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The impact of yellow stem-borer, Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae), on deepwater rice, with special reference to Bangladesh
Abstract
Using several methods, claims that stem-borers, especially Scirpophaga incertulas (Walker), cause serious crop loss in deepwater rice were tested in Bangladesh. Insecticides were used to control different borer broods. Early season, pre-flood applications reduced infestation, but did not affect yield. One to three mid- to late-season applications of monocrotophos at 250 g a.i./ha significantly reduced infestation and/or whitehead numbers, with yield savings (7-10%) similar to those which earlier workers obtained by applying diazinon 20 times in a season. In each of six years, tiller populations peaked before flooding, then steadily declined until harvest, but stem-borer infestation varied, remaining low until late season in two of the years. In 1981, infestation lower than 24% pre-flood and 42% at harvest did not affect yield. In 1982, eighty-four correlation calculations showed no consistent significant effects of infestation (27-60%, C.V. 40%) on yield (25 000 stems were dissected). Anatomical studies of elongated stems revealed S. incertulas feeding neither causes significant structural damage nor seriously interrupts nutrient flow; also, the passage of a larva through a nodal septum is not detrimental. Irrespective of stem-borer attack, the submerged lower internodes commonly die, the fibrous remains anchor the upper stem, and nodal roots take over nutrient uptake. Studies of panicle-bearing stems (n = 838) showed that, even with 97% stem infestation, most yield loss results from infestation of the terminal internode and is manifested predominantly as whiteheads. In a specific study, 94% whiteheads (n = 205) were associated with terminal internode infestation, where larval feeding in the narrow stem had disrupted food conduction, so preventing grain-filling. The apparent tolerance of S. incertulas by deepwater rice varieties is consistent with their being a primitive group of cultivated rices.
... However, depending on the variety, rice can also be tolerant of stemborer feeding at relatively late crop stages despite producing WH panicles (Rubia et al., 1995;Horgan et al., 2016a). Furthermore, tolerance can have different outcomes depending on the magnitude of stemborer attack: at low stemborer pressures, compensatory growth can sometimes result in the plant overcompensating and thereby increasing biomass accumulation or yields over non-infested controls (Taylor, 1988;Islam, 1990;Taylor, 1996;Islam and Karim, 1997). This does not mean that low levels of stemborer infestation would result in higher yields for farmers because hills with relatively low damage do not occur uniformly throughout farmers' fields; therefore, overcompensation is best regarded at the plant level and not at the crop level (Table 1). ...
Research into rice-stemborer interactions for pest management has gained renewed attention in the last 10–15 years. However, recent research has tended to overlook essential concepts around the nature of stemborer rice interactions that were developed between the 1960s and early 1990s. This lack of adequate attention to issues such as tolerance, compensation, and vulnerability is apparent from the limited range of bioassays and recorded parameters currently applied during research. Furthermore, aspects of intraspecific interactions between stemborers and between rice plants, and crop-mediated interspecific interactions between stemborers as determinants of crop damage have been almost entirely omitted from recent research. This review categorizes rice-stemborer interactions to help tease apart some of the factors that contribute to differential stemborer damage and yield losses. Furthermore, based on emerging knowledge of the relationship between damage and yield losses as rice plants grow and develop, the review highlights the need for considerably more attention to aspects of plant and crop tolerance, including a need to adequately develop phenotyping methods that assess genotypic differences in the plant’s capacity to compensate for damage. Since stemborers normally occur at low densities in well-managed rice landscapes, such attention to compensation for damage will potentially increase economic thresholds and, thereby, avoid pesticide applications.
... Newly emerged larvae enter the stem for feeding on the internal tissues at vegetative and reproductive stages of the plant growth, leading to the formation of 'dead hearts' and 'white ears'. Annual losses due to rice borers are approximately 5-10%, but losses in individual fields may reach 50-60% [8][9][10]. Recovery or prevention of 5% of the losses to stem borers could feed approximately 140 million people for one year [10]. ...
Simple Summary
Yellow stem borer (YSB), is the most destructive and widely occurring pest that attacks rice throughout the growing season. Rice (Oryza sativa L.) is a major staple cereal worldwide, providing essential caloric requirements for more than half of the world’s population. Annual losses to rice borers are approximately 5–10%, but losses in individual fields may reach up to 50–60%. The use of traditional pest management strategies in controlling YSB is somewhat challenging due to its unique internal feeding habit. Genome sequence information of economically important crop pests is important for designing or developing pest-resistant rice varieties. In an approach to achieve this, we present our first-ever study on the draft genome sequence of YSB. The information provided from our current study might be useful in developing genome-based approaches for the management of pest species.
