Rice seedlings turning yellow, leaves curling, leaf-rolling: what to do? A detailed guide to prevention and control

There are many causes of the rice leaf-rolling phenomenon, and the most common one is the rice leaf roller (Cnaphalocrocis medinalis). Damage characteristics: the larvae bind silk to roll rice leaves lengthwise into larval cases, and the larvae hide inside and feed on the mesophyll, leaving only the epidermis, forming white streaks, which reduces the 1000-grain weight of rice, increases empty grains, and causes yield loss.

Control agents: 1. Select rice varieties resistant to (or tolerant of) the pest, fertilize reasonably, so that the rice grows and develops vigorously, and prevent excessive early growth and excessive tillering as well as late-season stay-green and delayed maturity. Manage water scientifically, adjust the drainage (field-drying) time appropriately, and reduce field humidity during the larval hatching period, or irrigate with deep water for 2-3 days at the peak of pupation to kill the pupae. 2. Protect and utilize natural enemies. There are about 80 or more species of natural enemies of the rice leaf roller, and there are natural enemies that parasitize or prey on it at every stage. Egg-stage parasitic natural enemies such as Trichogramma, larval-stage ones such as the rice leaf roller braconid wasp (Apanteles), and predatory natural enemies such as spiders and frogs all have a strong controlling effect on the rice leaf roller. 3. The tillering stage and heading stage of rice are susceptible to damage by the rice leaf roller, so chemical control should be adopted. Commonly used agents include: 18% dimehypo dropping granules, monosultap, tesha, triazophos, etc.