Diatraea Saccharalis Research Articles

Resistance of Saccharine Sorghum Cultivars to Sugarcane Borer Diatraea saccharalis

The saccharine sorghum has been investigated as a complementary source of raw material for ethanol production, especially during the sugarcane off-season, however, it has been susceptible to the attack of the sugarcane borer Diatraea saccharalis. The objective of this work was to verify the effect of sorghum cultivars on D. saccharalis’ biological parameters. Cultivars, BRS 506, BRS 509 and BRS 511 were used to determine duration and survival rates of eggs, larvae, pre-pupae and pupa phases, along with larval weight and adult longevity. D. saccharalis completed its biological cycle in all treatments, however, when fed with dry extracts of BRS 509 cultivar, the net reproduction rate, the intrinsic rate of increase and the finite rate of increase was superior from the others. BRS 506 was the cultivar that negatively affected D. saccharalis’ biological parameters, with possible antibiosis effect. Based on this study, the sorghum cultivars evaluated are not recommended for a grain production system, since D. saccharalis’ larvae presented good development when fed with its dry extract incorporated into the diet.

Yield and technological quality of sugarcane cultivars under infestation of Diatraea saccharalis (Fabr., 1794)

ABSTRACT: The sugarcane borer, Diatraea saccharalis (Fabr., 1794) (Lepidoptera: Crambidae), is one of the main pests of sugarcane. This pest can reduce the quality and yield of the crop. Information on the quality and yield of cultivars in relation to the attack of sugarcane borer are necessary, since they guide the choice of the best materials for use in joint with other management tactics. Two field experiments were conducted in 2011 and 2012 to compare the quality and yield of 16 commercial sugarcane cultivars (IACSP93-3046, IACSP94-2094, IACSP94-2101, IAC91-1099, IACSP95-5000, IAC87-3396, RB92579, RB867515, RB966928, CTC2, CTC4, CTC9, CTC11, CTC15, CTC18 and SP86-0042) relative to the natural infestation of D. saccharalis. The experimental design was a randomized complete block with four replications. There was no difference between treatments for infestation index, with averages of 1.2 to 8.7% of bored internodes. Higher percentages of internodes with red rot were observed for CTC9, CTC2 and RB966928. The cultivars CTC4 and RB92579 infested with D. saccharalis resulted in lower technological quality, due the reduction in the contents of brix, apparent sucrose content (POL) and purity; and increase of the reducing sugars and, consequently, lower theoretically recoverable sugar (TRS). On the other hand, the lowest yields (t of cane ha-1) were observed for CTC18, IACSP94-2094, IACSP94-2101 and RB966928. Therefore, according to the hierarchical cluster analysis (UPGMA), the cultivars RB867515, CTC11, IAC91-1099, CTC15, SP86-0042, CTC2 and IACSP94-3046 were resistant to D. saccharalis.

Susceptibility and yield response to sugarcane borer (Lepidoptera: Crambidae) infestation among sugarcanes and sorghums with potential for bioethanol production

The U.S. Gulf Coast has ideal conditions, including abundant rainfall and a long growing season, for production of dedicated bioenergy crops. Interest in producing bioethanol from high-biomass graminaceous crops including energycanes (Saccharum spp.) and energy sorghums (Sorghum spp. hybrids) in the region has increased. However, insect pests including the sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), will likely adversely affect bioenergy crops. The impact of D. saccharalis infestations on yields of conventional and bioenergy sugarcanes and sorghums was investigated in three separate field studies conducted from 2012 to 2013. These studies compared D. saccharalis injury and crop yield parameters among insecticide-protected and unprotected plots of sugarcanes, energycanes, high biomass sorghums, and sweet sorghum. In unprotected plots, D. saccharalis injury ranged from 2.9 (resistant sugarcane) to 13.6% bored internodes (susceptible sugarcane). A resistant energycane cultivar was among the least injured (3.5% bored internodes) and demonstrated the greatest potential for bioethanol production with an average of >17,000 L/ha. Linear regressions revealed negative relationships between percentage of bored internodes and ethanol yield in all cultivars. At one location, D. saccharalis injury resulted in a 13% reduction in bioethanol production across all years and cultivars. These studies indicate D. saccharalis has potential to substantially reduce yields in bioenergy crops and pest management programs will be needed to maximize ethanol production.

