Silicon impedes stalk penetration by the borer Eldana saccharina in sugarcane

Many plants grown in soils amended with silicon (Si) display increased levels of resistance to attack by insect herbivores. This study aimed to determine if Si treatment impeded Eldana saccharina Walker (Lepidoptera: Pyralidae) stalk penetration and subsequent damage, as well as borer mass gain, on the node and internode of a susceptible (N11) and a resistant (N33) sugarcane cultivar. Sugarcane [Saccharum spp. (Poaceae)] cultivars were grown in a pot trial in Si‐deficient river sand, with (Si+) and without (Si–) calcium silicate. Sugarcane was infested with 2‐week‐old E. saccharina larvae and harvested at four times, 24, 48, 72, and 96 h after infestation. Silicon‐treated plants showed significant increases in Si content compared to controls, and the external rind was significantly harder for Si+ cane than Si– cane. Silicon treatment significantly decreased borer penetration, stalk damage, and larval mass gain. The results are consistent with the hypothesis that Si contributes to sugarcane stalk borer resistance by impeding larval penetration. Silicon appears to contribute to the suppression of E. saccharina directly through reduced larval growth and feeding damage to the crop, and indirectly by delaying stalk penetration, resulting most likely in increased exposure time of young larvae to natural enemies, adverse climatic factors, or control measures that target young larvae (e.g., insecticides).     

Calcium silicate enhances resistance of sugarcane to the African stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae)

Abstract

• 1 The stalk borer Eldana saccharina is the most destructive pest in sugarcane in South Africa. This study investigated: (1) the potential of applied silicon in enhancing plant resistance of sugarcane to E. saccharina, using calcium silicate as a carrier; (2) whether there was any interaction between cane variety (and stalk borer resistance) and silicon treatment.
• 2 Six commercial varieties of sugarcane were treated in a pot‐plant trial with two levels (5000 and 10 000 kg/ha) of calcium silicate. After artificial infestation with E. saccharina, response to the treatments was assessed in terms of borer numbers and mass, and stalk damage.
• 3 Calcium silicate significantly enhanced resistance at the higher rate compared with the control. Borer mass was reduced by 19.8% and stalk length bored by 24.4%. Lower treatment values were intermediate between those of the higher treatment and the control.
• 4 The interaction between variety and Si treatment was not significant when varieties were examined individually in the analysis. However, the interaction was significant for borer mass when varieties were grouped according to their resistance characteristics. Susceptible varieties might benefit more from treatment with silicon than resistant ones, as resistant varieties showed no significant effect of silicon.
• 5 All varieties had increased silicon content due to the treatments, but differed appreciably in stalk silicon content at the different treatment levels. Similarly, within varieties, stalk silicon content did not correspond consistently with borer response patterns and silicate application rates.

     

Soil silicon amendments increase resistance of sugarcane to stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae) under field conditions

Background and aims

Soil amendment with silicon (Si) can significantly increase resistance of susceptible sugarcane cultivars grown in pots to stalk borer Eldana saccharina (Lepidoptera: Pyralidae). This study tested the hypothesis that a single application of silicate can increase resistance to E. saccharina and increase yield in field-grown sugarcane.

Methods

Two Si materials (Calmasil® and Slagment® at 4 and 8 t/ha) were applied at planting to a field trial extending over three successive crops and incorporating three sugarcane cultivars varying in borer susceptibility.

Results

Both materials, especially Slagment, significantly increased soil, leaf and stalk Si content, but leaf Si levels seldom exceeded 0.5 %. Silicon treatment significantly reduced percent stalks bored in all three crops and stalk length bored in the second ratoon crop, but did not affect borer numbers per 100 stalks (E/100) or increase cane or sucrose yield. Borer damage and E/100 were significantly and consistently reduced in the resistant cultivar.

Conclusions

We argue that if leaf Si% in field sugarcane can be elevated to or exceed 0.8 %, using materials that release Si slowly, substantial reductions in stalk damage and sucrose loss could be achieved in susceptible cultivars in low-Si soils.     

