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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Mycology and Nematology Genetic Diversity and Biology Laboratory » Research » Publications at this Location » Publication #354732
Title: Nematodes associated with invasive spotted knapweed

Author
item GARCÍA DE LA CRUZ, RUBÉN - Colegio De Postgraduados
item KNUDSEN, GUY - University Of Idaho
item DANDURAND, LOUISE-MARIE - University Of Idaho
item Carta, Lynn
item NEWCOMBE, GEORGE - University Of Idaho

Submitted to: Nematropica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2019
Publication Date: 1/26/2020
Citation: García De La Cruz, R., Knudsen, G.R., Dandurand, L.C., Carta, L.K., Newcombe, G. 2020. Nematodes associated with invasive spotted knapweed. Nematropica. 49(2):200-207.

Interpretive Summary: Invasive weeds cost billions of dollars in damage to U.S. farmers, range managers and homeowners every year. The annual economic cost of invasive spotted knapweed in North America is $150 million. One approach to designing new, safe means of controlling this weed problem that originated in Eurasia is to understand the interactions of North American soil organisms that may impact potential biocontrol of this invasive weed. In this report, an ARS scientist from Beltsville, Maryland in collaboration with scientists from the University of Idaho in Moscow and the Postgraduate College, Tabasco, Mexico, determined which nematodes (a type of roundworm) were present in three Idaho fields with spotted knapweed at three times during the summer. They discovered that the nematodes were not present in the plant tissue or close to the roots, but only in the bulk soil away from the roots. No damaging plant-parasitic nematodes were found. The results are significant because they indicate that nematodes in these fields have not adapted to the presence of spotted knapweed and are not likely to damage the weeds or decrease the effectiveness of biocontrol fungi that might be applied to control the weeds. This research will be used by agronomists and weed scientists to optimize strategies to control spotted knapweed in the field.

Technical Abstract: Release from plant-feeding nematodes of native ranges might contribute to plant invasions. However, nematode damage surveys and diversity inventories are largely limited to crop plants. To our knowledge no invasive plant has ever been compared in its native and invaded ranges for damage due to plant-feeding nematodes. The aim of this study was to take the first step towards testing this nematode release hypothesis by isolating and determining nematode taxa and trophic groups associated with spotted knapweed (Centaurea stoebe) in its invaded range in western North America. Three sites invaded by spotted knapweed were selected near Moscow, Idaho, USA. Soil samples, roots, and shoot systems of C. stoebe were collected in summer, 2012 at the following times: in June (young-rosette), July (flowering), and August (bolting). Plant parts used for nematode sampling were roots and leaves. Sixteen nematode taxa were identified from soil samples. Bacterial feeders and omnivorous predators were the most dominant groups, whereas plant feeders were found to have the lowest population levels. Aphelenchoides, Aphelenchus, Ditylenchus and Tylenchus were characterized as fungal feeders, and Aphelenchus (400 individuals per 100 g of soil) was the most prevalent fungivorous genus found in the bulk soil, followed by Aphelenchoides (120 nematodes per 100 g of soil). Even though almost all nematode trophic groups coexisted with spotted knapweed in both the rhizosphere and in the bulk soil, no nematodes were obtained from roots and leaves. Centaurea stoebe could be in a state of nematode release in western North America relative to its native range in Eurasia. The next step in the native range is to see if the plant-feeding nematodes known to occur there with C. stoebe actually damage or in some way limit the plant.