As a new "net red" in rice in recent years, the rice stalk fly has become one of the "four major pests" that need to be paid attention to in Hunan rice plant protection. There are also hazards in the mountainous hills of the Yangtze River Rice Region, southwest china and South China Rice Region. In the past three or four years, Hunan has gradually spread and shifted from hills to plain lake areas, with a large area and a high degree of harm. What is even more worrying is that at present, there are very few effective agents for the control of rice stalk flies, and the methods are lacking, making it a nightmare for farmers and agricultural operators, just like in the face of citrus, melon and vegetable flies are pests, although they hate it to the bone, they can only sigh!
Rice stalk diving fly, belonging to the order Diptera, stalk fly family, mainly larvae harm the heart leaves, growth points and young ears of rice. The hosts are mainly: Rice Li's Grass (Youcao), Barnyard Grass and Kan Mai Niang.
First, the morphological characteristics
1. Adults. The body length is 2.2-3 mm, the wingspan is 5-6 mm, and the wingspan is 5-6 mm. The whole body is bright yellow. Divided into three parts, there is a diamond-shaped black spot on the front of the head, three black-brown longitudinal stripes on the back of the chest, and the middle one is larger and not neatly arranged. There is a black transverse band at each junction of the ventral dorsal segments. The wings are transparent , the veins are brown , the feet are yellowish brown , the abdomen is spindle-shaped , and the abdomen is pale yellow. (Adults are shown in the figure below.) Source Hunan Plant Protection, invasion and deletion)
Rice stalk flycatcher: adult frontal
Rice stalk flycatcher: adult back
2. Larvae. Maggot-shaped, about 6 mm long when mature, slightly spindle-shaped, 11 segments, the early milky white or yellowish white, the tail end is divided into double forks.
Symptoms of harm in the differentiation phase of young ears. The larvae of the rice stalk fly are very small and have double forks at the tail end. Taken in Xiangyin, Hunan in 2019.
3. Pupae. It is yellowish brown in color, and the tail is similar in shape to that of a larvae, and is double-forked. (See figure below.) Source Hunan Plant Protection, invasion and deletion)
Larvae and pupae of rice stalk diving flies
Second, the occurrence and harm
1. Occurrence of regularity.
The larvae hatch at 4-6 a.m., and the hatching larvae move down with dew, burrow into the leaf sheath from the leaf pillow, and then invade into the heart leaf (similar to the trajectory of the 1st instar larvae of dimorph). Without dew, the larvae cannot walk and invade, and after about 2-3 hours they will die due to dehydration of the body. 5-7 days after the larvae burrow into the rice plant, symptoms of victimization gradually appear on the new leaves. From the analysis and summary of the situation in recent years, the harm of larvae is "threefold": the harm is heavy in the hilly fields in the mountainous areas, the harm is heavy in the young and tender rice seedling fields, and the rainy and rainy during the summer solstice to the peak of the summer egg incubation period is more harmful.
2. Symptom manifestations
Rice stalk fly larvae burrow into the heart leaf and harm the heart leaf, growth point and young ears. At the seedling stage, a number of oval or long strips of small cracks or holes grow, and later develop into longitudinal fissures and long strips, resulting in leaf fragmentation and distortion or wilting of new leaves drawn out. The tillers of the affected plants increased, the plants dwarfed, the panicle extraction was delayed, the panicle became smaller, and the grain rate increased. After the injury of the young panicle formation stage, a twisted short white panicle appears, the shell turns white, the panicle is incomplete, or it becomes a white panicle.
Rice is affected during tillering, and the leaves are longitudinally torn and perforated
Tillering stage: similar to the harmful symptoms of rice water weevil, but the difference is that the long stripes caused by the former hazard will perforate and rupture, leaving a layer of leaf epidermis;
After the rice weevil harms the heart leaf of rice, it will appear on the leaf that grows and will not lose its green color (see figure below);
Rice leaves are endangered by rice weevils: transverse perforations
Gestational panicle stage: the symptoms of harm are similar to the degeneration of the flowers, the difference is: the young ears encounter adverse external conditions (temperature, light, fertilizer, water) during the differentiation period, so that the flowers degenerate, and become white after extraction, without pores; rice stalk diving flies will leave holes in the white shell and have yellow-brown discoloration (see figure below).
Rice stalk fly endangers rice ears (source network, invasion and deletion)
Life history: According to the information of Hunan Plant Protection and Plant Inspection Network, about 3 generations a year occur in Hunan (a few have 4 generations), with adults or larvae overwintering on weeds. The first generation of adults, in late March and early April, fly to the seedlings and hondas to lay their eggs in the leaf sheath and leaf back. In early and mid-April, they hatch into larvae and burrow into the heart leaves. In mid-May, the mature larvae crawl to the leaf sheath near the leaf tongue to pupate; in mid-June, the 2nd generation of adults is at its peak, laying eggs in the middle and late rice seedling fields, and the second generation of larvae are infested from late June to early July; the 3rd generation of adults appears in August, and begins to lay eggs on the overwintering host in September, and the larvae hatch and burrow into the heart leaves for wintering. Adults tend to feather in the morning and are active during the day. After 1-3 days after feathering, both male and female can repeat the tail 3-4 times. Eggs are usually laid 2-5 days after feathering, but the second generation of adults can lay eggs for up to 22 days before spawning. Adults have the characteristic of laying eggs in tender green rice fields.
Third, prevention and control methods
1. Agricultural control. Timely removal and elimination of weeds in the field after winter rice harvest to reduce the source of overwintering insects; unified farming methods and time to reduce "bridge fields"; avoid adult and larval harm when sowing; control of field humidity, high temperature and drought are not conducive to its occurrence;
2. Physical prevention and control. Use sexual trapping agents to trap adult insects, poisonous bait and food traps, etc., and reduce the amount of eggs laid;
3. Chemical control. Take the second generation in mid-to-late June as the focus of prevention and control, especially to grasp the "bull nose" of the prevention and control of the rice field, do a good job of mixing seeds with medicines, and bring medicine to the field to reduce the degree of damage to Honda. Referring to the local "Disease and Pest Information", the rate of affected plants in the tillering stage was 1%, and the drug control was 3%-5% at the panicle stage. Medicament optional 20% furofuranol 20-30 g per acre.
Other agents may consider choosing a compound combination of ingredients with strong internal absorption conductivity and strong permeability to mix and quickly knock down.
The author has tried high levels of thiamethoxine and imidacloprid, and the effect has not reached the ideal level. Further tests are needed, such as thiamethoxamine, which is recommended by the local agricultural plant protection department, and please give more comments.
Although rice stalk flycatchers are currently mainly distributed in hilly and mountainous areas, it is worth paying attention to whether Hunan has gradually developed and spread to the Plain area of Dongting Lake, and whether it will expand to other rice areas in the future.