Interactions between Fusarium species from sugarcane and the stalk borer, Eldana saccharina (Lepidoptera: Pyralidae)

In this study, beneficial relationships between Fusarium species in sugarcane and the stalk borer, Eldana saccharina (Lepidoptera: Pyralidae) were demonstrated in vitro . In addition, Fusarium species with antagonistic properties were found to inhabit sugarcane. Attenuated Fusarium isolates from sugarcane stalks collected across the South African sugar industry were incorporated into diet formulated to mass rear E. saccharina . Of the over 200 Fusarium isolates obtained, 10 that significantly improved the survival and development of E. saccharina larvae and considered to be beneficial were selected for further study, as were 10 that were detrimental or antagonistic to the stalk borer. Twelve of the selected isolates were identified as F. sacchari by direct sequencing of translation elongation factor-1α fragments, eight of which resulted in reduced numbers of surviving larvae and significantly lower larval masses. F. proliferatum isolates resulted in increased survival and mass of E. saccharina and three of the five isolates assigned to the F. pseudonygamai group enhanced E. saccharina development. Results from olfactory choice experiments suggested the production of attractive and repellent metabolites by certain isolates. Findings from this study may offer additional or alternative strategies for managing E. saccharina infestation of sugarcane.     

Water stress augments silicon-mediated resistance of susceptible sugarcane cultivars to the stalk borer Eldana saccharina (Lepidoptera: Pyralidae)

Silicon (Si) can improve resistance of plants to insect attack and may also enhance tolerance of water stress. This study tested if Si-mediated host plant resistance to insect attack was augmented by water stress. Four sugarcane cultivars, two resistant (N21, N33) and two susceptible (N26, N11) to Eldana saccharina Walker were grown in a pot trial in Si-deficient river sand, with (Si+) and without (Si-) calcium silicate. To induce water stress, irrigation to half the trial was reduced after 8.5 months. The trial was artificially infested with E. saccharina eggs after water reduction and harvested 66 days later. Silicon treated, stressed and non-stressed plants of the same cultivar did not differ appreciably in Si content. Decreases in numbers of borers recovered and stalk damage were not associated with comparable increases in rind hardness in Si+ cane, particularly in water-stressed susceptible cultivars. Overall, Si+ plants displayed increased resistance to E. saccharina attack compared with Si- plants. Borer recoveries were significantly lower in stressed Si+ cane compared with either stressed Si- or non-stressed Si- and Si+ cane. Generally, fewer borers were recovered from resistant cultivars than susceptible cultivars. Stalk damage was significantly lower in Si+ cane than in Si- cane, for N21, N11 and N26. Stalk damage was significantly less in Si+ combined susceptible cultivars than in Si- combined susceptible cultivars under non-stressed and especially stressed conditions. In general, the reduction in borer numbers and stalk damage in Si+ plants was greater for water-stressed cane than non-stressed cane, particularly for susceptible sugarcane cultivars. The hypothesis that Si affords greater protection against E. saccharina borer attack in water-stressed sugarcane than in non-stressed cane and that this benefit is greatly enhanced in susceptible cultivars is supported. A possible active role for soluble Si in defence against E. saccharina is proposed.     

Mechanism of resistance to the spotted stalk borer,Chilo sacchariphagus,in the sugarcane cultivar R570

Resistance in sugarcane [Saccharum spec. (Poaceae)] to the spotted stalk borer, Chilo sacchariphagus (Bojer) (Lepidoptera: Pyralidae), was studied by comparing feeding behaviour on resistant cv. R570 and susceptible cv. R579. In a field survey, the feeding behaviour of C. sacchariphagus larvae was described to identify their feeding sites on the plant. In a greenhouse artificial infestation study, we compared the establishment of larvae on potted plants. In laboratory choice and no‐choice experiments, we studied the establishment of larvae on plant organs (stalk, sheath, leaf spindle). Study of the feeding behaviour showed that: (1) first to fourth instars are able to feed on stalk, sheath, and leaf spindle, (2) boring into the stalk occurs mostly in the four uppermost internodes, and (3) most young larvae bore through the abaxial surface of leaf sheaths to reach the stalk. In greenhouse experiments, we observed an early two‐fold reduction of the number of larvae on R570 plants within the first 48 h after infestation. In laboratory experiments, larval antixenosis was demonstrated at the abaxial surface of R570 leaf sheath, but was observed neither in the leaf spindle nor in the stalk. First, second, and third instars were susceptible to this antixenosis. We hypothesize that the main resistance mechanism in R570 is an early reduction of larval establishment on plants, due to antixenosis located at the abaxial surface of leaf sheaths.     

