Integrated management strategy of soil-borne fungi and nematodes in leafy vegetables grown in glasshouses

Main research question/goal

The most important fungal pathogens in the cultivation of butter lettuce under glass are Pythium spp., Sclerotinia spp., Rhizoctonia solani and Botrytis cinerea. They cause similar symptoms: the rotting of the lower leaves. In addition, problems with the nematodes Paratylenchus sp. and Pratylenchus penetrans occur regularly.  In addition, a wilting disease caused by Fusarium oxysporum f.sp. lactucae has been reported since 2015. This pathogen spreads rapidly throughout the entire production region in Flanders in greenhouses with butter lettuce. The objective of the FUNSLA project was to fill knowledge gaps about damage caused by nematodes and their population dynamics, the biology and epidemiology of soil-bound fungi, and the influence of environmental factors in this regard. This should lead to an integrated control strategy for smut pathogens and nematodes, in which growers would be assisted, e.g. through an app for lettuce diseases. In addition, the strengths, weaknesses, opportunities and threats of chemical and biological crop protection for lettuce cultivation were investigated in a SWOT analysis.

 

Research approach

The IPM strategy for the control of nematodes and soil-borne pathogens relies on several pillars, namely avoiding inoculum build-up, preventing infections and avoiding unnecessary spraying and soil fumigation. Damage thresholds were determined for the nematodes Paratylenchus sp. and Pratylenchus penetrans in pot trials. A list was made of leafy crops on which the nematodes multiply less successfully. In addition, the population structure of nematodes was monitored through regular soil analyses and the expression of fungal symptoms was monitored and related to environmental factors through analyses of lettuce with smut symptoms. For F. oxysporum f.sp. lactuae, several isolates were collected and identified for the first time in our country, necessary to gain insight in the distribution and building up of a further strategy. With the knowledge gained, recommendations were formulated that can reduce chemical treatments against soil-borne pathogens.

Relevance/Valorisation

The current market is forcing growers to make a strong commitment to cost price efficiency so that they have to specialise in a single crop. The year round cultivation of a monoculture butterhead lettuce, however, is accompanied by problems with soil-related diseases and nematodes. The constant presence of host plants ensures a rapid inoculum build-up of these diseases and pests in the greenhouse soil. The use of fungicides via foliar spraying and chemical soil disinfection against sclerotia of fungi and nematodes is increasingly restricted. The knowledge gained in FUNSLA supports growers in the decision to use chemical agents or alternatives. For the new lettuce disease, Fusarium, basic data have been collected for a follow-up project. The analysis of the lettuce cultivation system points in the direction of an approach that is no longer purely focused on economic profit. However, more sustainability is difficult to achieve in the current market system.

 

 

Funding provider(s)
VLAIO

External partner(s)
Inagro
PCG - Provinciaal Proefcentrum voor de Groenteteelt Oost-Vlaanderen vzw
PSKW - Proefstation voor de groententeelt Sint-Katelijn-Waver
UGent