Red-rot infection in sugarcane attenuates the attractiveness of sugarcane borer-induced plant volatiles to parasitoid

Fungal phytopathogens are known to induce changes in plant metabolite profile and defense levels that consequently affect insect herbivores. Although it is expected that fungal plant infection may also affect herbivore natural enemies that are guided by plant chemical cues, few studies have addressed this interaction. Here, we examined the effect of infection in sugarcane by the red-rot fungus, which is usually associated with the injury of the sugarcane-borer Diatraea saccharalis, on plant defenses by assessing borer weight gain and the attractiveness of herbivore-induced plant volatiles to the parasitoid Cotesia flavipes. Olfactometer assays and GC–MS analysis showed that although red-rot-infected plants released a different volatile blend from mock-inoculated, the wasps showed no preference for either of the two treatments. Red-rot disease also caused qualitative and quantitative changes in the volatile blend emitted by herbivore-damaged plants relative to healthy and damaged plants, such as the addition of the fungal-derived 1-octen-3-ol and either a reduction or an increase of volatiles. These differences were detected by C. flavipes, which preferred volatiles released by herbivore-damaged healthy over herbivore-damaged infected plants. When given a choice between mock-inoculated and herbivore-damaged infected plants, the wasps preferred infected ones. Sugarcane-borer larvae were larger when fed on healthy plants relative to red-rot infected sugarcane plants, indicating that parasitoid wasps likely benefit from being attracted to volatiles of healthy over infected damaged sugarcane. Although the infection did not seem to disrupt the parasitoid host-location, red-rot disease attenuates the attractiveness of herbivore-induced sugarcane volatiles to C. flavipes.

Molecular characterization and functional differentiation of three pheromone-binding proteins from Tryporyza intacta

Insect pheromone-binding proteins (PBPs) have been proposed to capture and transport hydrophobic sex pheromone components emitted by con-specific insects to pheromone receptors in the hemolymph of male antennal sensilla. In this study, field trapping results indicate that a mixture of E11–16: Ald and Z11–16: Ald can effectively attract a great number of male Tryporyza intacta. Real-time PCR results suggest that the transcript levels of three TintPBP1-3 genes are mainly expressed in the adult antennae. Fluorescence competitive binding experiments show that TintPBP1-3 proteins have great binding affinities to their major sex pheromones. Moreover, TintPBPs clearly cannot bind to other four kinds of sex pheromone components released by another sugarcane borer, Chilo venosatus and Chilo infuscatellu, which have the same host plant and live in similar habitats like T. intacta. The molecular docking results demonstrate that six amino acid residues of the three TintPBPs are crucial for the specific perception of the sex pheromone components. These results will provide a foundation for the development of novel sex pheromone analogues and blocking agents for biological control of sugarcane pests, improving their efficient monitoring and integrated management strategies in the sugarcane field.

The Endophytic Strain Klebsiella michiganensis Kd70 Lacks Pathogenic Island-Like Regions in Its Genome and Is Incapable of Infecting the Urinary Tract in Mice.

Klebsiella spp. have been isolated from many different environmental habitats but have mainly been associated with nosocomial acquired diseases in humans. Although there are many recently published sequenced genomes of members of this genus, there are very few studies on whole genome comparisons between clinical and non-clinical isolates, and it is therefore still an open question if a strain found in nature is capable of infecting humans/animals. Klebsiella michiganensis Kd70 was isolated from the intestine of larvae of Diatraea saccharalis but genome analysis revealed multiple genes associated with colonization and growth promotion in plants suggesting an endophytic lifestyle. Kd70 cells labeled with gfp confirmed capability of root colonization and soil application of Kd70 promoted growth in greenhouse grown sugarcane. Further genomic analysis showed that the Kd70 genome harbored fewer mammalian virulence factors and no pathogen island-like regions when compared to clinical isolates of this species, suggesting attenuated animal/human pathogenicity. This postulation was corroborated by in vivo experiments in which it was demonstrated that Kd70 was unable to infect the mouse urinary tract. This is to the best of our knowledge the first experimental example of a member of a pathogenic Klebsiella spp. unable to infect a mammalian organism. A proteomic comparison deduced from the genomic sequence between Kd70 and several other K. michiganensis strains showed a high similarity with isolates from many different environments including clinical strains, and demonstrated the existence of conserved genetic lineages within this species harboring members from different ecological niches and geographical locations. Furthermore, most genetic differences were found to be associated with genomic islands of clinical isolates, suggesting that evolutionary adaptation of animal pathogenicity to a large extent has depended on horizontal gene transfer. In conclusion our results demonstrate the importance of conducting thorough in vivo pathogenicity studies before presupposing animal/human virulence of non-clinical bacterial isolates.