Silicon-mediated resistance of sugarcane to Eldana saccharina Walker (Lepidoptera: Pyralidae): effects of silicon source and cultivar

Abstract:  The effects of four silicon sources – a USA calcium silicate, a local (South African) calcium silicate, Slagment^® and fly ash – on the resistance of sugarcane cultivars (two resistant and two susceptible) to Eldana saccharina Walker (Lepidoptera: Pyralidae) were studied in a potted sugarcane trial. Silicon sources were applied at 5000 or 10 000 kg/ha for the calcium silicates and Slagment; fly ash was applied at 15 000 or 30 000 kg/ha. The greatest increase in plant silicon content (particularly in stalks) was recorded for plants treated with local calcium silicate. Silicon uptake did not vary significantly between the susceptible and resistant cultivars, although the resistant cultivars had inherently higher silicon content than the susceptible ones. Treatment with silicon significantly reduced borer damage and borer performance at the higher treatment level. In general, borer damage and performance decreased with increasing rates of applied silicon and both variables were inversely related with per cent stalk silicon. On average, the higher silicon rate reduced damage by 34% in the susceptible cultivars and by 26% in the resistant cultivars, supporting the argument that susceptible cultivars benefit more from silicon treatments than resistant ones. We propose that calcium silicate amendments could be employed in the integrated, area-wide management of E. saccharina and in the management of soil acidity, both of which are widespread problems in the South African sugar industry.     

Genetic structure and relationships of four populations of the stalk boring moth, Eldana saccharina

Twenty-seven protein coding loci were examined by means of horizontal starch gel electrophoresis in samples of larvae from four populations of the stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae) in Natal, South Africa. The populations were collected in two localities approximately 250 km apart. In each locality a sample was obtained from sugarcane and also from the locally most abundant indigenous host plant of this insect (Cyperuspapyrus L. in one locality and C. dives Delile - synonomous with C. immensus CB CI. - in the other). More than one allele was detected at eight of the loci in all four populations and at a further locus in three of the populations; the other 18 loci were monomorphic for the same allele in all populations. Average expected heterozygosity over the 27 loci was approximately 0.12 in all populations. Genetic distances among the populations were small, but were greater between the two populations from the indigenous hosts and the two from sugarcane than within either of these pairs of populations. Possible explanations of these results are discussed.     

Bio-assay study of response by a parasitoid to frass and feeding substrates of its host, the stalk borer Eldana saccharina

In Petri dish and olfactometer tests Goniozus natalensis Gordh (Hymenoptera: Bethylidae) exhibited a host-searching response upon contact with, and at a short distance from, frass of its natural host, Eldana saccharina Walker (Lepidoptera: Pyralidae), whichever the substrate on which E. saccharina had been feeding. The substrates were two host plants, sugarcane or Cyperus papyrus L.; diet media based respectively on sugarcane, papyrus, or cellulose; or a synthetic diet medium, containing no plant material. Host-searching behaviour increased in intensity with age and after mating of G. natalensis females. Parasitoids responded similarly to frass produced by male and female E. saccharina larvae. The substrates themselves elicited little response in G. natalensis. Frass of another borer, Sesamia calamistis Hamps. (Lepidoptera: Noctuidae), fed on sugarcane-based medium, also elicited little response in G. natalensis. The results suggest that frass of E. saccharina larvae contains a material, evidently volatile, to which their parasitoid G. natalensis responds, irrespective of the substrate on which the E. saccharina subsist.     

Biocontrol of the sugarcane borer Eldana saccharina by expression of the Bacillus thuringiensis cry1Ac7 and Serratia marcescens chiA genes in sugarcane-associated bacteria

The cry1Ac7 gene of Bacillus thuringiensis strain 234, showing activity against the sugarcane borer Eldana saccharina, was cloned under the control of the tac promoter. The fusion was introduced into the broad-host-range plasmid pKT240 and the integration vector pJFF350 and without the tac promoter into the broad-host-range plasmids pML122 and pKmM0. These plasmids were introduced into a Pseudomonas fluorescens strain isolated from the phylloplane of sugarcane and the endophytic bacterium Herbaspirillum seropedicae found in sugarcane. The ptac-cry1Ac7 construct was introduced into the chromosome of P. fluorescens using the integration vector pJFF350 carrying the artificial interposon Omegon-Km. Western blot analysis showed that the expression levels of the integrated cry1Ac7 gene were much higher under the control of the tac promoter than under the control of its endogenous promoter. It was also determined that multicopy expression in P. fluorescens and H. seropedicae of ptac-cry1Ac7 carried on pKT240 caused plasmid instability with no detectable protein expression. In H. seropedicae, more Cry1Ac7 toxin was produced when the gene was cloned under the control of the Nm(r) promoter on pML122 than in the opposite orientation and bioassays showed that the former resulted in higher mortality of E. saccharina larvae than the latter. P. fluorescens 14::ptac-tox resulted in higher mortality of larvae than did P. fluorescens 14::tox. An increased toxic effect was observed when P. fluorescens 14::ptac-tox was combined with P. fluorescens carrying the Serratia marcescens chitinase gene chiA, under the control of the tac promoter, integrated into the chromosome.     

