Occurrence Patterns and Control Methods of the Rice Water Weevil

The rice water weevil is an internationally recognized quarantine pest of agricultural plants. It first occurred in the Americas. In Asia, the countries where it occurs include Japan, South Korea, North Korea, and others. The place where the rice water weevil was first discovered in China was in 1987 in Tanghai County, Hebei Province.

The area where the rice water weevil was first discovered in our province was in August 1993 in Ji'an City in the Tonghua region. At present, most areas of our province have this pest to varying degrees.

I. Damage level of the rice water weevil

The rice water weevil mainly damages rice and also damages some grass family plants. Both the adults and larvae of the rice water weevil damage rice. The adults feed on the leaf mesophyll on young tender rice leaves, leaving the epidermis. The larvae eat the roots, feeding inside and on the rice roots. Larvae in the 1st to 3rd instars bore into and feed on the roots, and after the 4th instar they climb onto the rice roots and bite and feed on the root system. After the root system is bored and eaten, it turns black or rots, and the rice plants are prone to lodging in the wind. In fields where the pest occurs, yields generally decrease by 20%. In fields with severe rice water weevil occurrence, the yield reduction can reach 50 to 70%.

II. Life habits of the rice water weevil

The rice water weevil is a semi-aquatic insect. This insect has bisexual reproduction and parthenogenetic reproductive types (adults can reproduce by parthenogenesis). The rice water weevils occurring in China are all parthenogenetic reproductive type. The adults overwinter in rice straw, rice stubble, grass family weeds around paddy fields, and the soil of field ridges. The overwintering generation adults begin to revive and become active in spring when the temperature reaches about 10°C. After reviving, they first feed on the new leaves of grass family crops, and after rice is transplanted, they enter the paddy fields to cause damage.

III. Characteristics of the rice water weevil

This pest has strong stress resistance, tolerates starvation, tolerates low temperatures, has a high reproduction rate (each adult can lay 50 to 75 eggs), and has a wide host range.

The rice water weevil spreads quickly. This pest can crawl, is good at flying, and can swim. It can spread through water flow, airflow, and transportation vehicles.

IV. Control methods for the rice water weevil

In areas where the rice water weevil has not occurred, its introduction into the local area must be controlled. Plant quarantine regulations should be strictly followed. Do not introduce seeds from epidemic areas, and do not transport rice straw and rice straw products from epidemic areas or occurrence areas.

Control measures in occurrence areas:

1. Rational fertilization. Soil testing and fertilizer recommendation should be carried out, supplementing whatever is deficient. Too much nitrogen fertilizer easily causes an increase in pest population density.

2. Clear weeds. In autumn, winter, and spring, weeds around paddy fields should be removed or burned, so that the pest loses its overwintering sites and is directly eliminated.

3. In view of the phototaxis of the rice water weevil adults, black light lamps can be set up near paddy fields for trapping and killing.

4. Chemical pesticide control. At present, the chemical pesticides that have been screened out with relatively good control effects against the rice water weevil include: Daolefeng, Weidao emulsifiable concentrate, Xiangchongjing, Shachongshuang, and others.

In control methods, joint control should be carried out with villages and settlements as units, and the "four unifications" should be achieved. That is, unified organization, unified pesticide purchase, unified timing of pesticide application, and unified inspection. This helps improve the control effect. The control timing should be based on local actual conditions. Generally, the overwintering generation adults are controlled from June 5 to 10, and the new generation adults are controlled in early August.