Tracking movement of Meloidogyne spp and R. reniformis in a plasticulture system

Authors: SMITH, CODY - University Of Florida; FREEMAN, JOSH - University Of Florida; Burelle, Nancy

Submitted to: Proceedings of Methyl Bromide Alternatives Conference
Publication Type: Proceedings
Publication Acceptance Date: 9/10/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soil fumigation and treatments of nematicides have been the common protocol for pre-and in-season management of plant parasitic nematodes in vegetables. One issue not addressed is the depth at which the highest concentration of nematodes occur. In the US, application of nematicides is commonly done using 30 cm shanks. Current drip or shank applied fumigants do not move well across beds or downward in soil. Application at 30 cm provides a zone of protection for young transplants but may not be targeting the largest concentration of nematodes or providing season-long control. The purpose of this research was to track the seasonal movement of two plant parasitic nematodes (root-knot nematode and reniform nematode) in a 120 cm vertical soil profile through a 90 day watermelon cropping season. Experiments were conducted in the fall of 2016 and spring seasons of 2016 and 2017 at the North Florida Research and Education Center in Quincy, Florida. Seedlings of the hybrid rootstock ‘Carnivor’ were used in all experiments. In all seasons, three 120 cm long, 5 cm diameter core samples were taken from each rep using a Geoprobe system. Cores were collected on three different sampling intervals: pre-plant, mid-season, and season’s end. Nematodes were extracted from 100 cc of soil then counted. The results show that concentrations of both root-knot and reniform nematode were present in the 30-60 cm or 60-90 cm range at the pre-plant sampling date and were similar or higher compared to the 0-30 cm depth in all three experiments. The same held true for season’s end. Mid-season populations showed a more homogenous distribution. Both spring seasons saw an exponential growth in reniform populations between 0 and 90 DAP. Current alternative fumigants have lower diffusive properties than methyl bromide and do not provide the same level of soil coverage. This experiment demonstrates that an equivalent or greater number of root-knot nematodes reside at 30-60 or 60-90 cm depths compared to 0-30 cm at planting which would likely be out of reach for currently used fumigants and application techniques. This data further illustrates the need to target current fumigants with limited soil mobility to the areas where pest organisms reside.

Technical Abstract: Soil fumigation and in-row treatments of nematicides have been the common protocol for pre-and in-season management of plant parasitic nematodes (PPN’s) in vegetable production. One issue not addressed is the depth at which the highest concentration of nematodes occur. In the United States, application of nematicides is commonly done using 30 cm shanks. Current drip or shank applied fumigants do not move well laterally or downward and proper coverage is limited to the bed center. Application at 30 cm provides a zone of protection for young transplants but may not be targeting the largest concentration of nematodes or providing season-long control. The purpose of this research was to track the seasonal movement of two PPN’s (Meloidogyne spp. and Rotylenchulus reniformis) in a 120 cm vertical soil profile through a 90 day watermelon (Citrullus lanatus) cropping season. Experiments were conducted in the fall of 2016 and spring seasons of 2016 and 2017 at the North Florida Research and Education Center in Quincy, Florida. Experimental plots were arranged in a randomized complete block design with four replications. Black polyethylene mulch was used in both spring seasons and white-on-black mulch in the fall. Rows were spaced 2.44 meters apart, beds were 76.2 cm wide, 20.3 cm tall, and 18.3 m long. Seedlings of the hybrid rootstock ‘Carnivor’ (Cucurbita maxima x C. moschata) were spaced 91 cm within the row and were used in all experiments. In all seasons, three 120 cm long, 5 cm diameter core samples were taken from each rep using a Geoprobe system. Cores were collected on three different sampling intervals: pre-plant (0 DAP), mid-season (45 DAP), and season’s end (90 DAP). Soil cores were segmented into 30 cm sections (0-30 cm, 30-60 cm, 60-90 cm, 90-120 cm) then sub-sampled. Nematodes were extracted from 100 cc of soil then counted. Populations of Meloidogyne spp. and R. reniformis were identified by species and depth. The results show that concentrations of both Meloidogyne spp. and R. reniformis were present in the 30-60 cm or 60-90 cm range at the 0 DAP sampling date and were statistically similar and in some cases higher compared to the 0-30 cm depth in all three experiments. The same held true for season’s end (90 DAP). Mid-season (45 DAP) populations showed a mix of the aforementioned stratification or a more homogenous distribution. Both spring seasons saw an exponential growth in R. reniformis populations between 0 and 90 DAP sampling dates. Current alternative fumigants have lower diffusive properties than methyl bromide and do not provide the same level of soil coverage. This experiment demonstrates that an equivalent or greater number of Meloidogyne spp. reside at 30-60 or 60-90 cm depths compared to 0-30 cm at planting which would likely be out of reach for currently used fumigants and application techniques. This data further illustrates the need to target current fumigants with limited soil mobility to the areas where pest organisms reside.