Abstract
Yellow stem borer (YSB), Scirpophaga incertulas (Walker) (Lepidoptera: Crambidae), a major monophagous insect pest of rice, causes significant yield losses. The rice–YSB interaction is very dynamic, making it difficult for management. The development of resistant lines has been unsuccessful as there are no effective resistant sources in the germplasm. Genome information is necessary for a better understanding of interaction with rice in terms of its recognition, response, and infestation mechanism. The draft genome of YSB is predicted to have 46,057 genes with an estimated size of 308 Mb, being correlated with the flow cytometry analysis. The existence of complex metabolic mechanisms and genes related to specific behavior was identified, being conditioned by a higher level of regulation. We deciphered the possible visual, olfactory, and gustatory mechanisms responsible for its evolution as a monophagous pest. Comparative genomic analysis revealed that YSB is unique in the way it has evolved. The obvious presence of high-immunity-related genes, well-developed RNAi machinery, and diverse effectors provides a means for developing genomic tools for its management. The identified 21,696 SSR markers can be utilized for diversity analysis of populations across the rice-growing regions. We present the first draft genome of YSB. The information emanated paves a way for biologists to design novel pest management strategies as well as for the industry to design new classes of safer and specific insecticide molecules.
... On the other hand, stem borers may damage only stems of a certain thickness. For example, S. incertulas larvae do not severely damage the large stems of deepwater rice, because they feed on the pith and do not damage plant tissues involved with nutrient flow (Taylor, 1988). Rice plants are able to compensate for damage by early borers (Rubia et al., 1996), but larval feeding during the booting significantly reduces yield and causes whiteheads (Chaudhary et al., 1984;K.L. Heong, unpublished material). ...
... On the other hand, stem borers may damage only stems of a certain thickness. For example, S. incertulas larvae do not severely damage the large stems of deepwater rice, because they feed on the pith and do not damage plant tissues involved with nutrient flow (Taylor, 1988). Rice plants are able to compensate for damage by early borers (Rubia et al., 1996), but larval feeding during the booting significantly reduces yield and causes whiteheads (Chaudhary et al., 1984;K.L. Heong, unpublished material). ...
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The yellow stem borer Scirpophaga incertulas is the dominant pest of rice in tropical Asia. However, the lack of genomic resources makes it difficult to understand their invasiveness and ecological adaptation. A high-quality chromosome-level genome of S. incertulas, a monophagous rice pest, was assembled by combining Illumina short reads, PacBio HiFi long sequencing, and Hi-C scaffolding technology. The final genome size was 695.65 Mb, with a scaffold N50 of 28.02 Mb, and 93.50% of the assembled sequences were anchored to 22 chromosomes. BUSCO analysis demonstrated that this genome assembly had a high level of completeness, with 97.65% gene coverage. A total of 14,850 protein-coding genes and 366.98 Mb of transposable elements were identified. In addition, comparative genomic analyses indicated that chemosensory processes and detoxification capacity may play critical roles in the specialized host preference of S. incertulas. In summary, the chromosome-level genome assembly of S. incertulas provides a valuable genetic resource for understanding the biological characteristics of its invasiveness and developing an efficient management strategy.
The role played by the lepidopteran yellow stem borer, Scirpophaga incertulas (Walker) in the life cycle of deepwater rice (Oryza sativa) is controversial. The major question is whether or not larval feeding in the elongated stems is damaging and if so, although no visible symptoms can be observed, leads to loss of yield. Drawing on evidence from entomological and agronomic studies, especially in Bangladesh and Thailand, this paper shows that there is little or no correlation between early- or mid-season borer infestation and yield; that stem density always declines from a pre-flood maximum, irrespective of borer infestation; how late-season infestations can lead to serious crop loss; and, how a promising concept for strategic timing of insecticide application was developed and tested.
Since monocrotophos was introduced for use in crop protection some 30 years ago, many new groups of insecticides have become available, ranging from traditional synthetic chemicals to natural and biological products. Nevertheless, monocrotophos has remained one of the preferred insecticides for farmers in the developing world. Its low cost and versatile activity on a wide range of pests make it the third most widely used insecticide in the world. It is currently registered and sold in more than 50 countries, including seven that are members of the Organization for Economic Cooperation and Development (OECD), of which four are also members of the European Union.
