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.     

Influence of plant silicon and sugarcane cultivar on mandibular wear in the stalk borer Eldana saccharina

1 Silicon can increase the resistance of plants to attack by herbivorous insects. The present study aimed to determine the effect of silicon and cultivar on mandibular wear in larvae of the sugarcane stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae).
2 Four sugarcane cultivars, resistant (N21, N33) and susceptible (N11, N26) to E. saccharina were grown in a pot trial in silicon deficient river sand, with (Si+) and without (Si−) calcium silicate. Individual third-instar larvae were confined on the sugarcane stalk at three known feeding sites (leaf bud, root band and internode) and left to feed for 21 days.
3  Eldana saccharina larval heads were mounted on stubs, with the mandibles oriented horizontally and photographed under a scanning electron microscope. Mandibular wear was measured from the digital images using a quantitative method.
4 Although there was a trend for increased wear in larvae that developed on Si+ cane, no significant effect of silicon, cultivar or site on mandibular wear of E. saccharina was shown.
5 This is the first study to accurately and quantitatively measure the mandibular wear of an insect fed on Si+ plants.     

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.

     

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.     

Genetic transformation and pyramiding of aprotinin-expressing sugarcane with cry1Ab for shoot borer (Chilo infuscatellus) resistance

We evaluated the insecticidal toxicity of Cry1Aa, Cry1Ab and Cry1Ac toxins against neonate larvae of sugarcane shoot borer Chilo infuscatellus Snellen (Lepidoptera: Crambidae) in vitro on diet surface. With the lowest LC₅₀ value, Cry1Ab emerged as the most effective among the three toxins. Sugarcane cultivars Co 86032 and CoJ 64 were transformed with cry1Ab gene driven by maize ubiquitin promoter through particle bombardment and Agrobacterium-mediated transformation systems. Gene pyramiding was also attempted by retransforming sugarcane plants carrying bovine pancreatic trypsin inhibitor (aprotinin) gene, with cry1Ab. Southern analysis confirmed multiple integration of the transgene in case of particle bombardment and single site integration in Agrobacterium-mediated transformants. The expression of cry1Ab was demonstrated through Western analysis and the toxin was quantified using ELISA. The amount of Cry1Ab protein in different events varied from 0.007 to 1.73% of the total soluble leaf protein; the events transformed by Agrobacterium method showed significantly higher values. In in vivo bioassay with neonate larvae of shoot borer, transgenics produced considerably lower percentage of deadhearts despite suffering feeding damage by the borer compared with the untransformed control plants. Expressed Cry1Ab content was negatively related to deadheart damage. Aprotinin-expressing sugarcane pyramided with cry1Ab also showed reduction in damage. The potential of producing sugarcane transgenics with cry1Ab and aprotinin genes resistant to early shoot borer was discussed in the light of the results obtained.     

Host plant‐related variation in thermal tolerance of Eldana saccharina

Understanding tolerance of thermal extremes by pest insects is essential for developing integrated management strategies, as tolerance traits can provide insights into constraints on activity and survival. A major question in thermal biology is whether thermal limits vary systematically with microclimate variation, or whether other biotic or abiotic factors can influence these limits in a predictable manner. Here, we report the results of experiments determining thermal limits to activity and survival at extreme temperatures in the stalk borer Eldana saccharina Walker (Lepidoptera: Pyralidae), collected from either Saccharum spp. hybrids (sugarcane) (Poaceae) or Cyperus papyrus L. (Cyperaceae) and then reared under standard conditions in the laboratory for 1–2 generations. Chill‐coma temperature (CT_min), critical thermal maximum (CT_max), lower lethal temperatures (LLT), and freezing temperature between E. saccharina collected from the two host plants were compared. CT_min and CT_max of E. saccharina moths collected from sugarcane were significantly lower than those from C. papyrus (CT_min = 2.8 ± 0.4 vs. 3.9 ± 0.4 °C; CT_max = 44.6 ± 0.1 vs. 44.9 ± 0.2 °C). By contrast, LLT of moths and freezing temperatures of pupae did not vary with host plant [LLT for 50% (LT₅₀) of the moth population, when collected from sugarcane: ?3.2 ± 0.5 °C, from C. papyrus: ?3.9 ± 0.8 °C]. Freezing temperatures of pupae collected from C. papyrus were ?18.0 ± 1.0 °C and of those from sugarcane ?17.5 ± 1.8 °C. The E. saccharina which experienced the lowest minimum temperature (in C. papyrus) did not have the lowest CT_min, although the highest estimate of CT_max was found in E. saccharina collected from C. papyrus and this was also the microsite which reported the highest maximum temperatures. These results therefore suggest that host plant may strongly mediate lower critical thermal limits, but not necessarily LLT or freezing temperatures. These results have significant implications for ongoing pest management and thermal biology of these and other insects.     

