How to control the rice leaf roller? Latest technical method tutorial
The rice leaf roller is one of the major pests in rice-growing regions of China, also known as the rice leaf-rolling caterpillar, the leaf-scraping worm, etc. It is widely distributed across all rice regions. Besides damaging rice, it can also feed on crops such as barley, wheat, sugarcane and foxtail millet, as well as weeds such as barnyardgrass, Leersia hexandra, paspalum, Paspalum distichum, crabgrass, foxtail, goosegrass, thatch grass and reed. Now let us take a look at the control techniques for the rice leaf roller!
Life habits of the rice leaf roller
1. Year-round damage zone: south of the 16°C January average temperature isotherm, including south of the Leizhou Peninsula line. Here, winter food conditions such as ratoon rice and fallen-grain rice exist, allowing it to reproduce all year round with no dormancy.
2. Winter dormancy zone: south of the 7.7°C January average maximum temperature isotherm, that is, from south of 30°C north latitude to the southern coastline of the mainland. It overwinters as larvae or pupae. Among these areas, in Guangdong, Guangxi and southern Fujian, the overwintering survival rate is relatively high. In provinces north of the Nanling Mountains such as Hunan and Jiangxi, although some individuals overwinter in weeds, rice clumps and other places, the overwintering survival rate is extremely low.
3. Winter death zone: north of the 7°C January average maximum temperature isotherm, including Hubei, northern Anhui, Jiangsu, Henan, Shandong and other provinces. No life stage can safely overwinter here.
Agricultural control of the rice leaf roller
1. Select rice varieties resistant to (or tolerant of) the pest, fertilize rationally so that the rice grows robustly, and prevent excessive vigorous growth in the early stage and delayed maturity with lingering greenness in the later stage. Manage water scientifically, appropriately adjust the time of field drying, reduce field humidity during the larval hatching period, or flood deeply for 2-3 days at the pupation peak to kill the pupae.
2. There are as many as 80-plus species of natural enemies of the rice leaf roller, and every life stage has natural enemies that parasitize or prey on it. Protecting and making good use of natural enemy resources can greatly enhance their control effect on the rice leaf roller. There are about 80-plus species of natural enemies of the rice leaf roller, and every life stage has natural enemies that parasitize or prey on it. Egg-stage parasitic natural enemies such as Trichogramma confusum and Trichogramma japonicum, larval-stage ones such as Apanteles cypris, and predatory natural enemies such as spiders and frogs all have a great control effect on the rice leaf roller.
Chemical control of the rice leaf roller
1. The egg hatching peak appears about 7 days after the moth peak, and the 2nd-instar larval peak about 10 days after. It is recommended to apply pesticide 7-10 days after the moth peak. Per mu, use 100 ml of Guangjian or 100 ml of Dafang Awei or 50 ml of Gangtiexia, mixed with 30 kg of water, and spray for control. When new rolled leaf tubes appear, with an average of 30-40 new rolled tubes per hundred clumps, apply pesticide immediately, using the same pesticides as above.
2. Dissect and examine about 20 leaf-rolling caterpillars. If most of the larvae are in the 1st or 2nd instar, per mu use 100 ml of Guangjian or 100 ml of Dafang Awei or 50 ml of Gangtiexia, mixed with 30 kg of water, and spray for control. If the larvae are above the 3rd instar, per mu use 50 ml-75 ml of Gangtiexia and 50 ml-75 ml of Dafang Juanchu, mixed with 45 kg of water, and spray for control.
3. As for the timing of application: if no white streaks have appeared on the leaves in the field and the larvae are young, per mu use 100 ml of Guangjian or 100 ml of Dafang Awei or 50 ml of Gangtiexia, mixed with 30 kg of water, and spray for control. If white leaves have just begun to appear or there are not many white leaves, and the larvae are mainly in the 2nd and 3rd instars, per mu use 50 ml of Gangtiexia and 50 ml of Dafang Juanchu, mixed with 45 kg of water, and spray for control. If a large number of white leaves appear in the field and the leaf tubes begin to dry up, and the leaf-rolling caterpillars are older larvae, per mu use 50-75 ml of Dafang Juanchu, mixed with 45 kg of water, and spray for control.
4. If the larval instars vary, especially when there are many older larvae, per mu use 50-75 ml of Dafang Juanchu, mixed with 45 kg of water, and spray for control; the efficacy is good and the residual effect is long. Note that when controlling the rice leaf roller, a sufficient amount of water must be used, and it is best to use fine-mist spraying.