Rice is the most important food for mankind. Annual world rice production amounts to approximately 460 million tons grown on roughly 145 million ha (Norton and Way 1990). Over 90% of this area lies in Asia, while the remainder is divided among Latin America, Africa, Australia, Europe, and the United States (IRRI 1989). To keep pace with projected human population growth, rice production must increase from the 1987 levels to 20% more by 2000 and 65% more by 2020 (IRRI 1989). However, over 800 insect species attack standing and stored rice (Grist and Lever 1969). According to Pathak and Dhaliwal (1981) these pests account for rice losses of 24% while Cramer (1967) reports 35%. The importance of rice insect pests can be grasped by the fact that $910 million are spent annually in attempts to control their activities with insecticides (Woodburn 1990). Japanese rice farmers spend the most ($455 million), while farmers in developing countries spend much less per unit of production (Woodburn 1990). Furthermore, the value of insecticides applied to rice in 1988 was 15% of the total world usage of insecticides (Woodburn 1990). Thus, insect pests are serious enemies to rice production which must be protected and increased to foster human health and world peace and stability.
An Experiment for the efficacy of monomehypo 5G @ 7 kg arce-1 against rice leaf folder (Cnaphalocrocis medinalis, G.M), rice stem borers (Tryporyza spp.) and chlorpyrifos 40 EC @ 1000 ml acre-1 and effect on natural enemies (dragonflies, damselflies and green lacewings) was laid out in Randomized Complete Block Design (RCBD). Three treatments, i.e., monomehypo 5G, chlorpyrifos 40EC and a control were replicated thrice. Results showed that % leaffolder infestation level, population density of naiads and adults of dragon+damselflies and adults of green lace wings on Basmati super was not significantly different from that of Basmati-385 (P=0.20) for one tail and P
The influence of the lepidopteran stem borer Scirpophaga incertulas (Walker), the most important pest of deepwater rice (Oryza sativa) in south-east Asia, on plant and grain yield was investigated in Bangladesh during 1982–85. Four mechanisms of crop loss were identified: (i) deadhearts at the vegetative stage, (ii) loss of damaged but apparently healthy stems in flood water, (iii) white-heads at the reproductive stage and (iv) the effect of late season stem damage on panicles. A great proportion of damaged stems was not visible and damage symptoms were found to be an unreliable indicator for the assessment of borer activities in the field, and did not represent the actual yield loss. Stem damage had a negative influence on the stem density, with reduced panicle density and grain yield. Stem borer damage also seemed to reduce the elongation ability of the rice stem causing them to rot. Late season stem damage reduced the number of filled grains, mean grain weight and panicle weight and increased grain sterility. These effects were related to severity and position of damage. The average estimated yield loss due to S. incertulas was about 17% which took place during the last 11 weeks (from flood peak to crop maturity) of the deepwater rice season (32 weeks).
Yield loss from damage by yellow stem borer, Scirpophaga incertulas, was assessed in deep-water rice in Bangladesh and Thailand using five different methods. Because of the long stems and special growing conditions of the crop only three methods proved reliable: pot experiments in metal containers, potted plants exposed in the field, and floating exclusion cages in the field. Yields were reduced by 27–34%, and 1% yield loss was associated with 2% damaged stems at harvest. Yield loss was mainly due to a loss of bearing stems and lighter panicles borne by compensatory nodal tillers. A tentative damage threshold of 10% damaged stems at booting/flowering stage and 20% damaged stems at plant maturity is proposed.
In order to overcome the difficulties of applying pesticides in flooded rice, the authors designed and built a light-weight spray boom for use with a local type of boat. The 5 m long boom is equipped with four Micron rotary atomisers powered by a 12 volt car battery and can spray a 4 m swath on one side of the boat. The major pest in Bangladesh ricefields is the stem borer, Tryporyza incertulas. Field trials using this equipment to spray diazinon showed a reduction in stem borer infestation and an increase in yield.
Crop loss in deepwater rice caused by yellow stem borer (YSB)
- Taylor
Deep-water rice of East Pakistan.-pp. 1-20 presented at 13th International Rice Commission Session of FAO
- M A Chowdhury
- S M H Zaman
Effect of mechanical uprooting on the yield of deep water Aman paddy
- Alim