Entomology Webinar

Programme

Introduction by Julien Beuzelin, Chair ISSCT Entomology Section

• From Endemic to Exotic Pests of Sugarcane – Preparing for the Unexpected. Kevin Powell, Sugar Research Australia, Meringa, Queensland, Australia

Abstract: The Australian sugarcane industries major insect pests are the canegrubs, comprising 20 species. Most of the species are endemic and have been controlled primarily using insecticides. However, the industry relies solely on the use of a single neonicotinoid, imidacloprid, for control of the larvae. This product has been used for two decades and has been very successful. However, neonicotinoids are under scrutiny and other alternatives including biorationals are being explored. Screening of such alternatives needs to occur to provide sufficient scientific evidence of efficacy, persistence and reduced environmental consequences. In Australia, a new 4-year research project is currently focusing on developing rapid in situ and in field screening methods to improve the selection of sustainable alternatives to imidacloprid.

In 2012 a newly described cane disorder called Yellow Canopy Syndrome (YCS) was described from Cairns in Far North Queensland. Despite multiple research projects the direct cause of YCS has yet to be determined. However, there is increasing evidence, most notably from both insecticide and variety trials, that invertebrates are likely to be involved in YCS expression. Recent studies on YCS have utilised novel and existing sampling procedures to determine which invertebrates are likely to be involved and how climatic conditions impact their abundance. These studies have highlighted for the first time not only potential invertebrates involved in YCS but also the diversity of invertebrates present in the sugarcane ecosystem. Some of the effective monitoring methods developed will be utilised to ensure that future management approaches are utilised only as and when required.

With the exception of canegrubs, the Australian Sugarcane industry has relatively few endemic pests of economic significance but due to its close proximity to other cane growing countries is at risk of exotic pest incursions through either wind dispersal or movement of infested plant material. Strict biosecurity regulations and regular monitoring in Far North Queensland have so far limited this risk. However, the fall armyworm (FAW), Spodoptera frugiperda, was detected in 2020 in Queensland and is now established in various Australian states. FAW has so far caused no economic loss to cane but this incursion highlights the risk of future exotic Lepidopteran incursions such as sugarcane moth borers. Australia is also concerned about potential future incursions of Hemipteran vectors of pathogens. The focus of Australian research on exotic pest threats has included both on shore and offshore work (with collaborators in Asia and the Pacific) on preparedness including optimising diagnostic and detection techniques and incursion management approaches.

An overview of the SRA entomology research program and its highlights in relation to endemic and exotic pests and their sustainable management will be provided.

• From Augmentative Biological Control to Conservation Efforts in Colombia. Germán Vargas, Centro de Investigación de la Caña de Azúcar de Colombia, Cali, Colombia

Abstract: The sugarcane stem borers, Diatraea spp., are considered the most important pests in sugarcane in Colombia and management is achieved by releasing egg and larva parasitoids. In general, Diatraea saccharalis, is the species with the widest distribution in the Western Hemisphere and can be found infesting sugarcane from the U.S. to Argentina. In Colombia, the main species in sugarcane are D. saccharalis, distributed all over the country; D. indigenella, recorded in western regions, D. busckella, found all over the country; D. lineolata, recorded in the departments of Tolima, Magdalena, Valle and Choco; and D. tabernella, registered in western areas of Colombia and relatively recently in the Cauca River Valley (CRV).

In many sugarcane growing areas in the neotropics, the main component for pest management has been biological control since the introduction of Lixophaga diatraeae from Cuba to Louisiana in 1915, which, even though unsuccessful, was followed by several successful examples in other countries in the region. In Colombia, there have been efforts towards the biological control of Diatraea spp. since the early 1970s. Trichogramma spp. were the first parasitoids to be released, followed by releases of Cotesia flavipes that did not show adaptation to the conditions of the CRV and by the importation several tachinid flies. Some parasitoids showed interesting results whereas others never adapted to the Colombian conditions and particularly to the CRV, which is the most industrialized sugarcane growing area of the country. After the 1980s and up to this date, the study of losses under the CRV conditions, population dynamics, sampling procedures, and alternative methods of control has contributed to the development of a biological control program that has allowed to respond to unexpected population changes and to keep Diatraea spp. at population levels minimizing their economic impact. 

This presentation will provide an overview of sugarcane stem borer ecology under the conditions of the CRV in Colombia and discuss the experiences accumulated over four decades of implementing augmentation biological control as the main tool of IPM. This presentation will also discuss possible future actions to face climate change and changes in production practices while promoting conservation biological control. In this regard, the behaviour of the wild larval parasitoid of sugarcane borers in Colombia, Genea jaynesi, was observed under manipulation of broadleaf flowering weeds growing on field edges. It was found that conservation of broadleaf flowering plants was associated with higher abundance of G. jaynesi adults. In addition, field collections of Diatraea spp. larvae across the CRV between 2015 and 2019 revealed that 50% of all parasitized individuals of the four borer species (D. saccharalis, D. indigenella, D. busckella and D. tabernella) were attacked by G. jaynesi; indicating its importance and prevalence in the natural regulation of these pests. A series of concerted efforts have been implemented to demonstrate to sugarcane growers the advantages of maintaining plant shelters, hedge rows, and areas of preservation as source of food for natural enemies and conserving associated fauna to promote conservation biological control as an alternative to augmentation biological control for a more environmentally friendly sugarcane production system.

