Diatraea Species Research Articles

Development of a bioassay method to test activity of cry insecticidal proteins against Diatraea spp. (Lepidoptera: Crambidae) sugarcane stem borers.

The genus Diatraea (Lepidoptera: Crambidae) includes stem borers representing the most critical sugarcane pests in the Americas. Colombia's most widely distributed and damaging Diatraea species include Diatraea saccharalis, D. indigenella, D. busckella, and D. tabernella. The reduced efficacy of biological tools commonly used in controlling several species highlights the importance of evaluating alternative management strategies, such as transgenic plants expressing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). The selection of optimal Bt insecticidal proteins for Diatraea control depends on bioassays with purified Bt proteins. Because there is no described artificial diet for borer species other than D. saccharalis and availability of most purified Bt toxins is restricted, this study aimed at developing a bioassay method using fresh corn tissue and providing proof of concept by testing susceptibility to the Cry1Ac insecticidal protein from Bt. Toxicity was evaluated with a single Cry1Ac dose applied directly to corn discs. Stem borer mortality after seven days was higher than 90% for all four tested Diatraea species, while control mortality was below 8%. In addition, we observed that Cry1Ac caused more than 90% weight inhibition in all survivors and delayed development. These results validate the use of this method to determine mortality and growth inhibition due to the consumption of the Cry1Ac protein in each of the Diatraea species. Furthermore, this method could be used to assess other entomopathogenic substances to control these insect pests.

Divergent life histories between wild and commercially-sourced Cotesia flavipes (Hymenoptera: Braconidae) parasitizing four species of Diatraea (Lepidoptera: Crambidae)

Moths of the genus Diatraea Guilding (Lepidoptera: Crambidae) are stalk-boring pests of sugarcane throughout the neotropics. In Colombia, the economically important species are D. busckella, D. indigenella, D. saccharalis, and D. tabernella. Augmentative releases of the gregarious endoparasitoid Cotesia flavipes (Cameron) are one tactic used to manage this pest complex. We compared the laboratory performance of two C. flavipes populations, one field-collected, and one commercially-sourced, on all four host species, hypothesizing lower performance of the commercial population on host species other than D. saccharalis due to continuous rearing on this species. Parasitism success did not vary with parasitoid source, but varied among host species, being highest in D. indigenella and lowest in D. tabernella, with other species intermediate. Sex ratio was female-biased, averaging 0.635, and did not vary with parasitoid source or host species. Wild wasps developed more slowly than commercial wasps on all hosts, being slowest on D. tabernella, whereas commercial wasps were slowest on D. busckella. Both parasitoid populations produced their largest broods in D. indigenella, but commercial wasps produced smaller broods than wild wasps in D. busckella and D. tabernella, and substantially lower weight gain of host larvae post-parasitism, suggesting impaired host regulation ability. In all host species, wild wasps produced larger female progeny, based on wing area, than commercial wasps. When all metrics of parasitoid performance (fitness) were combined into a single index of host suitability, D. indigenella was the most suitable host for both parasitoid populations. Both parasitoid sources had similar performance on D. saccharalis, the host used to rear the commercial population, whereas wild wasps performed better on all other Diatraea species. The inadvertant consequences of artificial selection in mass-reared cultures of gregarious endoparasitoids are discussed, specifically the evolution of faster development and smaller body size.

Biology and life cycle Of Diatraea busckella (Lepidoptera: Crambidae) under simulated altitudinal profile in controlled conditions