The influence of wild and cultivatedGramineae andCyperaceae on populations of sugarcane borers and their parasites in North India

Sugarcane borers frequently inhabit wild and semi-cultivated grasses growing in the proximity of cane fields. In India, in view of the year-round cultivation of sugarcane, wild grasses are not necessary for the perpetuation of borer species, but observations indicate that certain borer species migrate from wild or other cultivated grasses to cane, thereby increasing levels of infestation in cane during certain seasons. Parasitism of borer species when present in cane is compared with that in wild or other cultivated grasses.Telenomus spp. amongst egg parasites andApanteles flavipes amongst larval parasites are striking examples of parasites which show preference for the same borer species when they occur on wild hosts than on cane, as indicated by the degrees of parasitism. It is concluded that though wild grasses do not as a rule constitute a threat to the cultivation of sugarcane, they could indirectly influence borer populations in cane, parasitism of borers and consequently the extent of damage to cane. This study also reveals thatA. flavipes is highly polyphagous, attacking a number of host species occurring on a wide variety of host plants. Despite its polyphagous nature, it has proved extremely successful againstDiatraea saccharalis in Barbados, which indicates a need for some rethinking on the use of polyphagous natural enemies in biological control programmes.     

Control of Diatraea saccharalis by the endophytic Pantoea agglomerans 33.1 expressing cry1Ac7

Despite the fact that Bacillus thuringiensis (Bt) is found in more than 90 % of the products used against insects, it has some difficulty reaching the internal regions where the larvae feed. To solve this problem, many genetically modified microorganisms that colonize the same pests have been developed. Thus, the endophytic bacterium Pantoea agglomerans (33.1), which has been recently described as a promising sugarcane growth promoter, was genetically modified with the pJTT vector (which carries the gene cry1Ac7) to control the sugarcane borer, Diatraea saccharalis. Firstly, the bioassays for D. saccharalis control by 33.1:pJTT were conducted with an artificial diet. A new in vivo methodology was also developed, which confirmed the partial control of larvae by 33.1:pJTT. The 33.1:pJTT strain was inoculated into sugarcane stalks containing the D. saccharalis larvae. In the sugarcane stalks, 33.1:pJTT was able to increase the mortality of D. saccharalis larvae, impair larval development and decrease larval weight. Sugarcane seedlings were inoculated with 33.1:pJTT, and re-isolation confirmed the capacity of 33.1:pJTT to continuously colonize the sugarcane. These results prove that P. agglomerans (33.1), a sugarcane growth promoter, can be improved by expressing the Cry protein, and the resulting strain is able to control the sugarcane borer.     

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.     

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.     

Effects of soybean proteinase inhibitor on development, survival and reproductive potential of the sugarcane borer, Diatraea saccharalis

One approach that can be employed in integrated pest management is the use of proteins with antinutritional effects on insect metabolism and development. The antimetabolic properties of soybean proteinase inhibitor (SPI) on growth of neonate larvae of the sugarcane borer, Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) have been evaluated. When incorporated into an artificial diet at 0.5% (w/w), SPI retarded growth rate and development of larvae when compared with larvae fed on artificial diet alone. However, larval survival was not significantly affected. The purpose of our research was to calculate demographic statistics for the sugarcane borer reared on diet either with or without semi-purified extract of SPI. Net reproductive rate (R ₀), instantaneous rate of increase (r _m), combined age-specific survivorship (l _x) and age specific fecundity (m _x) provide information about population growth potential. These parameters were measured in order to determine the effects of the proteinase inhibitor on the insect's population dynamics. The observed differences would potentially translate into large reductions in population growth, indicating a potential value of using SPI for protecting sugarcane plants against damage by the sugarcane borer.     