• A Novel Approach to the Sterile Insect Technique for Eldana saccharina Management in South Africa. Lawrence Malinga, South African Sugarcane Research Institute, Mount Edgecombe, South Africa

Abstract: In South Africa, the stalk borer Eldana saccharina (eldana) is an indigenous pest that significantly reduces sugarcane yield. Severe economic losses due to eldana in the South African sugarcane industry are estimated at approximately US$60 million annually. Researchers at the South African Sugarcane Research Institute (SASRI) have conducted research over many years to develop tools to enable sugarcane growers to sustainably manage this pest according to integrated pest management principles, with the sterile insect technique (SIT) being one of these tools.

SIT is a species-specific and environmentally benign method of insect control that depends on the release of sterile insects. The success of the SIT programme around the world can be ascribed to the fact that it has been based on an understanding of the developmental stages, behaviour, and population dynamics of the target species. Before embarking on area-wide integrated pest management programmes involving suppression of insect pests using SIT, consideration of the technical and economic feasibility of the approach is essential.

The SIT is commonly implemented by releasing partially sterile male insects into the wild. These partially sterile males then compete with wild males for mating with the wild females. After mating, the wild females that mated with the sterile male will produce some fertilized F1 eggs. F1 generation adults in the field are then sterile, and this is known as F1-inherited sterility. This will result in the eradication, reduction, containment, or prevention of the targeted pest population. Irradiation of the insects is done using gamma-ray or x-ray that irradiates the insects’ reproductive cells.

SASRI has been involved in the rearing of eldana since the 1970s, and for nearly two decades, the institute has been conducting SIT research on eldana control. Due to the unavailability of a nearby irradiation facility, SASRI is pioneering a novel approach to SIT. Instead of irradiating moths and releasing these directly, as in traditional SIT, the first-generation offspring are mass-reared and released. Significant progress has been made in understanding the factors and variables affecting the quality and the field performance of released moths. Valuable lessons learned from the preliminary SIT research have revealed that: (i) male moths irradiated at the dose of 200 Gy are as sexually competitive as wild males; (ii) the F1 population has a desirable male bias and greater ‘fitness’ than its irradiated parent; (iii) long-distance transportation for irradiation has no impact on pupal emergence; and (iv) weekly release of sterile F1 male moths in controlled cages reduces eldana populations and their damage to sugarcane. With a successful proof of concept, the SIT programme has the potential to be a viable control measure for eldana in sugarcane production.

• Bt Sugarcane in Brazil: Development, Efficacy Evaluation, Commercial Implementation, and Future Perspectives. Caroline Sakuno, Centro de Tecnologia Canavieira, Piracicaba, São Paulo, Brazil

Abstract: Sugarcane is cultivated on about 26 million ha in more than 100 countries worldwide and Brazil is the largest producer of sugarcane, with a projected contribution of 37% to the world’s production by 2028. The production of this crop has increased in recent decades and consequently, losses from attacks by the sugarcane borer, Diatraea saccharalis, the main pest of the crop, have also increased. In 2017, the Center of Sugarcane Technology (Centro de Tecnologia Canavieira [CTC], Piracicaba, São Paulo, Brazil) released commercially the first genetically modified (GM) sugarcane variety in Brazil. This variety, CTC20BT, produces the Cry1Ab protein for the control of D. saccharalis.

The commercial process to develop a GM crop has been broadly established through the last decades after the first GM crop approval in 1994. This process has continuously evolved to adapt to technological advances, such as genome editing tools. A commercial pipeline to develop a GM crop includes five phases: I) gene discovery: prospect and evaluate candidate genes for desirable traits, II) proof of concept: vector design, crop transformation and transgene tests for agronomic features and efficacy (greenhouse and field), III) early development: commercially transformation and selection of events with the desirable trait and equivalent of superior characteristics as the conventional crop variety, IV) advanced development: risk assessment studies and dossier preparation and V) pre-launch: regulatory submission, product development, and pre-marketing.

Since the first release, four sugarcane varieties have been approved commercially. To confirm the efficacy of this material, we conducted evaluations under field and greenhouse conditions using natural and artificial infestations with D. saccharalis, which showed evidence of control of the borer. In addition, bioassays with fresh leaf tissues and 25-fold dilution bioassays were performed in the laboratory throughout the crop cycle. Molecular mechanisms involved in cry resistant plants were accessed by global expression analysis (RNAseq) indicating differentially expressed pathways involved in the induction of proteins related to insect defence. Assessment of environmental effects of Bt sugarcane by analysis of soil microbial communities showed that the use of GM plants did not affect the structure and diversity of these communities, further emphasizing the biosafety of Bt sugarcane. These proof-of-concept studies allowed the assessment of efficiency in embryogenesis and plant regeneration, transformation efficiency, control efficiency and recovery of events, and performance relative to conventional sugarcanes indicating the reliability of Bt technology for this crop.

Lessons from the use of other Bt crops have provided clear evidence that implementing an effective insect resistance management (IRM) strategy is the key to delaying the evolution of resistance. Therefore, since the commercial launch, monitoring has been conducted using sentinel plots and F2 screen to detect resistant genotypes in field insect populations. In addition to the frequent monitoring of commercial technologies, efforts are currently focused on the launch of new varieties with new modes of action, resistance to other pest complexes, and tolerance to herbicides. Thus, the result of these technologies is a lower production cost compared to conventional sugarcane, meeting the industry’s demand for higher quality and yield.

The facilitators are:

Julien Beuzelin (University of Florida, USA), Cecilia Easdale (Ledesma, Argentina), and Nichanun Kernasa (Kasetsart University, Thailand).

Discussion

Q&A Session

Conclusion

Language

The Webinar will be conducted in English.

Further information

For further information, please contact Julien Beuzelin at jbeuzelin@ufl.edu or the ISSCT Secretariat at issct@intnet.mu

Please click here for short biodata on the presenters