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Challenges and Strategies in Managing Rice for Higher Productivity in the Flood-prone Environment: Arthropod and Vertebrate Pest Management in Bangladesh

Z. Islam
Entomology Division, Bangladesh Rice Research Institute, Gazipur-1701, Bangladesh

D. Catling
Department of Agronomy nad Land Improvement, Ministry of Agriculture, Forestry and Fisheries, Phnom Penh, Cambodia

Abstract/ Executive Summary:

Deepwater rice (DWR) is grown on the floodplains and deltas of Bangladesh. Its coverage has declined from 2.09 million ha to about 0.80 million ha since the late 1960s, mainly because of an expansion of the irrigated boro (winter rice) crop. Deepwater rice hosts a large complex of arthropods (74 insects, one crab, and a snail) and three vertebrate (two rats and a bird) pests. More than 40 species of parasitoids and a similar number of arthropod predators were identified from DWR fields. Among the pest complex, yellow stem borer, Scirpophaga incertulas (Walker) (Pyralidae); bandicoot rats, Bandicota bengalensis (Gray & Hardwick) and B. indica (Bechstein) (Rodentia); and rice hispa, Dicladispa armigera (Olivier) (Chrysomelidae), are major pests. The rice mealy bug, Brevennia rehi (Lindinger)(Pseudococcidae); pyralid leaffolders (three species); the ear-cutting caterpillar, Mythimna separata (Walker) (Noctuidae); flea beetle, Chaetocnema basalis Baly (Chrysomelidae); acridid and tettigonid grasshoppers (11 species); field cricket, Euscyrtus concinnus de Haan; and rice thrips Stenchaetothrips biformis (Bagnall) (Thripidae) are sporadic pests. Yellow stem borer is well adapted to the aquatic DWR environment and its population increases rapidly during the flooding period. It is a chronic pest and it causes on average about 20% yield losses. Bandicoot rats are good swimmers and are also adapted to the aquatic environment. They concentrate on village islands at the onset of flooding and later move to flooded DWR fields and make nests out of cut DWR or water hyacinth stems. Rat populations and damage vary greatly among locations and years. High populations of rats can cause more than 60% yield losses but average loss is about 5-B%. The succulent, elongating DWR plants are attractive to rice hispa. The ear-cutting caterpillar was the most destructive pest of DWR in the past, but expansion of irrigated boro rice at the expense of DWR seems to have reduced its incidence. Rice leaffolders, grasshoppers, and field crickets are present in DWR fields throughout the season, but outbreaks do not usually occur. Rice thrips, mealy bugs, and flea beetles are not adapted to the aquatic environment and thus are troublesome only in the preflood period. The incidence of mealy bug in DWR was first recorded in 1979 and flea beetle in 1977. The economic importance of these sporadic pests is not well understood. Available management options for the major pests and future management strategies are discussed.

Keywords: Flood-prone environment, Pest management, Vertebrate, Arthropod

Location:

Start Date: 00-00-1970

End Date: 00-00-1980

Program Area: Risk Management in Agriculture

Commodity: Vertebrate, Water productivity

Objectives:

To determine the higher rice productivity in the flood-prone environment under arthropod and vertebrate pest management in Bangladesh

Methodology:

Extensive surveys undertaken in Bangladesh by the authors during the late 1970s and less frequently in the 1980s revealed a large complex of flora and fauna in the DWR environment, including 74 insects, two rodents, one crustacean, one snail, and one bird as pests of DWR in Bangladesh. A large complex of leaf eaters and leafhoppers dominates the list but most of them are minor pests or have little economic significance. Among them, yellow stem borer (YSB), rice hispa (RH), and two species of bandicoot rats are considered as major pests, and seven others-mealy bug, ear-cutting caterpillar (ECC), a complex of leaffolders (LF) and grasshoppers, field cricket, flea beetle, and thrips-are considered as sporadic or localized pests. The DWR agroecosystem shows a seasonal succession of dominant flora and fauna mainly determined by hydrological changes from preflood, flood, and flood recession (Catling and Islam 1999). The preflood period is conducive to moderate buildups of canopy-living insects, whose numbers are limited by the synchronous planting of large areas, the sparse stands, poor plant condition, and robust weeding practices (Catling 1992). Flooding profoundly influences the composition, population structure, and density of flora and fauna in DWR fields. The numbers of many arthropods decline sharply and aquatic communities quickly establish. Populations of some leafhoppers, all planthoppers, and many leaf eaters decrease and re- main at low levels for the rest of the crop season. However, the presence of succulent DWR stems and leaves and milder weather extremes are favorable for a few pests. Some pests reappear in the flood-receding period but remain in low numbers, while a few other pests can become important at the end of the season or after flowering. The ecology and damage potential of major and sporadic pests differ from each other and these were: a) Yellow stem borer, b) Bandicoot rats, c) Rice hispa, d) Rice mealy bug, e) Ear-cuting caterpillar, f) Rice leaffolders, g) Field cricket, h) Flea beetle, i) Rice leaf trips, j) Grasshoppers etc. .

Source of Information: Rice Research and Development in the Flood-Prone Ecosystem, Proceedings of the international workshop on flood-prone rice systems held in Gazipur, Bangladesh, 9-11 January 2001. International Rice Research Institute. 283 p; P251-267, ISBN 971-22-0197-X

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The DWR environment and its pests are difficult to manage. Flooding produces long fragile stems several meters in length. The plant then collapses during the flood recession period, making access to the field difficult and damaging the crop. The entangled plant mass makes the adoption of normal pest management practices extremely difficult and nearly impossible. The low economic value of the crop further discourages researchers and farmers from developing and adopting specific pest management options. Nevertheless, limited research has shown that some cultural, mechanical, and chemical control opportunities can be considered for the management of some pests. Natural biological control is at the core of pest management in DWR; therefore, the conservation of natural enemies is vital and the indiscriminate use of hazardous pesticides must be avoided at all costs. The use of pesticides in DWR poses additional dangers to water-body pollution.

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