Cnaphalocrocis medinalis, Latin name Cnaphalocrocis medinalis Guenee, also known as the green scraping bug, adult length of 7 to 9 mm, yellowish brown, brown forewings with two lines, two lines of 1 short-term, outer edge having dark brown band; hind wing with two lines, the outer edge is broadband; male forewing front central with a flash, hollow " starting point ", the female moth wing had no " starting point ". Eggs about l mm, flat and oval, slightly raised, primiparous white transparent, near hatch when flaxen, parasitized eggs as black. Mature larvae of length 14 ~ 19 mm, young larvae turn green, yellow green, orange and red mature larvae. Pupal length 7 ~ 10 mm, beginning after the turn yellow, brown, long cylindrical.
Rice leaf roller is a migratory pests, from north to south, year produce 1～ 11 generations; Nanling Mountains south of a line, all the year round a certain number of pupae and a small amount of overwintering larvae, 30 degrees north latitude in winter the majority cannot, in the initial insect source from the South moved to. Adult phototaxis, perched hasten concealment and spawning twigs, moderate temperature and high humidity oviposition amount is large, generally each female lays 40 to 70 eggs per unit area yield of grain; many, also has 2～ 5 grains produced in together, the temperature of 22 ～ 28~C, relative humidity above 80%, egg hatching rate of up to 80 to 90% above. The newly hatched larvae bore into the leaves into the most damage, after age 2, the leaf node bracts, booting stage can be drilled into the ear bud feeding. Larval life fresh leaves of 5～ 6, up to 9～ 10, intake with instar increases, 1 ～3 instars eat leaves only in 10%, mature larvae of most leave Laochong bracts, in rice leaves and invalid plexus base cent evil leaves on the tree full of cocoon for pupation. Rice Leaffolder occurrence degree and closely related to climate, moderate temperature and high humidity conditions, favorable oviposition, hatching and larval survival, therefore, rainy day and dew and humid weather, is conducive to the rampant occurrence.
Newly hatched larvae feeding on the leaves, appear needles point, also the first in the inside of the sheath damage, along with increased instar, spinning up on both sides of the leaf margin of rice leaf blade, longitudinal rolls into cylindrical worm bracts, larvae hide within defoliation mesophyll, leaving skin was white stripe. When severe " bug bud clusters, white leaf man-tin ". In pregnancy, heading date suffer losses.
Recommended prevention methods: on the basis of rice tillering and earing stage susceptible to rice leaf roller, especially during spike loses more characteristics, chemical control strategy, should strictly control during spike of victimization, not relax at tillering stage of severe damage on behalf of other principles. Recommended dosage: in hatching peak after 1 ~ 3 days after 667m2, each with 10000000000 spores /ml Empedobacter brevis suspension agent of 80 to 100 45 kg water spray mist, insecticidal effect in more than 90%. Plant field should maintain 5 ~ 7 cm layer, medicine is maintained after layer 3 ~ 5 days.
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