Field evaluation of sugarcane clones against early shoot borer, Chilo infuscatellus (Snellen) and Internode Borer, Chilo saccariphagus indicus (Kapur) (Crambidae: Lepidoptera) under natural climatic conditions

Introduction

In Tamil Nadu, sugarcane is one of the important commercial crops and it has occupied a very prominent position on the agricultural map of India covering a large area in tropics as well as sub tropics. It is the major agro-industrial crop in India next to textiles. Sugar is still the most preferred sweetener and most widely used calorific food, especially in the developing countries. Sugar is today regarded as a mass consumption item and it also accounts for a large share of the total calorie intake of an average household (Pruthi, 1995) [6] . During last decades, production, productivity and sugar recovery have also shown remarkable resilience in productivity growth rate. Today there is a growing concern about susceptibility of sugar production as the growth rate has stagnated and another declining trend is seen in most of the cane growing districts. One of the reasons for the low productivity and recovery is increasing incidence of insect pests. Sugarcane crop has been associated with more than 120 species of insect pests including sap feeding, leaf feeding and stem borer (Suasa-and Allsopp, 2000) [9] . It has been estimated by Singh and Tomar (2003) [8] that the economic loss caused by the early shoot borer accounted to a 16-65% reduction in sugarcane setts and mother shoots, resulted in 22-33% losses in cane yield. Early shoot borer infestation attains peak during summer months, water scarcity and poorly maintained crop. Although integrated management measures viz., sett treatment, early planting, frequent irrigation, behavioral, biological and chemicals recommended for early shoot bore, farmers mainly rely on the usage of insecticides. Insecticides are not the best option for the control of C. sacchariphagus indicus due to the concealed habit of larvae and un amenable crop canopy (Ananthanarayana and David, 1986) [1] . Biological control and sex pheromone traps are known to minimize borer incidence levels but suffer from limitations (Mahesh et al., 2018) [4] . In this context, cultivar resistance, a major component of long-term integrated pest management strategy for sugarcane moths in many sugarcane growing regions of the world (Reay-Jones et al., 2005 [7]. ; Mahesh et al., 2018 [4]. ; Wilson et al., 2021 [10]. ) [7,4,10] , can serve as a potential tool to reduce losses caused by borers. Keeping in view the importance of sugarcane and huge damage caused by different borers, experiments were carried out to study the resistance reaction of different Initial Yield Trial (IYT), Advanced Yield Trial (AYT) clones and the standard varieties against early shoot borer, Chilo infuscatellus, internode borer, Chilo sacchariphagus indicus during 2024-2025.

Materials and methods

Two field trials were laid out during 2024-2025 at Sugarcane Research Station, Cuddalore, Tamil Nadu, India with 25 IYT clones and 15 AYT clones, including varieties in two replications under Randomized Block Design All the standard agronomical practices were followed during the cropping season to raise the crop. No plant protection measures were adopted in experimental plots. Observations were made on the damage level of early shoot borer and inter node borer under fixed plot condition. Finally mean cumulative per cent damage of early shoot borer, internode borer was worked out. In each clone variety 5 clumps of sugarcane plants were observed for early shoot borer with number of dead hearts and total number of tillers and per cent dead hearts at 35, 75 and 95 days after planting and the cumulative per cent damage of early shoot borer was worked out. For internode borer infested canes and the total cane, the mean percent internode borer damage was assessed during 5th (150 days after planting) and 7th (210 days after planting). Damage rating was also done for both the pests. For early shoot borer damage rating was 0% -15.00 incidence: Less Susceptible (LS), 15.1 -30% incidence: Moderately Susceptible (MS), > 30%: Highly Susceptible (HS). For internode borer damage rating was 0-30% incidence: Less Susceptible (LS), 30.1 -50% incidence: Moderately Susceptible (MS), > 50%: Highly Susceptible (HS).

Results and Discussion

The results of the field reaction on the damage level of early shoot borer in the IYT clones revealed that the cumulative mean per cent damage of early shoot borer ranged from 12.20(C22051) to 36.98(C22017). Four clones Viz., C22051, C22133, C22230 and C22 315 were registered as less susceptible with mean cumulative damage of 12.29, 13.10, 13.26 and 14.80 per cent respectively (Table 1). The results of the field reaction on the damage level of inter node borer in the IYT clones revealed that the cumulative mean per cent damage of internode borer ranged from 11.65(C22044) to 40.85(C22051). Nineteen clones Viz., C22002, C22003, C22011, C22014, CoV09356, C22017, C22020, C22038, C22044, Co86032, C22133, C22224, C22228, C22230, C222058, C22283, C22 315 and CoC13339 were categorized as less susceptible (Table 2). The results of the field reaction on the damage level of early shoot borer in the AYT clones revealed that the cumulative mean per cent damage of early shoot borer ranged from 14.88(C16338) to 33.61(C21033). The clone C16338 was found less susceptible with mean cumulative damage of 14.88. The mean damage grade of Crown mealy bug and pokkah boeng disease ranged from 1.10 (C16338) to 2.20(Co 11015) (Table 3). The results of the field reaction on the damage level of inter node borer in the AYT clones revealed that the cumulative mean per cent damage of internode borer ranged from 23.80(C20085) to 36.75(C21033). Thirteen clones Viz., C16338, C18011, C18200, C19024, Co11015, C19028, C20007, C20072, Co86032, C20085, C21036, C21037 and CoC1333 were rated as less susceptible (Table 4). Higher infestation in loose sheath-clasp varieties suggested their suitability since tight leaf sheath is known to act as an adverse barrier for initial establishment of neonate larvae (Easwaramoorthy and Nandagopal 1986) [3]. , and it may also render leaf axils inaccessible for pupation. Such a trend was noticed earlier with the borer even in S. barberi clones (Mahesh et al., 2019) [5]. Cane length, and length and girth of vulnerable portions are known to positively influence borer infestation in genotypes (Asha et al., 2019) [2] .

Conclusion

Field reaction on the damage level of early shoot borer in the IYT clones revealed that the cumulative mean per cent damage of early shoot borer ranged from 12.20 (C22051) to 36.98(C22017). Damage level of inter node borer in the IYT clones revealed that the cumulative mean per cent damage of internode borer ranged from 11.65(C22044) to 40.85(C22051). Damage level of early shoot borer in the AYT clones revealed that the cumulative mean per cent damage of early shoot borer ranged from 14.88(C16338) to 33.61(C21033). The results of the present investigation would be useful for the breeders to evolve suitable improved varieties of sugarcane having less susceptibility to early shoot borer and internode borer.

References

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