the end of the gestational panicle, even the young chaff is eaten.
Popular Science Link: Larval Age Distinction
Rice longitudinal curl leaf borer 1-5 instar larvae and corresponding leaf hazards
One-year larvae
2-3 days after the peak period of the moth, when the rice is in the tillering stage, carefully check the heart leaf and the sheath of the young leaf of the rice plant, if you find a needle-sized, translucent small white dot, and no buds, careful search will find 2-3 social head black carbine white larvae, it is a first-class larva.
Second-instar larvae
In the blue-green rice leaf or 3-5 cm from the tip of the leaf, there is a bunch of folded small insect buds, the buds are 2 to 4.5 cm long, the buds are fresh, shiny, tear open the buds, there is a larva, frightened and drooping, the leaves have obvious white stripes of different lengths, and pale green, relatively moist, with coarse powdery insect droppings, which are infested by second-instar larvae.
Three-year-old larvae
The large leaves are made into longitudinal stripe buds of 13 to 16 cm long, which are wound by transparent worm filaments, and the openings at both ends of the buds have longitudinal white stripes that are equal to the leaf veins, and there are more moist feces, and there is a larvae in the buds, which is infested by the third-instar larvae.
Fourth and fifth instar larvae
The harmful insect buds are slightly longer than the third instar, most of the green parts in the buds are eaten, the parts that are eaten are whitish, the leaves above the whitish part are dehydrated and dried, and the insect droppings are dried up or powdered. Bugs could not be found in the buds, and most of the bugs had already switched positions.
3. Pupae
During tillering to gestational panicles, the larvae mostly pupate on the young or yellow leaves at the base of the rice bush, and after the gestational panicle, the larva pupates on the inside of the dead leaf sheath. (Pictured is rice longitudinal leaf borer pupae)
4. Adults
Pupae generally feather into adults at night, and adults have a strong habit of shading and sheltering. (Pictured is adult rice longitudinal leaf borer)
Adults are diurnal and nocturnal and phototropic. During the day, some adult insects hide in dense, shady, humid rice fields; Others migrate to lush pastoral or overgrown areas nearby, and at night fly to tender green rice paddies to lay their eggs. The spawning site is mostly in the middle of the plant and the back of the upper leaves, especially the 3 leaves are the most.
3. Symptoms of harm
Rice longitudinal curly leaf borer rice field hazards
The rice longitudinal leaf borer is infested by the tip of the larvae spitting silk curl leaves. Hatching larvae - generally crawl into the heart leaf of rice or nearby leaf sheath, the 2nd instar began to spit silk longitudinally into small insect buds at the tip of the leaf, and after 3 years began to turn into a pest, the 4-5th age food volume increased sharply, and its leaf consumption accounted for more than 90% of the total larval food.
When the larvae are infested, they hide in the bracts to feed on the epidermis and green mesodermal tissue, forming white stripes, and the heavily affected fields are white, which seriously affects rice yield. The loss is greatest at the gestational and panicle extraction stages.
Adults emerge diurnally and nocturnally, have phototropism, and prefer to spawn in paddy fields where the growth of tender green is in the round stalk jointing stage and the young panicle differentiation stage. The spawning site is mostly in the middle of the plant and the back of the upper leaves, especially the 3 leaves are the most.
Fourth, prevention and control methods
Pesticides are applied to control pests
1
Strengthen field management
Strengthen fertilizer and water management, apply sufficient base fertilizer, and apply topdressing early to make rice grow robustly and neatly; so that the early stage is not long, and the later stage is not greedy, so as to improve the insect resistance of rice and shorten the period of pest. Timely irrigation in the field, timely drying of the field, application of nitrogen fertilizer in an appropriate amount and in time, or irrigation of deep water for 2 to 3 days during the peak period of pupal pupae to kill the pupae;
2
Timely medication
First of all, we must grasp the optimal prevention and control period. It was timely controlled when there were more than 15 new buds of two or three instar larvae per 100 stings from the tillering stage of rice tillering to the panicle extraction stage.
Second, choose the appropriate agent. According to pest and disease intelligence, 40% chlorine worms per acre are available 1-2 days after the peak of egg incubation. Thiamethoxine water dispersible granules 10 g, or 20% chlorcloprosperm benzamide 10 ml; or 10% tetrachloroproxamide suspension 30-40 ml; or 33% avyl. 40-50 grams of hydrazine wettable powder or 2.2% methylaminoavermectin microemulsion 2000 times, add 30-45 kg of water to a fine spray. Timeless plots can be supplemented with 12 ml of 15% indicosus suspension. When the amount of insects is large or the generation overlap is serious, and the pest of rice longitudinal leaf borer cannot be effectively controlled at one time, the drug is re-administered after 5-7 days. (Note: The above pesticide dosage is for reference only, please strictly follow the product instructions in different regions to apply)
The longitudinal leaf borer is a leaf pest, and it should be better to mist or fine spray. The application time is generally good in the morning and evening. In case of rainy weather, the rain must stop and grasp the medication, and cannot be delayed.
3
Biocontrol
There are more than 80 kinds of natural enemies of rice longitudinal leaf borer in China, and there are natural enemies parasitizing or preying at each insect stage, and the protection and utilization of natural enemy resources can greatly improve the control effect of natural enemies against rice longitudinal leaf borer. Parasitic natural enemies at the ovoid stage, such as pseudo-Australian red-eyed bees, rice borer red-eyed bees, larval stages such as longitudinal leaf borer cocoon bees, predatory predators such as spiders, frogs, etc., have a great control effect on the longitudinal leaf borer. Advocate physical and ecological prevention and control technologies such as duck farming and fish farming in rice fields.
4
Physical control
Adult rice longitudinal leaf borer has phototropism, and qualified farmers can install frequency vibration insecticidal lamps to trap adult insects, which can effectively reduce the source of next generation insects; in addition, adult insects can be trapped by sexual attractants to control rice longitudinal leaf borer, which is safe, green and environmentally friendly.
Source: China Agricultural Extension Network, Hubei Agricultural News, Agricultural Finance Network Seed Industry Treasure Book