Maize Combined Insect Resistance Genomic Regions and Their Co-localization With Cell Wall Constituents Revealed by Tissue-Specific QTL Meta-Analyses.

Combinatorial insect attacks on maize leaves, stems, and kernels cause significant yield losses and mycotoxin contaminations. Several small effect quantitative trait loci (QTL) control maize resistance to stem borers and storage pests and are correlated with secondary metabolites. However, efficient use of QTL in molecular breeding requires a synthesis of the available resistance information. In this study, separate meta-analyses of QTL of maize response to stem borers and storage pests feeding on leaves, stems, and kernels along with maize cell wall constituents discovered in these tissues generated 24 leaf (LIR), 42 stem (SIR), and 20 kernel (KIR) insect resistance meta-QTL (MQTL) of a diverse genetic and geographical background. Most of these MQTL involved resistance to several insect species, therefore, generating a significant interest for multiple-insect resistance breeding. Some of the LIR MQTL such as LIR4, 17, and 22 involve resistance to European corn borer, sugarcane borer, and southwestern corn borer. Eleven out of the 42 SIR MQTL related to resistance to European corn borer and Mediterranean corn borer. There KIR MQTL, KIR3, 15, and 16 combined resistance to kernel damage by the maize weevil and the Mediterranean corn borer and could be used in breeding to reduce insect-related post-harvest grain yield loss and field to storage mycotoxin contamination. This meta-analysis corroborates the significant role played by cell wall constituents in maize resistance to insect since the majority of the MQTL contain QTL for members of the hydroxycinnamates group such as p-coumaric acid, ferulic acid, and other diferulates and derivates, and fiber components such as acid detergent fiber, neutral detergent fiber, and lignin. Stem insect resistance MQTL display several co-localization between fiber and hydroxycinnamate components corroborating the hypothesis of cross-linking between these components that provide mechanical resistance to insect attacks. Our results highlight the existence of combined-insect resistance genomic regions in maize and set the basis of multiple-pests resistance breeding.

Within-Host Competition between Two Entomopathogenic Fungi and a Granulovirus in Diatraea saccharalis (Lepidoptera: Crambidae).

We provide insights into how the interactions of two entomopathogenic fungi and a virus play a role in virulence, disease development, and pathogen reproduction for an economically important insect crop pest, the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae). In our model system, we highlight the antagonistic effects of the co-inoculation of Beauveria bassiana and granulovirus (DisaGV) on virulence, compared to their single counterparts. By contrast, combinations of Metarhizium anisopliae and B. bassiana, or M. anisopliae and DisaGV, have resulted in additive effects against the insect. Intriguingly, most cadavers that were derived from dual or triple infections, produced signs/symptoms of only one species after the death of the infected host. In the combination of fungi and DisaGV, there was a trend where a higher proportion of viral infection bearing conspicuous symptoms occurred, except when the larvae were inoculated with M. anisopliae and DisaGV at the two highest inoculum rates. Co-infections with B. bassiana and M. anisopliae did not affect pathogen reproduction, since the sporulation from co-inoculated larvae did not differ from their single counterparts.

Particle Bombardment of the cry2A Gene Cassette Induces Stem Borer Resistance in Sugarcane.

