Evaluation of summer and winter cover crops for variations in host suitability for Meloidogyne incognita, M. arenaria and M. javanica

Abstract

Summary Root-knot nematode (RKN) is an important pathogen on vegetables; therefore, planting a non- or poor host cover crop following a susceptible vegetable crop is a promising management option. This study builds upon previous studies and evaluates the variations in host status of cover crop candidates for reducing the reproduction of RKN populations (Meloidogyne incognita, M. arenaria and M. javanica) in Georgia, USA, to shed light on previous inconsistencies regarding the host status of cover crops and effectiveness in the field. Two glasshouse trials tested the host status of 14 plant species and 18 cultivars plus susceptible tomato ‘Rutgers’. Sixty days after inoculation, roots were evaluated for galling (GI) and egg mass index (EI). Gall formation was not a reliable indication of RKN reproduction for many cover crops, which had higher EI than GI. Based on GI, all cover crops were either non-hosts, ranging from non-hosts to poor hosts or poor hosts to all three RKN species, except blue lupine and hairy vetch, which were susceptible to all three RKN species and had a GI and EI equal to the susceptible tomato control. Based on EI, only bahiagrass, bermudagrass, marigold, millet and velvetbean were either non-hosts or ranged from non-hosts to poor hosts. Eleven cover crops varied in host status to the three RKN species screened, ranging from either non-host to poor hosts or poor hosts to susceptible, which could explain inconsistencies in glasshouse and field trials.

Nematicidal Potential of Sulla (Hedysarum coronarium L.) against the Root-Knot Nematode Meloidogyne incognita

“…Use as green manure seems to be the most suitable for the exploitation of the nematicidal potential of this plant, also in consideration of the agronomical benefits related to this practice. However, high attention should be given to seasonal period of green manures, so as to avoid spring–summer periods which are favourable to a potential RKN multiplication on sulla roots [ 60 ].…”

Successional effects of cover cropping and deep tillage on suppression of plant‐parasitic nematodes and soilborne fungal pathogens

“…25 Tropical sunn hemp (Crotalaria juncea) may be an excellent candidate for vegetable rotations, as it fixes nitrogen, 26 produces a large volume of biomass, 27,28 suppresses PPN through production of allelopathic pyrrolizidine alkaloids, 29 and is a poor-host to RKNs. 26,30 There are in vitro experiments showing the potential of pyrrolizidines alkaloids suppressing fungal organisms; however, field studies on its effect on fungal pathogens are limited. 31 Cereal rye is commonly planted in the fall as a forage crop for livestock in Georgia 32 and has been suggested as a cover crop for nematode and weed control due to the production of allelopathic benzoxazinoids 33 and rapid growth, producing large volumes of biomass during the winter season.…”

“…40 Rye may also indirectly suppress soilborne pathogens by enhancing organic matter and soil microbial community. 30 The effectiveness of soilborne pathogen suppression by cover crops can vary greatly depending on sufficient biomass production. The lack of M. incognita suppression has been attributed to low cereal rye biomass production.…”

“…For example, winter rye in a 2‐year rotation of soybean, sweet corn, potato, and canola reduced disease severity of black scurf caused by Rhizoctonia solani and common scab of potato caused by Streptomyces scabies 40 . Rye may also indirectly suppress soilborne pathogens by enhancing organic matter and soil microbial community 30 …”

“…Tropical sunn hemp ( Crotalaria juncea ) may be an excellent candidate for vegetable rotations, as it fixes nitrogen, 26 produces a large volume of biomass, 27,28 suppresses PPN through production of allelopathic pyrrolizidine alkaloids, 29 and is a poor‐host to RKNs 26,30 . There are in vitro experiments showing the potential of pyrrolizidines alkaloids suppressing fungal organisms; however, field studies on its effect on fungal pathogens are limited 31 .…”