Innovative Approaches for Detection and Management of Fruit Rot Diseases in Annual Hill Plasticulture Strawberry Production System

Abstract

Fruit rot diseases, including anthracnose fruit rot (AFR) and Botrytis fruit rot (BFR) (grey mold) in strawberries, are caused by the acutatum species complex and Botrytis cinerea, respectively. These diseases present a major challenge to sustainable strawberry production in the United States, impacting both perennial and annual systems globally. The pathogens can survive in the transplants and the soil rhizosphere and later infect the plants. As a first step for disease management, it is crucial to identify plant diseases like AFR in their early stages. In recent years, remote sensing, including multispectral imaging, offers an advanced technological method for the early identification, mapping, and spatial tracking of pest and disease outbreaks. Additionally, anaerobic soil disinfestation (ASD) offers a promising alternative to conventional chemical fumigation techniques. It has proven effective in suppressing various pests, including fungi, bacteria, weeds and nematodes, while also enhancing soil health and crop production. Beneficial bacteria, like Bacillus spp., play a crucial role as biocontrol agents by inhibiting the growth of plant pathogens and promoting plant growth. The first study aimed to develop a new approach that integrates small unmanned aerial vehicles equipped with multispectral imaging (MSI) camera sensors to accurately identify the best vegetation indices (VIs) for the early detection of AFR caused by Colletotrichum nymphaeae and Colletotrichum fioriniae in strawberries. The results indicated that the Chlorophyll Index (CI) and Green Normalized Difference Vegetation Index (GNDVI) had the strongest correlations with AFR disease severity (%) and showed the most significant differences among all the VIs and reflectance values when distinguishing between infected and healthy plants across the two growing seasons. They consistently correlated with AFR disease severity during the early stages of fruit development. Furthermore, the notably lower reflection of CI values in C. nymphaeae-infected plants, compared to those infected with C. fioriniae and healthy plants, highlights the potential for differentiating between the two subspecies within the C. acutatum species complex. This approach could be a promising tool to monitor the severity of AFR disease infestations using field maps and drones to apply appropriate management techniques. The second study aimed to assess how ASD, beneficial bacteria, and their combinations could help reduce fruit rot diseases in strawberries, manage weeds, and improve crop yield and postharvest fruit quality. The results showed that ASD treatment significantly lowered the biomass of diseased fruits including AFR and BFR compared to the non-fumigated and Pic-Clor 60 fumigation treatments. Post-plant treatments that included B. velezensis IALR619, TerraGrow, and Oxidate 5.0 + TerraGrow led to a reduction in AFR compared to the non-inoculated treatment in the first growing season. The ASD and Pic-Clor 60 treatments resulted in a lower weed density in the strawberry planting holes compared to the non-fumigated control. The ASD treatment improved fruit firmness, total soluble solids (TSS), and the pH of fruit juice when compared to Pic-Clor 60 fumigation but reduced marketable and total yield. Our findings show that ASD and beneficial microbes have potential use for managing fruit rot diseases in organic farms, small farms, and limited resource growers.