Date of Award
8-2024
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Plant and Environmental Science
Committee Chair/Advisor
Dr. Churamani Khanal
Committee Member
Dr. Guido Schnabel
Committee Member
Dr. Joseph Anthony Roberts
Abstract
Nematodes are a growing threat to the multi-billion-dollar strawberry industry in the US due to the lack of safe and effective management methods. Limited information on the distribution of nematodes in fumigated plasticulture strawberry fields further complicates their management. Additionally, climatic anomalies like rising soil temperatures and heat waves are occurring more often, and their impact on crop growth and nematode reproduction is not well understood. The current study was conducted with two main objectives: i) understand distribution and population densities of nematodes associated with plasticulture strawberry production in South Carolina, and ii) understand the impact of short-term high heat exposure on reproduction biology of nematodes. During the 2023 production season, 14 strawberry plasticulture farms from three different production regions in South Carolina (Upstate, Midlands and Pee Dee) were included in the survey, where 76 soil and 64 leaf samples were collected. The most frequent nematode in the entire state was Tylenchus spp. (66%), followed by stubby root (Trichodorus spp.) (39%) and spiral (Helicotylenchus spp.) (9%) nematodes. Dagger (Xiphinema spp.), root-knot (Meloidogyne spp.), sting (Belonolaimus longicaudatus), foliar (Aphelenchoides spp.), ring (Mesocriconema spp.) and stunt (Tylenchorhynchus spp.) nematodes were also found at lower frequencies (2-5%). Sting nematodes were found in Pee Dee region with population density of 273 nematodes/100cm³ of soil, which is several hundred folds higher than the current damage threshold. The presence of sting nematodes in Pee Dee region was not surprising because strawberry fields in this region contain 84-94% sand, which is ideal for sting nematodes. For assessing the impact of short-term heat exposure on nematode reproduction biology, Meloidogyne enterolobii and tomato were employed as model nematode and host, respectively. Nematode second-stage juveniles (J2) were exposed to either 42 °C or 44 °C for 60 minutes and subsequently inoculated to tomato seedlings in a growth room. After 8 weeks of inoculation, reproduction of nematodes exposed to 44 °C was significantly reduced by 78% for egg production and 77% for J2 production relative to that of control group that were not exposed to heat before inoculation. Similarly, the reproduction of nematode exposed to 42 °C was reduced by 33% for egg production and 46% for J2 production compared to that of control. Interestingly, the plant root biomass was reduced by 26% when nematodes treated at 44 °C for 60 minutes, were inoculated. This suggests virulence of nematode may be increased upon exposure to certain higher temperatures for a short duration. Furthermore, hatchability of the next generation of the nematode was reduced by 28-45% relative to the control. The current study, listing nematode population densities and their distribution across strawberry plasticulture fields in SC, serves to raise awareness about the presence of nematodes within plasticulture strawberry production and their probable yield impact in the future. Nematode reproduction and virulence may be impacted by higher soil temperatures. Further studies mimicking natural soil environmental conditions are needed to better understand nematode biology and its impact on crop yield.
Recommended Citation
Alarcon Mendoza, Ivan A., "Survey of Nematodes Associated With Strawberry in South Carolina and Evaluation of Short-Term Heat Exposure on Nematode Reproduction Biology" (2024). All Theses. 4368.
https://open.clemson.edu/all_theses/4368