Abstract Diatraea busckella (Lepidoptera: Crambidae), a sugarcane borer, was recently reported in Valle del Cauca, Caldas, and Risaralda in Colombia. This fact puts sugarcane (S. officinarum) producers in a critical situation. The insufficient knowledge about Diatraea species phenomenology, biology, and the life cycle feature under different climate scenarios does not let the experts relate (with certainty) the population explosion with climate offer changes. The work was carried out at the Center for Research and Breeding of Natural Enemies, located in the botanical garden of the University of Caldas at 5.0563885°3′23″ north latitude and −75.49416675°29′39″ west longitude, at an altitude of 2,160 m above the sea level and an average temperature of 14°C (Manizales, Caldas). To cope with the lack of bio-meteorological information, an experimental approach, based on the simulation of sugar cane production environments, was designed for obtaining the relationship between air temperature and the life cycle of the sugarcane borer. Growth chambers were used to simulate the air temperature of five ambients (10, 20, 24.7, 30, and 35°C). Under low latitude conditions (5°N), the referred temperatures corresponded to x, y, z, a, and b. The cycles were completed up to the first oviposition by females; in addition, the direct relationship between air temperature and the insect’s development, reproduction, and survival was verified. The number of days of the larval stage was 40 days DS ± 16.7 ± 2 days from larva to pupae and 6 ± 1 more to reach the adult stage under controlled conditions under five different temperatures (10, 20, 24.7, 30, and 35°C). In addition, significant differences were found in development time under controlled conditions (20, 24.7, and 30°C). Diatraea busckella can become a significant pest due to the positive response in development when environmental scenarios have to change, specifically the increase in temperature.

Improving ecological fitness of Beauveria bassiana conidia to control the sugar cane borer Diatraea saccharalis

ABSTRACTDiatraea species are considered the most important insect pests in sugarcane crops in Colombia and other South America countries. Previous research demonstrated Beauveria bassiana isolate Bv062 to be pathogenic to larvae of Diatraea species under laboratory conditions. However, virulence of the isolate was variable, possibly affected by inoculum quality. The aim of this research was to select an appropriate mass culture medium to produce conidia with consistently high yield, high virulence, and high storage stability. Conidia were produced on three semi-solid media based on rice, oat and potato, which were adjusted to three levels of water activity (aw). Conidia yield, germination, polyols accumulation, enzymatic activity, and virulence to Diatraea saccharalis larvae, before and after 30 days of storage at 30°C, were measured. Conidia produced on potato-based medium were the most virulent, with a median lethal time (LT50) of 8.9 days, compared to 9.7 and 9.1 days for rice and oat media, respectively. Insecticidal activity was stable after one month of storage for conidia produced on potato (LT50 8.0 days) but was reduced for conidia produced on the other media (LT50 13.0 days and 11.7 days for rice and oat, respectively). Mannitol was the predominant polyol in conidia and trehalose was not detected. Maximum yield and storage stability were obtained in the potato-based medium (C:N ratio of 30:1). Based on these results, potato-based medium is superior to the standard rice-based medium for the production of B. bassiana Bv062 conidia with better ecophysiological performance to control the sugar cane borer.

The gregarious parasitoid Cotesia flavipes displays a high level of preadaptation to a novel host, Diatraea indigenella

Cotesia flavipes Cameron (Hymenoptera: Braconidae) is often augmented against Diatraea spp. (Lepidoptera: Crambidae) stem borers in the Americas. Diatraea indigenella Dyar and Heinrich, an endemic pest of sugarcane in southern Colombia, represents a novel host for C. flavipes. We examined the development of C. flavipes on D. indigenella and D. saccharalis, a familiar host, when larvae were stung by one, two or three wasps. Host species had no effect on parasitism success, immature parasitoid mortality, parasitoid developmental time, adult emergence, or female size. Superparasitized D. indigenella hosts yielded more cocoons, more adults, and more female wasps than those parasitized with a single sting, or from D. saccharalis hosts. However, wasp survival and longevity declined when host larvae were stung three times. Thus, D. indigenella was a more suitable host for C. flavipes when superparasitized, and appears suitable for augmentation against this emergent pest and other Diatraea species attacking sugarcane.