Sugarcane borer is the most common and harmful pest in Chinese sugarcane fields, and can cause damage to the whole plant during the entire growing season. To improve borer resistance in sugarcane, we constructed a plant expression vector pGcry2A0229 with the bar gene as the marker and the cry2A gene as the target, and introduced it into embryogenic calli of most widely cultivated sugarcane cultivar ROC22 by particle bombardment. After screening with phosphinothricin in vitro and Basta spray, 21 resistance-regenerated plants were obtained, and 10 positive transgenic lines harboring the cry2A gene were further confirmed by conventional PCR detection. Real-time quantitative PCR (RT-qPCR) analysis showed that the copy number of the cry2A gene varied among different transgenic lines but did not exceed four copies. Quantitative ELISA analysis showed that there was no linear relationship with copy number but negatively correlated with the percentage of borer-infested plants. The analysis of industrial and agronomic traits showed that the theoretical sugar yields of transgenic lines TR-4 and TR-10 were slightly lower than that of the control in both plant cane and ratoon cane; nevertheless, TR-4 and TR-10 lines exhibited markedly lower in frequency of borer-infested plants in plant cane and in the ratoon cane compared to the control. Our results indicate that the introduction of the cry2A gene via bombardment produces transgenic lines with obviously increased stem borer resistance and comparable sugar yield, providing a practical value in direct commercial cultivation and crossbreeding for ROC22 has been used as the most popular elite genitor in various breeding programs in China.

Management of Field-Evolved Resistance to Bt Maize in Argentina: A Multi-Institutional Approach

Evolution of resistance to control measures in insect populations is a natural process, and management practices are intended to delay or mitigate resistance when it occurs. During the 2012/13 season the first reports of unexpected damage by Diatraea saccharalis on some Bt maize hybrids occurred in the northeast of San Luis province, Argentina. The affected Bt technologies were Herculex I® (HX-TC1507) and VT3PRO® (MON 89034 × MON 88017*). Event TC1507 expresses Cry1F and event MON 89034 expresses Cry1A.105 and Cry2Ab2, whichr are all Bt proteins with activity against the lepidopterans D. saccharalis and Spodoptera frugiperda (MON 88017 expresses the protein Cry3Bb1 for control of coleopteran insects and the enzyme CP4EPSPS for glyphosate tolerance). The affected area is an isolated region surrounded by sierra systems to the northeast and west, with a hot semi-arid climate, long frost-free period, warm winters, hot dry summers, and woody shrubs as native flora. To manage and mitigate the development of resistance, joint actions were taken by the industry, growers and Governmental Agencies. Hybrids expressing Vip3A protein (event MIR162) and/or Cry1Ab protein (events MON 810 and Bt11) as single or stacked events are used in early plantings to control the first generations of D. saccharalis, and in later plantings date's technologies with good control of S. frugiperda. A commitment was made to plant the refuge, and pest damage is monitored. As a result, maize production in the area is sustainable and profitable with yields above the average.

Occurrence of Telenomus dignus (Gahan) on the Sugarcane Borers, Scirpophaga intacta Snellen and Chilo sacchariphagus Bojer in Guangxi Province, China

Sugarcane (Saccharum officinarum L.) is an important crash crop in Guangxi, China. The sugarcane borers (Scirpophaga intacta Snellen and Chilo sacchariphagus Bojer) cause serious damage to sugarcane crop in Guangxi Province. Consequently, increasing attention has been given into the investigation and development of biocontrol agents to control these pests. The parasitoid wasp Telenomus sp. has previously been reported as a natural enemy of sugarcane borers in Guangxi Province. Telenomus dignus is the species found parasitizing borer eggs in field in Fujian Province, but it has not been previously mentioned as natural enemy of these pests. T. dignus was collected on S. intacta egg masses and identified from Shangsi County of Guangxi Province during 2013. In these studies, the parasitic behavior of T. dignus on eggs of S. intacta and C. sacchariphagus was investigated under field conditions during 2013–2014. The results from the current study showed that the percentage of parasitized egg masses of S. intacta parasitized by T. dignus was 45.71 and 57.14% in 2013 and 2014, respectively, while in C. sacchariphagus egg masses, the percentage of parasitism by T. dignus was 45.28 and 51.09% in 2014, respectively. The sex ratio (female/male) of T. dignus adults on S. intacta was 1.45:1 in 2013 and 5.17:1 in 2014 and was 2.17:1 on C. sacchariphagus in 2014. T. dignus was the dominant egg parasitoid of these two species of sugarcane borers in isolated sugarcane regions in Guangxi Province. Further investigations on biology of T. dignus are required to develop this parasitoid as a more widespread biocontrol agent of sugarcane borers.

Lack of Detection of Bt Sugarcane Cry1Ab and NptII DNA and Proteins in Sugarcane Processing Products Including Raw Sugar.

