Crop losses attributed to pests and pathogens are estimated tobe approximately 30% on a worldwide basis averaged across all crops. As the acreage on which biofuel crops are grown expands, we can expect pests and pathogens will also have a significant impact on both biomass yield and biomass quality. Little is known of the pests and pathogens that may cause diseases on new biofuel crops, like Miscanthus and switchgrass. With this project, we are surveying the pests and pathogens that occur on Miscanthus. Such information will serve the needs of breeders, as genetic resistance to pests and pathogens is likely to be an important form of disease control for biofuel crops. Knowledge of the most important pathogens will help agronomists and plant pathologists develop integrated pest and pathogen management strategies to minimize losses.

On a broader scale, a comprehensive catalogue will provide those interested in the inter-migration of pests and pathogens between biofuel crops and neighboring food crops or native plant species with a basis for choosing dominant organisms to study. In addition, these data should stimulate the development of robust, simple to use, cost-effective diagnostic devices to support the development of integrated pest management strategies, which rely on accurate field-level assessments of pest density. In addition to these immediate benefits of these surveys, knowledge of the major diseases and insect pests also will contribute to research on biomass quality. Typical plant responses to pathogen and insect attack include the production of anti-microbial secondary metabolites and the reinforcement of the cell wall. Modifications in the cell wall may hinder decomposition; while some of the secondary metabolites may poison fermentation. Finally plant pathogens may serve as a source of highly adapted cell wall degrading enzymes; since the plant cell well and cuticle are the first barriers many pathogens must overcome in order to be successful. Ongoing interactions with those working on the decomposition and fermentation steps of the lingo-cellulose process should aid in the optimization of such processes in light of projected disease impacts on biomass quality.

The primary objectives of our program are: 1) To survey the insect fauna, plant diseases, and nematodes in large Miscanthus and switchgrass (Panicum virgatum) plots throughout Illinois and other appropriate domestic and foreign sites and assess the potential for biomass reduction by candidate insect pest and plant pathogen species most likely to represent an economic threat; 2) To establish greenhouse and small-plot experiments with Miscanthus and switchgrass with precise levels of candidate insect pest densities to determine potential effects on biomass production; 3) To establish greenhouse experiments with common, potentially damaging nematode species, to determine their pathogenicity to Miscanthus and switchgrass; 4) To determine the effect of common soilborne pathogens with wide host ranges (i.e. Rhizoctonia, Fusarium, and Pythium) on Miscanthus growth in greenhouse trials and in field trials; and 5) use DNA-based methods to identify microbes.

Very little has been described concerning the potential for insect pests to injure Miscanthus. A review of insect pests of sugarcane (Saccharum officinarum L.), a close relative of Miscanthus, provides preliminary insight. It has been estimated that more than 1,500 insect species worldwide feed on sugarcane. Foliage feeders—Two species of armyworms, fall armyworm (Spodoptera frugiperda) and true armyworm (Pseudaletia unipuncta), feed on sugarcane foliage and are common pests of corn throughout the eastern half of the United States. Sap feeders—Aphids feed on plant sap and are significant vectors of viruses. Corn leaf aphids (Rhopalosiphum maidis) colonize corn, barley, sorghum, millet, broomcorn, sugarcane, sudan grass, and other wild and cultivated grasses and vector maize dwarf mosaic virus, barley yellow dwarf virus (BYDV), and mosaic virus of sugarcane. It has been determined that Miscanthus sinensis is a suitable host for R. maidis and could potentially vector BYDV, a potential limitation to cultivation of Miscanthus in the United Kingdom. Other aphid species that infest crops grown in the United States and vector disease pathogens include greenbugs (Schizaphis graminum), yellow sugarcane aphids (Sipha flava), English grain aphids (Sitobion avenae), and bird cherry-oat aphids (Rhopalosiphum padi). Although aphid species might not cause direct losses in biomass production of Miscanthus, their role as potential vectors of disease pathogens of Miscanthus should be elucidated. Miscanthus also could be a reservoir of viruses that infect other crops such as sorghum, small grains, and corn. Soil insects—Reductions in stands of Miscanthus caused by a complex of soil insect pests, including white grubs (Scarabaeidae) and wireworms (Elateridae), could significantly reduce biomass production. Wireworms and white grubs are an economic threat to many field crops, including corn, each year, and both have been implicated as stand reducers of sugarcane. Wireworms are long-lived insects with some species living as long as 5 years as larvae. An infestation of wireworms in Miscanthus could cause economic losses for several years. Corn rootworms (Diabrotica species) are the most important insect pests of corn in North America. Because rootworms can survive on several species of grasses, their survival on Miscanthus could have significant economic consequences. Stalk borers—Approximately 50 species of lepidopteran borers are considered pests of sugarcane, including the sugarcane borer (Diatraea saccharalis). A close relative, the southwestern corn borer (Diatraea grandiosella), is widely distributed in the United States, from Arizona to Alabama and north to Kansas, southern Missouri, and southern Illinois. Although more distantly related, the European corn borer (Ostrinia nubilalis) has a very large host range (more than 200 species of plants) and could be a potential threat to Miscanthus. In addition, Miscanthus might serve as a breeding site for European corn borer moths that disperse to corn to lay eggs.

One of the most important components of the soil biota affecting biomass production is the nematode community. Soil- and plant-dwelling nematodes affect plants directly and indirectly. Root-feeding plant-parasitic nematodes reduce biomass production in monocultures and are often involved in the etiology of diseases caused by soil-borne fungi. Plant-parasitic nematodes that attack perennial grass species are ubiquitous in Illinois due to its prairie natural history, and include such economically important genera as Criconemella (ring nematode), Heterodera (cyst), Hoplolaimus (lance), Meloidogyne (root-knot), Paratrichodorus (stubby root), Pratylenchus (lesion), and Xiphinema (dagger). Of these genera, the root–knot nematodes are considered to be the most economically important plant-parasitic nematodes in the world. The northern root-knot nematode (M. hapla), which is widespread in Illinois, has been shown to be well adapted to ornamental Miscanthus species. Root-knot nematodes are considered to be the most economically important plant-parasitic nematodes in the world. Second only to the root-knot nematodes are the cyst nematodes, several species of which attack a wide range of monocots, including Saccharum officinarum.An equally important component of our program concentrates on the molecular characterization of pathogens. As a complement to the visual methods of pathogen identification, plant samples from both healthy and diseased plants are being harvested for the purpose of using DNA-based methods to identify microbes. The rationale for taking this approach is that some pathogens may be latent – present at levels insufficient to cause disease under the field conditions present. Such microbes can serve as a reservoir to seed future disease outbreaks under different environmental conditions. Furthermore, some microbes can be difficult to identify based on morphological and growth characteristics alone and DNA-based identification may help resolve these ambiguities. Finally, the DNA-based methods allow the detection of beneficial microbes, such as endophytic fungi. As knowledge develops regarding the spectrum of dominant pathogens for Miscanthus and switchgrass, permits will be sought to bring isolates to the University of California, Berkeley for additional growth chamber trials.