Host resistance to two parasitoids (Diptera: Tachinidae) helps explain a regional outbreak of novel Diatraea spp. stem borers (Lepidoptera: Crambidae) in Colombia sugarcane

Lydella minense and Billaea claripalpis (Diptera: Tachinidae) are important parasitoids used in augmentation biological control of sugarcane stem borers, Diatraea spp. (Lepidoptera: Crambidae), the primary pests of sugarcane in Colombia. Following the recent discovery of two new Diatraea species in the Cauca River Valley (CRV), D. tabernella and D. busckella, stalk-boring damage to sugarcane has increased and rates of larval parasitism have declined. The present study assessed the suitability of all four stalk-boring Diatraea species now present in the CRV, D. tabernella, D. busckella, D. indigenella and D. saccharalis, as hosts for the two parasitoids. Following manual inoculation of larvae with maggots of L. minense and B. claripalpis, the development, immature survival, sex ratio and longevity of resulting flies were recorded. Both parasitoid species parasitized a lower percentage of D. tabernella and D. busckella larvae compared to larvae of D. saccharalis or D. indigenella. Although host larvae were more likely to yield two puparia of L. minense than of B. claripalpis, the likelihood of a second puparium was reduced when L. minense parasitized D. tabernella and D. busckella. These results suggest these two Diatraea species have resistance to parasitism by the tachinids, which might explain why outbreaks of these pests have occurred in the regions of the CRV where commercial releases of the parasitoids are relied upon as the primary pest management tactic. Although breeding programs may eventually provide flies with improved ability to parasitize these novel host species, additional work is warranted to explore alternative pest management tactics for these stem borers.

Cotesia flavipes(Hymenoptera: Braconidae) as a Biological Control Agent of Sugarcane Stem Borers in Colombia's Cauca River Valley

Releases of the parasitoid Cotesia flavipes have been carried out since late 2014 in Colombia's Cauca River Valley to complement other biological control on sugarcane stem borers (Diatraea spp.). To confirm the identity of the species being released as well as those recovered in the field, including samples from the department of Santander in western Colombia, specimens were examined using a fragment of cytocrome oxydase I (COI). Results confirmed that the genetic identity of the specimens sequenced corresponded to C. flavipes, with a genetic divergence of 0.00 to 0.03 as compared with GenBank registers. In the Cauca River Valley, parasitoid distribution currently extends from La Virginia (Risaralda) to Palmira (Valle del Cauca), and is mainly associated to the geographical distribution of the new Diatraea species reported in the region, D. busckella and D. tabernella.

Morphological and molecular characterization of Brazilian populations of Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) and the evolutionary relationship among species of Diatraea Guilding.

The sugarcane borer or corn stalk borer, Diatraea Guilding is polyphagous insect pest of many important crops such as corn, sorghum and sugarcane. Losses arising from the attack of Diatraea species have been a serious problem, which may cause loss in sugarcane production around 0.25% in sugar, 0.20% in alcohol and 0.77% of body weight for every 1% infestation and up to 21% in corn production fields. In Brazil, the most commonly reported species are Diatraea saccharalis (Fabricius, 1794) and Diatraea impersonatella (Walker, 1863) (= D. flavipennella). However, multiple other species of Diatraea have been identified in Brazil according to the literature. Currently, little information exists on the presence of the other species causing injury to sugarcane and corn. The objectives of this study were to improve the accuracy of species assignment, evaluate the population genetic structure, and address many of the outstanding questions of systematics and evolution of Brazilian populations of D. saccharalis. To address these main questions, classical taxonomic methods were used, focused on morphological characterization of the reproductive organs, especially the male genitalia. In addition, genetic studies were performed using simple sequence repeats (SSR) and a fragment of cytochrome C oxidase subunit I (COI) gene. The data and findings from this research will contribute to the understanding of evolutionary aspects of insect pests in order to develop more effective and sustainable population management practices.

The Diatraea Complex (Lepidoptera: Crambidae) in Colombia's Cauca River Valley: Making a Case for the Geographically Localized Approach.