Impact of mass rearing and gamma irradiation on thermal tolerance of Eldana saccharina

Mating ability, survival, and fitness of mass‐produced sterile insects when released into the wild, are critical to the success of the sterile insect technique (SIT) as a pest management strategy, but their field performance remains one of the greatest challenges. Thermal stress tolerance by irradiated insects is a determinant of sterile insect quality, hence knowledge of their physiological competitiveness is essential for developing the SIT. Here, we report the results of experiments investigating effects of laboratory rearing and increasing radiation dosage on thermal limits to activity of the adult stage of Eldana saccharina Walker (Lepidoptera: Pyralidae). The critical thermal maximum (CTmax) and critical thermal minimum (CTmin) were assayed using a dynamic method on both sexes of E. saccharina moths in laboratory vs. wild populations (to determine effect of rearing history). Furthermore, the laboratory population was exposed to 150, 200, and 250 Gy, to determine the effect of radiation dose. Laboratory‐reared E. saccharina were more heat tolerant compared to wild moths for both sexes (CTmax = 44.5 vs. 44.3 °C), whereas in the case of CTmin (3.7 vs. 4.4 °C), wild moths were more cold tolerant than their laboratory‐reared counterparts. Irradiation had a negative effect on both CTmax and CTmin. Moths treated at the lowest radiation dose were more cold and heat tolerant than those treated at the highest dosages (CTmin = 4.5 vs. 6.2 °C; CTmax = 43.9 vs. 43.5 °C), thereby reinforcing the importance of lower dosages rather than those that induce full sterility against E. saccharina. In general, sex had no influence on critical thermal limits in all moth treatments except for those irradiated at 150 Gy. The data presented in this article provide evidence that increasing radiation dose impacts on fitness of laboratory‐produced moths relative to their wild counterparts, which in turn could affect the effectiveness of the SIT programme.     

Hydraulic architecture of sugarcane in relation to patterns of water use during plant development*

Hydraulic conductance was measured on leaf and stem segments excised from sugarcane plants at different stages of development. Maximum transpiration rates and leaf water potential (Ψ_L) associated with maximum transpiration were also measured in intact plants as a function of plant size. Leaf specific hydraulic conductivity (L_sc) and transpiration on a unit leaf area basis (E) were maximal in plants with approximately 0.2 m² leaf area and decreased with increasing plant size. These changes in Fand L_sc were nearly parallel, which prevented φ_L in larger plants from decreasing to levels associated with substantial loss in xylem conductivity caused by embolism formation. Coordination of changes in E and leaf hydraulic properties was not mediated by declining leaf water status, since φ_L increased with plant size. Hydraulic constrictions were present at nodes and in the node-leaf sheath-leaf blade pathway. This pattern of constrictions is in accord with the idea of plant segmentation into regions differing in water transport efficiency and would tend to confine embolisms to the relatively expendable leaves at terminal positions in the pathway, thereby preserving water transport through the stem.     

Additive and nonadditive effects of serial applications of gibberellic acid on sugarcane internode growth

Sugarcane (Saccharum spp. hybrids) plants were exogenously supplied with, 0, 1.0, 1.5, and 2.0 mg gibberellic acid (GA₃) per stalk in single and multiple applications. Increases in stalk fresh weight, total stalk length, and lengths of individual internodes were primarily a function of the interval between applications. Applications produced additive growth responses at 15- and 30-day intervals but not at 0- and 45-day intervals.     