Genetic Diversity of Sturmiopsis parasitica Curran (Diptera: Tachinidae)

Sturmiopsis parasitica Curran (Diptera: Tachinidae) is a widely spread parasitoid of various lepidopteran stem borers including Eldana saccharina Walker (Lepidoptera: Pyralidae), Busseola fusca (Fuller) and Sesamia calamistis Hampson (Lepidoptera: Noctuidae) in western, eastern and southern Aenica. As the Aenican sugarcane stalk borer, E. saccharina, is currently the most economically important insect pest in South Aenican sugarcane there is an urgent need to develop a control strategy for the management of this pest. S. parasitica has been tested as a biological control agent against E. saccharina with limited success. In seeking possible reasons for this limited success we tested whether there is genetic differentiation among populations of S. parasitica and whether there are hostassociated lineages of S. parasitica enom B. fusca and E. saccharina.

To assess these hypotheses, DNA sequences of cytochrome oxidase I (COI), a mitochondrial proteincoding gene, were obtained enom fifteen specimens collected in western, eastern and southern Aenica. Phylogenetic analysis of these sequences using maximum parsimony grouped the specimens into two main clades, one of which is further subdivided. Examination of pairwise sequence divergence levels supports the hypothesis of two cryptic lineages. However, further supportive evidence is necessary before revising the taxonomy of the species.     

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.     

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.     

Organization of the retrocerebral gland system in lepidopterous larvae of the family pyralidae

The organization of the retrocerebral gland system in larvae of six species of Lepidoptera belonging to the family Pyralidae was compared using light and electron microscopy. We have demonstrated for the first time the presence of separate corpora cardiaca and corpora allata in the following economically important borers: the southwestern corn borer, Diatraea grandiosella, the sugar cane borer, Diatraea saccharalis, the European corn borer, Ostrinia nubilalis, and the rice stalk borer, Chilo plejadellus. In these species a long nervus corporis allati (ca. 300 μm) runs from the corpus cardiacum to the corpus allatum which is attached to the duct of the mandibular gland.The identity of the corpora allata of D. grandiosella was confirmed by transplantation. Corpora allata removed from pre-diapausing larvae and implanted into the haemocoele of early last stage non-diapausing larvae led to a high incidence of supernumerary larval rather than pupal ecdyses.     

Performance and preference of sugarcane borer,Diatraea saccharalis,on rice cultivars

The sugarcane borer, Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae), is a major agronomic pest in the southeastern USA. This study was conducted to investigate the performance of D. saccharalis on eight rice cultivars widely grown in Louisiana and to assess the relationship between oviposition preference and offspring performance. In a previous study, oviposition preference of sugarcane borers was found to vary on the same eight rice cultivars. In this study, variation in larval performance on the eight cultivars was observed. The overall performance of larvae in terms of relative growth rate and boring success of larvae was highest on Priscilla and Cocodrie. Larval performance was lower on the hybrid XL723, the Clearfield (herbicide‐resistant) variety CL161, and the medium grain Bengal. Also, larvae took more time to enter into the stem of the hybrid XL723 compared with Cocodrie. Significant positive correlations were observed among relative growth rate and boring success and between larval performance and oviposition preference. Significant positive correlations among measures of larval performance and oviposition preference suggest the operation of a common resistance mechanism. Results in laboratory and greenhouse extended into the field, where Cocodrie and Cheniere were the most damaged cultivars, whereas CL161 and the medium grain Jupiter were least injured in terms of average number of stem borer entry/exit holes per plant. Results from this study could contribute to the use of resistant cultivars in an integrated management program for stem borers and the resistant cultivars identified in this study could be used as sources of resistance in breeding programs for resistance against stem borers.     

