Files
Abstract
Plant-parasitic nematodes (PPN) limit vegetable yield. Our aim was to assess the threat of PPNs on vegetables and investigate potential management tactics. In 2018, a surveillance study was conducted on 246 vegetable fields from 29 counties. Root-knot nematode (RKN) was the dominate PPN infesting two thirds of sampled fields. Patterns of PPN community suggest cropping systems have a greater effect on PPN population dynamics than the edaphic factors measured in this study. Five RKN species (M. incognita, M. arenaria, M. javanica, M. floridensis and M. haplanaria) from RKN-infested fields were identified by species-specific PCR and mitochondrial haplotyping. Meloidogyne floridensis and M. haplanaria were detected in Georgia and pose a threat by reproducing on Mi-resistant vegetable cultivars. Most fields were infested with M. incognita (91.9%) or M. arenaria (36.0%), with many fields mixed with both species (29%). Monthly deep-soil sampling found seasonal fluctuations in the vertical distribution of RKN and Nanidorus spp. PPN abundance increased from mid-spring to late winter as PPNs completed multiple life-cycles and then stopped reproduction in the winter fallow period. Patterns of seasonal vertical distribution suggest an illuvial zone barrier in the north region has a prominent role. Since a majority of RKN dwell at ≤ 30 cm during the summer, fumigants/nematicide application are suggested for this season to minimize risk of escapees. Cover crop-fallowing is an important cultural practice for PPN management. Cover crop greenhouse host-status trials found many cover crops with low root galling, yet females successfully produced egg masses. Based on egg mass index, bahiagrass, bermudagrass, marigold, millet, and velvetbean were either nonhosts or ranged from nonhosts to poor hosts. A field trial testing cover crop-fallow seasons and deep tillage on nematode suppression found sunn hemp suppresses M. incognita independent of tillage practice, whereas deep tillage suppresses Rhizoctonia solani, Sclerotinia sclerotiorum, and Nanidorus minor. Winter rye did not suppress RKN. Fall sunn hemp had higher biomass than spring sunn hemp and reduced root galling even in the second subsequent vegetable. These findings provide new insights for vegetable growers to develop programs of sustainable PPN management.