The sugarcane stem borers Diatraea saccharalis (Fabricius) and D. indigenella Dyar & Heinrich are common pests of sugarcane crops in Colombia's Cauca river valley (CRV). In 2012, however, D. tabernella Dyar was recorded for the first time in northern CRV and just 1year later, D. busckella Dyar & Heinrich was detected, also for the first time, in central CRV. The Diatraea outbreak in the CRV was studied, its distribution and population in the region was analyzed, and levels of larval parasitism were observed. During the study of the outbreak, Diatraea species in the CRV were characterized based on the morphology of larval, pupal, and adult stages. Keys to the identification of Diatraea in the CRV based on male genitalia and pupa are provided. Pupal cephalic horns and lateral lobes were discovered as new, reliable characteristics to separate the species at the pupal stage. We suggest biological control program modifications to decrease economic impact and studies at geographically localized levels to better understand the dynamics between the pest species and their parasitoids.

Identification of Diatraea spp. (Lepidoptera: Crambidae) based on cytochrome oxidase II.

Diatraea spp. (Lepidoptera: Crambidae) are a group of insects that are agriculture pests in many economically relevant crops such as sugarcane, sorghum, corn and rice. Recognized species for this genus respond differentially to natural enemies used in their biological control, emphasizing the importance of species in a regional approach. Currently, identification is based on the male genitalia. However, the availability of specimens collected from field and subjectivity based on the character recognition can seriously hamper species identification, and therefore result in inadequate pest management. To overcome this, individuals of Diatraea spp. preliminarily classified male genitalia and obtained from reared conditions and the field (both derived from natural populations occurring in Colombia) were analyzed using genitalic morphometry and molecular biology specifically using a fragment of the cytochrome oxidase subunit II (CO II) mitochondrial gene. Although morphometric analysis did not show any overriding results regarding genitalia morphology, the bioinformatics analyses of CO II sequences resulted in an adequate classification of the individuals within the recognized species. It also, revealed that the occurrence of clades associated with geographical distribution may be associated with cryptic species. The latter was also confirmed by a Single-Strand Conformation Polymorphism (SSCP) methodology evaluating the same fragment of CO II. This experimental approach allows properly recognizing each species and in consequence is proposed as an effective tool in Diatraea species identification.

ITS2 as a molecular marker for the identification of Diatraea saccharalis and D. flavipennella and possible infection with Cotesia spp.

In Brazil, the species Diatraea flavipennella and D. saccharalis play an important role in the sugar and alcohol agribusiness by causing many damages in sugarcane fields. The egg, larva, pupa, and adult stages are very morphologically similar between these species, and the identification can be confused. The internal transcribed spacer 2 (ITS 2) from ribosomal DNA has important features as evolutionary divergence. It is a good marker for species identification, participates in the rDNA processing, and has been applied in phylogenetic and population studies. This study aimed to make available a molecular marker to assist on the identification method of pests' species of Diatraea and to identify possible traces of Cotesia in the resistant host. The DNA was extracted from the egg, larva, and adult samples. PCR amplicons were purified and sequenced. The sequences were analyzed in MEGA 5.01. The ITS 2 length was 410 bp in D. flavipennella and 448 bp in D. saccharalis. The GC content was similar between the species. Three microsatellite loci were present in D. saccharalis and absent in D. flavipennella, contributing to differences in ITS 2 length in the species. An additional 367-bp band was attributed to Cotesia spp. The differences among ITS 2 from D. flavipennella, D. saccharalis, and Cotesia sp were sufficient to identify them on electrophoresis gel and sequencing. The presence of Cotesia sp traits in adult D. flavipennella showed possible host refractoriness, but further studies are necessary.

Species of Stalk Borers (Lepidoptera: Crambidae) and Damage to Maize in Southeastern Mexico

Abstract. Stalk borers (Diatraea spp.) are important pests of maize, Zea mays L., in the Neotropical region. The objective of this research was to identify the Diatraea species and assess the injury they cause and their effect on yield of maize at Tabasco, Mexico. In total, 199 larvae and 54 pupae were found infesting 319 (62.4%) of 511 plants sampled. Species analyses showed 97.6% were Diatraea lineolata (Dyar) and 2.4% D. saccharalis (F). Despite the great amount of injury, no significant difference between yield and the number of nodes injured per plant was observed (R2 = 0.014, P > 0.05). This is the first report of corn borers injuring maize in this area, and the findings suggest economic damage does not occur when stalk injury is <63% and maize matures before the borers complete development.