Growth and metabolism in sugarcane are altered by the creation of a new hexose-phosphate sink

An efficient in planta sugarcane-based production system may be realized by coupling the synthesis of alternative products to the metabolic intermediates of sucrose metabolism, thus taking advantage of the sucrose-producing capability of the plant. This was evaluated by synthesizing sorbitol in sugarcane (Saccharum hybrids) using the Malus domestica sorbitol-6-phosphate dehydrogenase gene (mds6pdh). Mature transgenic sugarcane plants were compared with untransformed sugarcane variety Q117 by evaluation of the growth, metabolite levels and extractable activity of relevant enzymes. The average amounts of sorbitol detected in the most productive line were 120 mg/g dry weight (equivalent to 61% of the soluble sugars) in the leaf lamina and 10 mg/g dry weight in the stalk pith. The levels of enzymes involved in sucrose synthesis and cleavage were elevated in the leaves of plants accumulating sorbitol, but this did not affect sucrose accumulation in the culm. The activity of oxidative reactions in the pentose phosphate pathway and the non-reversible glyceraldehyde-3-phosphate dehydrogenase reaction were elevated to replenish the reducing power consumed by sorbitol synthesis. Sorbitol-producing sugarcane generated 30%-40% less aerial biomass and was 10%-30% shorter than control lines. Leaves developed necrosis in a pattern characteristic of early senescence, and the severity was related to the relative quantity of sorbitol accumulated. When the Zymomonas mobilis glucokinase (zmglk) gene was co-expressed with mds6pdh to increase the production of glucose-6-phosphate, the plants were again smaller, indicating that glucose-6-phosphate deficiency was not responsible for the reduced growth. In summary, sorbitol hyperaccumulation affected sugarcane growth and metabolism, but the outcome was not lethal for the plant. This work also demonstrated that impressive yields of alternative products can be generated from the intermediates of sucrose metabolism in Saccharum spp.     

Natural lignin modulators improve bagasse saccharification of sugarcane and energy cane in field trials

The burgeoning cellulosic ethanol industry necessitates advancements in enzymatic saccharification, effective pretreatments for lignin removal, and the cultivation of crops more amenable to saccharification. Studies have demonstrated that natural inhibitors of lignin biosynthesis can enhance the saccharification of lignocellulose, even in tissues generated several months post-treatment. In this study, we applied daidzin (a competitive inhibitor of coniferaldehyde dehydrogenase), piperonylic acid (a quasi-irreversible inhibitor of cinnamate 4-hydroxylase), and methylenedioxy cinnamic acid (a competitive inhibitor of 4-coenzyme A ligase) to 60-day-old crops of two conventional Brazilian sugarcane cultivars and two energy cane clones, bred specifically for enhanced biomass production. The resultant biomasses were evaluated for lignin content and enzymatic saccharification efficiency without additional lignin-removal pretreatments. The treatments amplified the production of fermentable sugars in both the sugarcane cultivars and energy cane clones. The most successful results softened the most recalcitrant lignocellulose to the level of the least recalcitrant of the biomasses tested. Interestingly, the softest material became even more susceptible to saccharification.     

江苏棉区种植转基因抗虫棉GK22对棉田害虫、杂草种群的影响

2001年在江苏选择南京、盐城两地,试验观察转Bt基因抗虫棉GK22的种植,对棉田害虫及杂草种群变动的影响,结果是：咀嚼式口器害虫的棉铃虫（Helicover pa armigera),红铃虫（Pectinophora goosypiella),玉米螟（Ostrinia nubilalis),金刚钻（Earias cupreoviridis),棉不造桥虫（Anomis flava),棉大卷叶虫（Adoxophyes orana)等虫口数量,蕾铃被害均表现出较好的控制效果,处理区咀嚼式口器害虫的幼虫总 量,比对照区分别减少92．51％,78．4％,其中：棉铃虫幼虫数量分别减少88．3％,72．9％,蕾铃被害虫减少87．5％,90．7％,74．11％,55．85％,红铃虫虫花减少74．4％,51．64％,铃内活虫减少90％,100％,玉米螟虫口减少72．7％,100％,金钢钻,造桥虫,卷叶虫虫口减少93％以上,对刺吸式口器盲蝽象（Adelphocoris suturalis),棉蚜（Aphis gossyppii),棉红叶螨（Tetranychus cinnabariuns)等害虫,试验区和对照区种群消长动态趋势基本一致,差异不显,两试对杂草种类及数量调查,抗虫棉区和对照区差异亦不明显。     

Identification and genetic diversity of Fusarium sacchari associated with pokkah boeng disease of sugarcane in Northeast Brazil