Effects of artificial shade on attack by the mahogany shoot borer, Hypsipyla robusta (Moore)

Abstract

• 1 Swietenia macrophylla King (Meliaceae: Swietenioideae) provides one of the premier timbers of the world. The mahogany shoot borer Hypsipyla robusta Moore (Lepidoptera: Pyralidae) is an economically important pest of S. macrophylla throughout Asia, Africa and the Pacific. No viable method of controlling this pest is known. Previous observations have suggested that the presence of overhead shade may reduce attack by H. robusta, but this has not been investigated experimentally. This research was therefore designed to assess the influence of light availability on shoot‐borer attack on S. macrophylla, by establishing seedlings under three different artificial shade regimes, then using these seedlings to test oviposition preference of adult moths, neonate larval survival and growth and development of shoot borer larvae.
• 2 Oviposition preference of shoot borer moths was tested on leaves from seedlings grown under artificial shade for 63 weeks. A significant difference in choice was recorded between treatments, with 27.4 ± 1.5 eggs laid under high shade and 87.1 ± 1.8 under low shade.
• 3 Neonate larval survival on early flushing leaflets of S. macrophylla did not differ significantly between shade treatments. Larval growth rate, estimated by measuring daily frass width, was significantly higher for those larvae fed on seedlings from the high and medium shade treatments (0.1 mm/day), than the low shade treatment (0.06 mm/day). In laboratory‐reared larvae, the total mass of frass produced was significantly higher in the high shade treatment (0.4 g) than under the low shade treatment (0.2 g).
• 4 Longer tunnel lengths were bored by larvae in plants grown under high shade (12.0 ± 2.4 cm) than under low shade (7.07 ± 1.9 cm). However, pupal mass under low shade was 48% higher than that under the high shade treatment, suggesting that plants grown under high shade were of lower nutritional quality for shoot borer larvae.
• 5 These results indicate that shading of mahogany seedlings may reduce the incidence of shoot borer attack, by influencing both oviposition and larval development. The establishment of mahogany under suitable shade regimes may therefore provide a basis for controlling shoot borer attack using silvicultural approaches.

     

鉴定转Bt甘蔗抗条螟的方法

通过采集蔗田条螟Proceras venosatus Walker的蛹,在室内可控条件下进行羽化、交配、产卵、孵化的方式获得虫源,并将初孵幼虫接于检疫温室桶栽的13个转Bt基因甘蔗品系的心叶上,7 d后调查幼虫的生长死亡情况以及甘蔗受害程度.结果表明,综合幼虫的生长死亡情况和甘蔗受害程度二项指标,能更准确评价甘蔗的抗虫...     

Bt-maize as a potential trap crop for management of Eldana saccharina Walker (Lep., Pyralidae) in sugarcane

Abstract:  Notwithstanding the introduction of several pest management tactics, the stalk borer Eldana saccharina Walker (Lep., Pyralidae) remains the most serious pest in South African sugarcane. A novel tactic for managing this pest in sugarcane would be the use of a dead-end trap crop that attracts moths for oviposition and curtails subsequent larval development, thereby reducing pest population size. Glasshouse bioassays, in which moths chose to oviposit on maize producing Bacillus thuringiensis Cry1Ab toxin ( Bt -maize), non- Bt -maize or sugarcane of two cultivars (borer-resistant and -susceptible), showed that E. saccharina laid significantly more eggs and egg batches per dry leaf and unit mass of dry leaf on maize ( Bt or non- Bt ) than on either of the cane cultivars. When moths had a choice of ovipositing on 2-, 3-, 4- or 5-month-old maize ( Bt and non- Bt ), dry leaf number and mass of dry leaf material was significantly correlated with number of eggs and egg batches, indicating that older plants, which carried larger amounts of dry leaf matter, were more attractive for oviposition. Finally, glasshouse assays in which hatching larvae fed on 2.5-, 3.5- and 4.5-month-old Bt and non- Bt -maize plants, showed that the Cry1Ab toxin was effective in killing E. saccharina larvae in all Bt -maize plant growth stages, confirming that Bt -maize fulfilled the third requirement (curtailing larval development) of a dead-end trap crop for this pest. We argue that Bt -maize warrants further testing in the field as a trap crop, both alone and as a component of a 'push–pull' or habitat management system for E. saccharina in sugarcane.