Weed hosts of Globodera pallida from Idaho.
To determine the host status of common weeds found in potato fields of the Pacific Northwest, host suitability tests were conducted in a greenhouse. Reproduction of the potato cyst nematode (Globodera pallida; PCN) on hairy nightshade (Solanum physalifolium) and cutleaf nightshade (S. triflorum), black nightshade (S. nigrum) (Washington biotype), bittersweet nightshade (S. dulcamara) (Idaho biotype), redroot pigweed (Amaranthus retroflexus), kochia (Bassia scoparia) and common lambsquarters (Chenopodium album) were compared to reproduction on the potato cultivars Desiree, Russet Burbank (known hosts) and Sante (poor host). Plants were grown in 10 cm-diameter clay pots containing sandy loam soil previously fumigated with methyl bromide and inoculated with 10-150 cysts that were either collected from infested fields or raised in the secured greenhouse. Cysts were extracted from soil with a Fenwick can and the reproductive factor (RF) was determined. While both biotypes of hairy nightshade were suitable hosts of PCN, cutleaf biotypes, black and bittersweet nightshades were poor hosts. Russet Burbank and Desiree proved to be suitable hosts and Sante was a poor host of Idaho PCN. Although some cysts were recovered from pots containing the remaining weed species, they may have been part of the original inoculum. The significance of nightshade species (whether suitable or poor hosts) in eradicalion of PCN from infested fields cannot be overemphasized.