Submitted to: International Research Conference on Huanglongbing
Publication Type: Proceedings
Publication Acceptance Date: 2/7/2019
Publication Date: N/A
Interpretive Summary: Huanglongbing (HLB) is a devastating disease of citrus. Citrus production in Florida has dropped 70% in the last decade; HLB is also spreading through Texas and California. There is no known cure for HLB, necessitating that management strategies must be developed to maintain citrus productivity in citrus trees affected by HLB. Anaerobic soil disinfestation (ASD), is a treatment that alters the soil microbial community has demonstrated beneficial effects on vegetable crops. Our objective was to determine if ASD impacted HLB development in newly planted citrus trees. Although ASD did not impact incidence of HLB, trees growing in ASD-treated plots grew larger and produced more fruit than those in non-treated plots. ASD treatment has potential as a management strategy for HLB.
Technical Abstract: Numerous management strategies are currently being evaluated in an effort to maintain citrus productivity in trees affected by Huanglongbing (HLB). Anaerobic soil disinfestation (ASD) is a treatment that has been shown to improve productivity of vegetable crops. ASD involves amending the soil with a carbon source and an organic nitrogen source, covering the soil with gas-impermeable plastic mulch followed by irrigation to saturation. During treatment, the soil microbiome is shifted to facultative and obligate anaerobes. An experiment was designed to determine ASD effects on newly-planted citrus. The experiment compared soil -/+ ASD as the main treatment and rootstock as the subtreatment. Following ASD, Valencia orange scions grafted onto each of three rootstocks (Swingle citrumelo, Sour orange, or Kuharske citrange) were planted. Two trees on each rootstock were planted in four replicates per treatment. The experiment was conducted twice with one planting established in 2013 and the second in 2014 at the USDA research farm in St. Lucie Co., Florida, an area with intense ACP pressure and high incidence of HLB. Within two years after each planting, 100% of the trees in each planting were infected with CLas and expressed HLB symptoms. There were no differences in incidence of HLB between ASD treatments or rootstocks. However, both ASD and rootstock had significant effects on the soil microbial community. Rootstock had no impact on tree growth or productivity, but tree growth, as measured by stem and canopy diameter was greater in ASD treated plots vs non ASD-treated plots. In addition, there was ca. a 17% greater fruit yield in response to ASD treatment at the first harvest. ASD treatment is beneficial for citrus even when declining as a result of CLas infection.