Brazil is the largest sugarcane producer and the main sugar exporter in the world. The industrial processes applied by Brazilian mills are very efficient in producing highly purified sugar and ethanol. Literature presents evidence of lack of DNA/protein in these products, regardless of the nature of sugarcane used as raw material. Recently CTNBio, the Brazilian biosafety authority, has approved the first biotechnology-derived sugarcane variety for cultivation, event CTC175-A, which expresses the Cry1Ab protein to control the sugarcane borer (Diatraea saccharalis). The event also expresses neomycin-phosphotransferase type II (NptII) protein used as selectable marker during the transformation process. Because of the high purity of sugar and ethanol produced from genetically modified sugarcane, these end-products should potentially be classified as “pure substances, chemically defined,” by Brazilian Biosafety Law No. 11.105. If this classification is to be adopted, these substances are not considered as “GMO derivatives” and fall out of the scope of Law No. 11.105. In order to assess sugar composition and quality, we evaluate Cry1Ab and NptII expression in several sugarcane tissues and in several fractions from laboratory-scale processing of event CTC175-A for the presence of these heterologous proteins as well as for the presence of traces of recombinant DNA. The results of these studies show that CTC175-A presents high expression of Cry1Ab in leaves and barely detectable expression of heterologous proteins in stalks. We also evaluated the presence of ribulose-1,5-bisphosphate carboxylase/oxygenase protein and DNA in the fractions of the industrial processing of conventional Brazilian sugarcane cultivars. Results from both laboratory and industrial processing were concordant, demonstrating that DNA and protein are not detected in the clarified juice and downstream processed fractions, including ethanol and raw sugar, indicating that protein and DNA are removed and/or degraded during processing. In conclusion, the processing of conventional sugarcane and CTC175-A Bt event results in downstream products with no detectable concentrations of heterologous DNA or new protein. These results help in the classification of sugar and ethanol derived from CTC175-A event as pure, chemically defined substances in Brazil and may relieve regulatory burdens in countries that import Brazilian sugar.

Development of Transgenic Sugarcane Resistant to Sugarcane Borer

Sugarcane borer (Diatraea saccharalis) is a major pest of sugarcane (Saccharum spp. hybrids), across the Americas. The insect is partially controlled by biological and chemical means, but still causes significant economic losses to sugarcane growers and processors. Proteins derived from Bacillus thuringiensis, Bt proteins, have been used to control sugarcane borer in maize (Zea mays) for the past decade. In sugarcane, the expression of individual Bt proteins has been reported several times. However practical use of Bt proteins requires their use as part of an Integrated Pest Management (IPM) system that includes the delivery of high doses of protein and the use of a refuge to slow the evolution of insect resistance to the protein. Here we demonstrate the feasibility of using Bt proteins to protect sugarcane from sugarcane borer in a commercial setting. We have expressed two Bt proteins with differing modes of action (Cry1Ab and Cry2Ab) in commercial sugarcane varieties, demonstrated efficacy against sugarcane borer in the field and describe a strategy for trait deployment in this tropical crop with complex genetics that limits trait introgression by backcrossing.

Alternative to formaldehyde in artificial diet for sugarcane borer and its effects on the parasitoid

The formaldehyde used as anti-contaminant agent in artificial diets of insects can cause serious risks to human health. However, there are products with the same purpose, but with less toxicity to humans. In this sense, the aim of this study was to evaluate the biological parameters of Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) fed on an artificial diet containing different anti-infective agents to replace the formaldehyde, as well as analyze the effects on its parasitoid Cotesia flavipes (Cameron, 1891) (Hymenoptera: Braconidae). The experiment was conducted under a completely randomized design, studying the anti-contaminant agents: sodium benzoate, potassium sorbate, 2-phenylphenol, and formaldehyde (standard diet), with deionized water as control. The larvae of sugarcane borer were fed on diets with the cited agents, and were daily observed for: larval and pupal periods, larval and pupal viabilities, number of unviable larvae, longevity, pupae weight, sex ratio and the adults fecundity. To analyze the effects of the anti-contaminant agents on the C. flavipes parasitoid, 50 larvae of sugarcane borer were parasitized and daily observed until the parasitoid pupae formation, being evaluated: number of adults emerged per pupal mass, longevity and sex ratio. D. saccharalis larvae are positively influenced by replacing formaldehyde to 2-phenylphenol in their diet, not causing significant deleterious effects to C. flavipes.

Field-evolved resistance to Bt maize in sugarcane borer (Diatraea saccharalis) in Argentina.