Sugarcane Stem Borers of the Colombian Cauca River Valley: Current Pest Status, Biology, and Control

Sugarcane stem borers of the genus of Diatraea (Lepidoptera: Crambidae) form a species complex that causes serious economic losses to sugarcane production in the Cauca River Valley and other regions of Colombia. Two primary species, Diatraea saccharalis (F.) and D. indigenella Dyar and Heinrich, have been effectively managed for more than 4 decades through augmentative releases of the tachinid flies Lydella minense (Townsend) and Billaea claripalpis (Wulp) (Diptera: Tachinidae) and the egg parasitoid Trichogramma exiguum Pinto & Platner (Hymenoptera: Trichogrammatidae). Here we review the current pest status of Diatraea species, damage assessment protocols, management tactics, and the environmental factors and cultural practices that can affect biological control outcomes. Recent changes in the cultivars grown have the potential to increase pest populations and diminish biological control efficacy. Additionally, recent outbreaks of new Diatraea species may further increase overall pest pressure. Thus, there is a need to develop supplementary tactics for the management of these pests that will be compatible with biological control, as well as more reliable protocols for assessing host plant resistance against the increase in infestation intensity.

First Record ofDiatraea tabernella(Lepidoptera: Crambidae) in the Caucariver Valley of Colombia

SUMMARY Diatraea tabernella is recorded for the first time in the Cauca River Valley of Colombia. Even though there has been no information on the status of D. tabernella in Colombia for almost a century, its recent appearance creates concern about its potential economic importance by virtue of its abundance and distribution in the northern region of the Cauca River Valley. Descriptions of the pupae and the male genitalia of D. saccharalis, D. indigenella, and D. tabernella are given, together with a key to aid in the identification of Diatraea species in the region. Also information and perspectives on biological control of D. tabernella are presented.

Preference of the parasitoid Cotesia flavipes (Cam.) (Hymenoptera: Braconidae) for Diatraea (Lepidoptera: Crambidae)

The sugarcane borer Diatraea flavipennella (Box.) (Lepidoptera: Crambidae), has ultimately predominated in the sugarcane fields of the Brazilian northeast region, despite the continual release of the parasitoid Cotesia flavipes (Cam.) (Hymenoptera: Braconidae). Questions have been raised about the efficiency of Diatraea spp. in controlling D. flavipennella. In this study, females reared in one of the borers were tested individually and as hosts with the larvae of either of the Diatraea species alone or the larvae of both species. In the first experiment, the females were released for 10 min within the experimental arena using only olfactory cues. In the second experiment, C. flavipes females were individually released for 30 min. within the arena, allowing direct contact with its host, either D. saccharalis or D. flavipennella, or both host species at the same time. The wasps showed no preference for either one of the hosts, thus being able to locate borers in general.

Influence ofSaccharum officinarum(Poales: Poaceae) Variety on the Reproductive Behavior ofDiatraea flavipennella(Lepidoptera: Crambidae) and on the Attraction of the ParasitoidCotesia flavipes(Hymenoptera: Braconidae)

The aims of this laboratory-based study were: (1) to elucidate the reproductive behavior of Diatraea flavipennella Box in the presence of different sugarcane varieties, (2) to evaluate the capacities of Cotesia flavipes Cameron parasitoids raised on Diatraea saccharalis Fabricius and D. flavipennella to search for healthy and D. flavipennella-infested sugarcane varieties, and (3) to assess the response of the parasitoids towards volatiles released by healthy and D. flavipennella-infestea sugarcane plants. There were no significant differences (P ≥ 0.05) in calling, courtship, and copulation activities when D. flavipennella females, males, or couples were exposed to different sugarcane varieties. According to the number of egg masses and the total number of eggs oviposited, D. flavipennella females showed no preference for any sugarcane variety. The attraction of C. flavipes females to infested plants was significantly greater (P < 0.001) than to healthy plants, independent of the species of Diatraea on which the parasitoids had been reared. The number C. flavipes attracted to volatiles from infested sugarcane plants was significantly greater than those attracted to volatiles from healthy plants or to a hexane control (P < 0.001). It is concluded that none of the sugarcane varieties influenced the reproductive behavior of D. flavipennella, although the state of infestation of the host plants strongly influenced the response of C. flavipes.

