Project : USDA ARS

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Research Project: Management and Biology of Arthropod Pests and Arthropod-borne Plant Pathogens

Location: Emerging Pests and Pathogens Research

2023 Annual Report

Accomplishments
1. Isolated and identified entomopathogenic fungi from the highly destructive and globally invasive insect, the fall army worm (Spodoptera frugiperda). Fall army worms are highly destructive invasives, yet little is known about their microbial symbionts that could be harnessed or targeted for biological control. In collaboration with University researchers, ARS scientists at Ithaca, New York, characterized the fungal microbiome of S. frugiperda. Fungi cultured from this insect were accessioned into the ARS entomopathogenic fungi collection. Identification of new fungi provides options for biological control and management of fall army worms.

2. Identified several isolates producing filtrates highly bioactive against potato cyst nematode. Cyst nematodes are persistent and damaging pests of many agricultural crops. Methods of control remain limited, with genetic sources of resistance losing efficacy, and crop rotations being economically nonviable. We obtained funding from ARS (ARS State Partnership Potato Program) to screen fungi previously isolated from the soybean cyst nematode against the potato cyst nematode and were awarded a new contract with stakeholder groups in New York, (NY Corn and Soybean Growers) for FY 2023 to identify new fungi native to NY from soybean cyst nematode. The research on potato cyst nematode identified two fungi producing filtrates with high toxicity to the potato cyst nematode that can be explored as soil drench or seed coat applications to control this pest.

3. Herbicidal control of black swallow-wort. Black swallow-wort (Vincetoxicum nigrum) is a European twining vine that was introduced into eastern North America. Herbicides can be an effective management tool for invasive plants but had not been studied for black swallow-wort. Scientists from ARS in Ithaca, New York, and Cornell University evaluated glyphosate (two products) and triclopyr, with or without mowing. Both glyphosate products greatly reduced black swallow-wort biomass as well as cover and stem densities, but mowing several weeks before spraying did not always increase the effectiveness of herbicide treatments. Triclopyr was ineffective. Repeated, single applications of glyphosate can be useful for the management of black swallow-wort.

4. Knapweed population model helps guide control efforts. The European perennial plants spotted knapweed (Centaurea stoebe subsp. micranthos) and the hybrid meadow knapweed (C. x moncktonii) are invasive in grasslands and pastures across North America, including in the Northeast. The two species may develop similarly and therefore be controlled by targeting the same life stages. Scientists from ARS in Ithaca, New York, and the University of Vermont developed northeastern plant population models of the two species that identified key points of the plants’ life cycles to be targeted. Both species have similar life histories and therefore both species will likely be controlled through increased mortality of older seedlings and juvenile plants as well as delaying the maturation of vegetative individuals. Using this information, specific chemical, mechanical and biological control tactics can be developed for these invasive knapweeds.

5. Development of innovative delivery methods for insect-killing fungi. Consistent delivery of spores in laboratory and field conditions is a persistent challenge for successful evaluation and application of insect-killing fungi. ARS sientists at Ithaca, New York, developed a laboratory bioassay to briefly expose and maintain ambrosia beetles on artificial medium for screening virulence of potential biocontrol fungi. These methods provide a pathway for collaboration with university and ARS partners to rapidly screen entomopathogenic fungi against emerging invasive insect pests.

6. Discovery of a new virus infecting upland cotton. The United States is the world’s third largest producer and the leader in cotton exports. Cotton leafroll dwarf virus (CLRDV) is an emerging RNA viral pathogen of cotton transmitted in the field by the cotton aphid. Viral symptoms in the field have been challenging to understand and pinpoint to CLRDV alone. ARS scientists in Ithaca, New York, hypothesized that other plant viruses may be co-infecting cotton with CLRDV. Using different molecular and computational tools, ARS scientists in partnership with university colleagues discovered a new DNA virus infecting cotton growing in Mississippi and tentatively named the virus cotton virus A (CotV-A). Similar to other DNA plant viruses, they discovered that copies of the CotV-A genome are inserted into the genome of upland cotton, which may give rise to virus infection. Importantly, the team developed a method to distinguish between the real CotV-A infection and copies of CotV-A in the cotton genome by specifically degrading the virus copies in the cotton genome prior to a diagnostic test. The cotton industry was informed about the new virus and a paper has been published. A new grant was funded by the Department of Homeland Security to determine how widespread CotV-A is in upland cotton production in the United States. Additional research is needed to determine whether CotV-A can cause detrimental effects in cotton production, if the virus copies inserted in the upland cotton genome can initiate a real virus infection or whether the virus is transmitted by insects.

7. Plant-based peptides block insect transmission of the citrus greening disease bacterium. Citrus growers need effective strategies for managing citrus greening disease, also known as Huanglongbing (HLB). The presence and, therefore, the likely spread, of HLB within California are a major concern for growers because of the mobility of the Asian citrus psyllid (ACP), the insect vector of citrus greening in the United States. In Florida, the disease is endemic and growers need treatments to mitigate infection in existing groves and prevent transmission into new plantings. Organic growers, in particular, seek HLB management strategies that do not rely on synthetic chemicals. USDA ARS scientists discovered plant-based peptides that have the ability to thwart the spread of the HLB bacterium by the ACP. The work represents a collaboration among a team of USDA, University and industry partners and was funded by a CRADA with a small agri-businesss in Florida and a grant from the California Citrus Research Board, a consortium of growers in California. A patent has been filed and a preprint describing the peptides is available. These plant-based peptides have different killing modes of action that could effectively control citrus greening and/or prevent ACP from transmitting the pathogen to citrus trees.

8. Plants to the rescue from the next global pandemic. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a pathogenic virus that causes severe respiratory syndrome in humans. SARS-CoV-2 is related to SARS-CoV-1 and Middle Eastern Respiratory Syndrome (MERS)-CoV, which emerged in humans in 2003 and 2012, respectively. SARS-CoV-2 is responsible for the 2019 pandemic and COVID-19 disease. COVID-19 disease results in a range of outcomes, ranging from asymptomatic infection to patient death. To date, global vaccinations for SARS-CoV-2 protections are underway, but additional treatments are needed to prevent infection among naïve and even vaccinated individuals. ARS scientists from Ithaca, New York, and Fort Pierce, Florida, together with a CRADA partner, demonstrated plant production of small, functional molecules, referred to as nanobodies, interfere with the molecular interactions required for virus spread in humans. Production of plant-based nanobody therapies to control virus spread represents a promising new development in the mitigation of the COVID-19 pandemic.

U.S. DEPARTMENT OF AGRICULTURE

Emerging Pests and Pathogens Research: Ithaca, NY