BACKGROUNDMaize technologies expressing Bacillus thuringiensis (Bt) insecticidal proteins are widely used in Argentina to control sugarcane borer (Diatraea saccharalis Fabricius). Unexpected D. saccharalis damage was observed to Bt maize events TC1507 (expressing Cry1F) and MON 89034 × MON 88017 (expressing Cry1A.105 and Cry2Ab2) in an isolated area of San Luis Province. Diatraea saccharalis larvae were sampled from MON 89034 × MON 88017 fields in the area to generate a resistant strain (RR), which was subsequently characterized in plant and diet bioassays.RESULTSSurvivorship of the RR strain was high on TC1507 leaf tissue, intermediate on MON 89034 × MON 88017, and low on MON 810 (expressing Cry1Ab). The RR strain had high resistance to Cry1A.105 (186.74‐fold) and no resistance to Cry2Ab2 in diet bioassays. These results indicate resistance to Cry1F and Cry1A.105 (and likely cross‐resistance between them) but not to Cry1Ab or Cry2Ab2. Resistance to MON 89034 × MON 88017 was functionally recessive. Reviews of grower records suggest that resistance initially evolved to Cry1F, conferring cross‐resistance to Cry1A.105, with low refuge compliance as the primary cause. A mitigation plan was implemented in San Luis that included technology rotation, field monitoring, and grower education on best management practices (BMPs) including refuges.CONCLUSIONIn the affected area, the resistance to Cry1F and Cry1A.105 is being managed effectively through use of MON 89034 × MON 88017 and MON 810 in combination with BMPs, and no spread of resistance to other regions has been observed. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Use of Cotesia for the Control of Sugarcane Drill

Sugarcane plays an important role for Brazil’s economy. However, crop infestation such as the common bed borer is still a major challenge for companies and farmers. Previous studies have shown that Cotesia, a living product, may be effective in combating sugarcane borer. In order to verify the relevance of the use of Cotesia in control of sugarcane borer, the method on infestation prevention, high quality sugarcane preservation and harvesting was optimized in this study. This study confirmed that biological control is effective than that of chemical control but with great viability.

Sugarcane Borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), Injury and Survival in Energy Cane Versus Sugarcane

Energy cane and sugarcane are genetically similar, but due to differences in plant growth, morphology and fiber content, it is important to understand sugarcane borer, Diatraea saccharalis (F.), feeding injury and survival in energy cane cultivars versus sugarcane cultivars. In this study, free-choice and no-choice tests were conducted with sugarcane borer larvae on energy cane (UFCP 78-1013, UFCP 82-1655, UFCP 84-1047) and sugarcane (CP 88-1762, CP 89-2143, CP 00-1101) cultivars. Overall, the feeding preference and injury varied more in individual cultivars than a trend in energy cane versus sugarcane. In free-choice test, small larvae preferred UFCP 82-1655 leaves more than two sugarcane cultivars (CP 89-2143 and CP 00-1101) for feeding. There was no feeding preference in large larvae for the stalks. In no-choice tests, weight gain in small larvae and number of holes bored by large larvae were lowest in energy cane cultivar UFCP 84-1047 and highest in sugarcane cultivar CP 88-1762, with no difference in other cultivars. Lower stalk injury in UFCP 84-1047 in no-choice test was probably due to its greater stalk rind hardness than sugarcane as well as other energy cane cultivars. Sugarcane borer survival was similar in all the cultivars. Our results show that energy cane is a host for sugarcane borer but injury varies with cultivar and hence cultivar selection may play an important role in developing sugarcane borer management strategies in energy cane. Further research will be needed to evaluate energy cane response to sugarcane borer infestation under field conditions.

Assessing resistance of sugarcane varieties to sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae).

