Plant Pathogens and Control Strategies in Aquaponics

Abstract

Among the diversity of plant diseases occurring in aquaponics, soil-borne pathogens, such as Fusarium spp., Phytophthora spp. and Pythium spp., are the most problematic due to their preference for humid/aquatic environment conditions. Phytophthora spp. and Pythium spp. which belong to the Oomycetes pseudo-fungi require special attention because of their mobile form of dispersion, the so-called zoospores that can move freely and actively in liquid water. In coupled aquaponics, curative methods are still limited because of the possible toxicity of pesticides and chemical agents for fish and beneficial bacteria (e.g. nitrifying bacteria of the biofilter). Furthermore, the development of biocontrol agents for aquaponic use is still at its beginning. Consequently, ways to control the initial infection and the progression of a disease are mainly based on preventive actions and water physical treatments. However, suppressive action (suppression) could happen in aquaponic environment considering recent papers and the suppressive activity already highlighted in hydroponics. In addition, aquaponic water contains organic matter that could promote establishment and growth of heterotrophic bacteria in the system or even improve plant growth and viability directly. With regards to organic hydroponics (i.e. use of organic fertilisation and organic plant media), these bacteria could act as antagonist agents or as plant defence elicitors to protect plants from diseases. In the future, research on the disease suppressive ability of the aquaponic biotope must be increased, as well as isolation, characterisation and formulation of microbial plant pathogen antagonists. Finally, a good knowledge in the rapid identification of pathogens, combined with control methods and diseases monitoring, as recommended in integrated plant pest management, is the key to an efficient control of plant diseases in aquaponics.

Biocontrol of Phytopathogens under Aquaponics Systems

“…Aquaponics has been compared with aquaculture [2,7,8] and hydroponic [9][10][11][12] technologies in terms of production and profitability. Up to now, the research on aquaponics has been focused on sustainability [13][14][15], economic optimization [16][17][18], functional setup [19,20], stocking density [21,22], cultivation media [23,24], water recirculation [25,26], food safety [9,27], fish-plant pathogens [6,28] and beneficial microorganisms [29,30].…”

“…Recently, it has been demonstrated that a complete understanding of the hydroponic subsystem is essential to improving the whole aquaponics system [31]. One of the main difficulties related to aquaponics system is the potential dissemination of pathogens [6], because water recirculation and controlled parameters such as temperature provides the perfect environment for pathogen proliferation [28]. Evidence of previous outbreaks in aquaculture and hydroponics shows the consequences of such events.…”

“…Diseases control is mainly based on disinfecting water methods at various points of the aquaponics systems, depending on the method [6]. Chemical and non-chemical disinfection methods have been applied in aquaponics and hydroponics systems to kill pathogens on the recirculating water [6,28]. However, these methods need to be administrated carefully because they could be harmful to humans, fish, plants and beneficial microorganisms [35].…”

“…However, these methods need to be administrated carefully because they could be harmful to humans, fish, plants and beneficial microorganisms [35]. At the moment, there is no pesticide nor bio-pesticide specifically developed for aquaponics systems [6,28,35,36]. Somerville et al [36] mentioned inorganic compounds which could be used against fungi in aquaponics.…”

Water Quality in the Cultivation of Catfish (Clarias gariepinus) and Nile Tilapia (Oreochromis niloticus) in the Aquaponic Biofloc System

“…controlling water quality and aquaculture of aquaculture, based on these three mutually sustainable matters, a polyculture cultivation system was created to increase aquaculture production. Basically catfish have a pattern of life at the bottom of a pond or at the edge of a pond, while tilapia has a life pattern in the middle layer to the bottom of a water pool [2,3], so that with different aquatic habitats it is possible to cultivate together or ordinarily called a communal system. According to [4], fish commodities that support aquaponics cultivation are catfish, because catfish produce more fish feces than other fish.…”