Isolates from the Fusarium fujikuroi species complex, mainly F. sacchari, have been reported to be the causal agents of pokkah boeng in sugarcane in Brazil. However, inadequate information was available on the occurrence and genetic diversity of F. sacchari in Northeast Brazil, which is a limiting factor on management. Thus, isolates of F. subglutinans sensu lato from sugarcane plants with symptoms of pokkah boeng were evaluated using the sexual cross-fertility to determine species. All the isolates produced black perithecia when they were crossed with the test isolates of F. sacchari. Three weeks after the crossing, the formation of fertile ascospores cirri was observed. Thirty-four isolates were self-sterile hermaphrodites, while 21 were fertile only as males. Five isolates were homothallic. The effective size [N_e(f)] of the population as a function of the frequency of hermaphrodites and female sterile strains was 95.5%. The F. sacchari isolates were separated into four genetic groups independent of geographic location. The mean of polymorphism among all populations was 79%, and the average unbiased genetic diversity (uh) was considered moderate (0.31). This study in addition to confirming that F. sacchari as the main species associated with pokkah boeng in sugarcane in Northeast Brazil, reveals the relationship of mating type and genetic diversity of F. sacchari. The unrestricted gene flow between regions is probably the best explanation for the low geographic correlation. This knowledge will help in the adoption of management measures with fungicides or resistant cultivars.     

Complete chloroplast genomes of Saccharum spontaneum,Saccharum officinarum and Miscanthus floridulus (Panicoideae: Andropogoneae) reveal the plastid view on sugarcane origins

Sugarcane (Saccharum hybrid cultivar) ranks among the world's top 10 food crops and annually provides 60–70% of the sugar produced worldwide. Despite its economic importance there has been no large-scale systematics study of genus Saccharum and the existing model of sugarcane origins has remained largely unchallenged for almost 50 years. For the first time, we have assembled the complete plastid genomes of Miscanthus floridulus (first report for this genus), Saccharum spontaneum and Saccharum officinarum allowing us to elucidate the phylogenetic origins of Saccharum s.s. species. We demonstrate that Saccharum s.s. is divided into four species, with S. spontaneum diverging from the remainder of the genus about 1.5 million years ago and S. robustum diverging 750,000 years ago. Two separate lineages, one leading to S. officinarum and the other leading to modern hybrid cultivars diverged from S. robustum 640,000 years ago. These findings overturn all previous hypotheses on sugarcane origins, demonstrating that sugarcane's antecedents could not have arisen by human action. All modern cultivars share a common Polynesian origin, whereas Old World canes, S. barberi and S. sinense, cluster as a distinct S. officinarum lineage. This makes modern cultivars a distinct species of genus Saccharum, and we formally propose the name Saccharum cultum for the ancestor of all lineages currently classified as Saccharum hybrid cultivars.     

Evaluation of damage caused by stalk borers,Sesamia spp. (Lepidoptera: Noctuidae), on sugarcane quality in Iran

The noctuid stalk borers, Sesamia spp. (S. cretica Led. and S. nonagrioides Lef.), damage a considerable percentage of sugarcane internodes annually in the province of Khuzestan, Iran. A study was conducted to quantify the relationship between stalk borer damage and sugar quality to estimate the monetary loss incurred at these levels of damage at harvest time. Three commercial varieties of sugarcane (SP70‐1143, CP69‐1062 and CP48‐103) were studied to determine the effects of damage on sugar quality. Stalks were separated into seven groups: control (without damage); one to five bored internodes per stalk; and more than five bored internodes per stalk. The percentage of bored internodes and several parameters, such as pol and brix, were measured. Sugar in the control group was 123.78, 123.72 and 104.84 kg/ton for SP70‐1143, CP69‐1062 and CP48‐103, respectively. Sugar per ton, juice purity, pol and brix were all significantly inversely correlated to the percentage of bored internodes. Estimated sugar losses for every 1% bored internode were 0.17, 0.39 and 0.23% (equal to 210, 482 and 241 kg sugar) in SP70‐1143, CP69‐1062 and CP48–103, respectively. These varieties could tolerate damage of up to 18.1, 11.7 and 18.9% bored internodes, respectively, compared to the control. Regression slopes for CP69‐1062 were slightly higher than those of the other two varieties. Therefore, based on quality damage, CP69‐1062 is susceptible to stalk borer damage.