In this study, we investigated resistance traits to the sugarcane borer Diatraea saccharalis Fab. (Lepidoptera: Crambidae) in the leaves and stalks of six sugarcane cultivars in a series of greenhouse and laboratory assays. Investigation of plant factors and infestation rates to better discriminate stalk damage by the sugarcane borer indicated that infestation of 7-month-old, single plants with 20 larvae at the third or fourth instar per plant was suitable to assess tunneling length. Three cultivars (i.e. SP803280, RB928064, and RB835486) had lower stalk damage (i.e. tunnel length) than cultivar SP891115, which exhibited relatively greater susceptibility to tunneling by the borer. The time required for the larvae to enter the sugarcane stalk was longer for cultivar SP803280, indicating resistance traits on the stalk surface, which correlated with lower stalk damage. Larvae feeding on SP813250 stalks had the lowest weight gain, indicating that this cultivar has resistance traits to larval development within its stalks. Cultivars RB867515 and SP891115 resulted in the highest mortality of early-stage larvae feeding on leaves, indicating the presence of resistance factors in their leaves. Multi-trait cluster and principal component analyses placed the cultivars into three and four clusters, respectively. The cultivars placed in different groups that exhibited resistance to leaf feeding, stalk entrance, and tunneling by the sugarcane borer could be used for crossings in sugarcane breeding programs with the goal of obtaining higher levels of resistance to D. saccharalis.

Yield, Quality and Natural Infestation with Insect and Disease of Four Sugarcane Varieties as Affected by Different Levels of Potassium Fertilization

The present experiments were carried out in El-Mattana Research Station (latitude of 25.25°N and longitude of 32.31°E), AgriculturalResearchCenter, Luxor Governorate, Egypt. The present work was conducted on two plant cane crops grown in 2015/2016 and 2016/2017 seasons to study the yield, quality and natural of infestation with lesser sugarcane borer, Chilo agamemnon Bles., and pokkah boeng disease (Fusarium moniliforme Sheldon) and other diseases of four sugarcane varieties (G.T.54-9, G.2003-47, Ph 8013 and C. 57-14) as affected by three levels of potassium fertilization (zero, 24 and 48 kg K2O/fed.). The results showed that the difference in mostly traits between sugarcane variety G.T.54-9 and G.2003-47 was insignificant, they surpassed the other two varieties in number of millable canes and cane and sugar yield/fed. Also, they recorded the highest percentages of infestation with C. agamemnon Bles., and pokkah boeng, during the two successive seasons. The sugarcane variety Ph 8013 showed significant superiority in stalk weight, sucrose% and sugar recovery%. However, the variance between the two sugarcane varieties namely Ph 8013 and G.2003-47 in sucrose% and sugar recovery% was insignificant. Increasing the applied dose of potassium fertilizer up to 48 kg K2O/fed. was accompanied by a significant increase in the values of number of millable canes, stalk weight/plant and sugar yields as well as decreased of percentage of infestation with C. agamemnon Bles., and pokkah boeng disease, during the two successive seasons. However, the variance between 24 and 48 K2O/fed. in sucrose%, sugar recovery% and cane yields/fed. was insignificant during the two successive seasons. Fertilizing sugar cane crop by 24 and 48 kg K2O/fed. increased cane yield by 6.47 % & 7.51 % during the first season and 4.51 % & 11.34 % during the second season, respectively, compared with check treatment.

Increased tolerance of Beauveria bassiana and Metarhizium anisopliae conidia to high temperature provided by oil-based formulations.

The influence of the temperature of aqueous conidial sprays on conidial viability and virulence against Diatraea saccharalis was evaluated for pure conidia, rice + fungus (technical concentrates) and oil-based formulations of Beauveria bassiana s.s. and Metarhizium anisopliae s.s. under laboratory conditions. The fungal preparations were suspended in water and maintained at 26 °C, 36 °C and 46 °C for one, four and six hours. Conidial viability was determined by plating aliquots of each suspension onto PDA medium followed by incubation for 20-22 h and observing for viable conidia (germ tubes longer than diameter of conidia). Fungal virulence was determined by spraying suspensions onto third-instar larvae of D. saccharalis. In general, germination and virulence, particularly for unformulated conidia, were negatively affected by increases in water temperature and exposure time in suspension. However, the decrease in conidial viability in the oil-in-water emulsion was less than 7% for both species after 6 h of exposure at 36 °C, in contrast to reductions of 7-21% and 28-60% for the oil-free suspensions of B. bassiana and M. anisopliae, respectively. For the sprays of conidia in an oil-in-water emulsion previously exposed to elevated water temperatures for longer periods, the levels of insect mortality were higher than those of pure conidia or technical concentrates under identical conditions. Our results indicate that emulsifiable oil-based formulations can protect the conidia of both species of fungi from the adverse effects of high water temperatures before spraying in the field.