Competition of Bacillus thuringiensis Cry1 toxins for midgut binding sites: a basis for the development and management of transgenic tropical maize resistant to several stemborers.

Binding and competition of five Bacillus thuringiensis toxins--Cry1Ab, Cry1Ac, Cry1Ba, Cry1Ca, and Cry1Ea--for midgut binding sites from three pests, Spodoptera frugiperda, Diatraea saccharalis, and Diatraea grandiosella, were investigated as part of a strategy to develop tropical transgenic maize resistant to several stemborers. On S. frugiperda, Cry1Ab and Cry1Ac compete for the same binding site; Cry1Ba and Cry1Ca compete for a second binding site. Cry1Ea recognizes a third specific binding site in S. frugiperda and does not compete with any of the other toxins. On D. grandiosella and D. saccharalis, Cry1Ac competes with Cry1Ab and not with Cry1Ba and Cry1Ca. Cry1Ba and Cry1Ca recognize each a specific binding site and do not compete with any of the other four toxins. Cry1Ea does not recognize any binding site on Diatraea species. Combinations of toxins are proposed to develop transgenic maize resistant to the three stemborers while allowing resistance management.

Encapsulation and hemocyte numbers in three lepidopteran stemborers parasitized by Cotesia flavipes‐complex endoparasitoids

AbstractDetermination of the potential and actual host range of a natural enemy is crucial before its importation and release for biological control. We studied some of the factors that are important in determining the physiological host range of insect parasitoids attacking lepidopteran hosts. Our experimental system consisted of novel host‐parasitoid associations, with two New World pyralid stalk borers, Diatraea saccharalis and D. grandiosella; one Old World crambid borer, Ostrinia nubilalis as hosts; and three Old World microgastrine braconids, Cotesia chilonis, C. sesamiae, and C. flavipes as parasitoids. Experiments on the chronology of encapsulation of the parasitoid progeny by host hemocytes indicated that lepidopteran stemborers that are taxonomically, behaviorally and ecologically very similar differ in their ability to encapsulate a parasitoid species. D. saccharalis encapsulated C. flavipes sometimes, whereas D. grandiosella consistently encapsulated C. sesamiae and C. flavipes. C. chilonis was not encapsulated by either Diatraea host. If encapsulation occurred it did not start until four days after parasitization and continued during the following days. O. nubilalis was an unsuitable host for all three parasitoid species; parasitoid eggs were killed within 24 hours of parasitization. O. nubilalis had nearly twice as many hemocytes present in the hemolymph compared to the Diatraea species. In many of the host‐parasitoid combinations, there was an initial increase of hemocyte number soon after parasitization, which was not due to mechanical damage at oviposition. There was no correlation between total numbers of hemocytes present in the host hemolymph and the observed encapsulation levels. By understanding the encapsulation response we may be able to make better predictions about the host range of a parasitoid species before its release as a biological control agent.

Two new species of Digonogastra Viereck (Hymenoptera: Braconidae) parasitic on Neotropical pyralid borers (Lepidoptera) in maize, sorghum and surgane

AbstractDigonogastra kimballi sp. n. and D. solitaria Wharton &amp; Quicke sp. n. are described from Texas and Mexico. They attack stalk-boring pyralids in a variety of gramineous plants, including maize, sorghum and sugarcane. Known hosts are Eoreuma loftini (Dyar) and five species of Diatraea.

A new genus and species of Braconinae (Hymenoptera: Braconidae) parasitic on Diatraea sp. (Lepidoptera: Pyralidae) from Ecuador

AbstractThe braconine Palabracon diatraeaphilus gen. et sp. n. is described and illustrated from a unique female collected in Ecuador. The new species was reared as a parasitoid of an undetermined species of Diatraea.