VALIDATION OF “PROCULTURE” MODEL TO PREDICT SEPTORIA TRITICI DEVELOPMENT ON
WINTER WHEAT IN THE GRAND-DUCHÉ OF LUXEMBOURG IN 2001.
M.El Jarroudi1 , B.Tychon1 , H.Maraite2
1
Fondation Universitaire Luxembourgeoise , Avenue de Longwy B-6700, Arlon, Belgium
2
Unité de Phytopathologie, Université Catholique de Louvain (UCL), Place Croix du Sud 2, B-1348 Louvain-la-Neuve, Belgium.
Introduction
One of the most serious foliar diseases on winter wheat in the G-D of Luxembourg which farmers need to take into account when deciding upon fungicide application during stem elongation is septoria leaf blight caused by Septoria tritici Roberge in Desmaz (anamorph of Mycosphaerella graminicola) (El Jarroudi et al., 2001).
The disease can result in severe crop damage during summer, leading to substantial yield losses ores (Hunter et al., 1999). Management of S. tritici aims at keeping the top three leaves of the cereal free from infection, as these leaves make the main contribution to grain yield (Shaw & Royle, 1989).
The objective of this work is to validate in G-D of Luxembourg the decision-support for S. tritici control “Proculture” developed for Belgium at the Unit of Phytopathology, UCL
(Moreau& Maraite,1999and 2000).Phenoloy in winter wheat and S. tritici development were monitored on the upper leaves in 2001 in trials set up at Everlange and Reuland, in the
G-D of Luxembourg.
Material and Methods
The « Proculture » model simultaneously assesses the development of each of the last five leaf layers of the crop and the availability of inoculum on or close to those leaves based on weather conditions favoring infection by M. graminicola. The software runs with hourly meteorological data of relative humidity (RH), air temperature and rainfall (fig. 1). In addition to weather data, crop sowing dates and crop phenological stages are necessary to run the model. The combination of the disease module with the phenological module allows the simulation of the diseases
development in the canopy (Moreau&Maraite,2000). The simulation model can be used to predict primary and secondary infection expressed or in incubation if correct information on leaf emergence is provided. The criteria used to determine favorable conditions to infection by the pathogen, the latent period and inoculum dispersion in the canopy, have been described in detail (ElJarroudi et al., 2001).
The progression of the disease is evaluated in a dynamic way. Such monitoring is impossible through regular observations. Therefore, information on the infection status is simulated before symptoms appear, quite on time for en efficient control of the disease by fungicide supplies.
Results
In Everlange during year 2001, the emergence of leaf F3 (flag leaf is F1) began around the 21 April. This day, the symptoms were already observed on F5. The first symptoms on F4 were observed the 7th of May and on F3, the 14th of May. Thus F3 was infected most probably by the inoculum produced on F5 at the end of April. Leaf F2 was infected at the beginning of its
emergence by F4 during the first 10 days of May. Some F1 were infected during their emergence by F3 towards around the14th of May.
In Reuland, in 2001, leaves F5 and F4 were infected during their emergence. Inoculum had already been produced on F5 when F3 was emerging (26 April) leading to early infection of this leaf level the 27th of April. F2 was infected most probably by F3 and to a lesser extend by F4.
The first symptoms on F1 were detected the 25th of June. The flag leaf was infected by F2.
Good agreement was observed in 2001 between model data output and field observations of the disease (table 1).
Figure 1 :
Output of the Septoria risk simulation model for year 2001 in winter wheat fields at Everlange and Reuland.
A : daily values of air mean temperature (°C) and rainfall (mm) measured at Everlange and Reuland.
B : number of hours per day of high probability of infection at Everlange and Reuland.
C : lines : leaf area development (0-100 %) of leaves F5 to F1.
a Everlange b Reuland
Table 1 : Period / leaves F5 F4 F3 F2 F1 Total F5 F4 F3 F2 F1 Total
Agreement (%) between Forecasted and expressed 16 10 7 6 6 45 16 11 8 7 5 47
forecasted and observed Forecasted not expressed 1 3 2 0 0 6 1 1 2 0 1 5
leaf blotch development Expressed not forecasted 0 0 0 0 1 1 0 0 0 0 0 0 % accurate forecasting 94 77 78 100 86 87 94 92 80 100 83 90
Discussion and conclusion
A validation process on the « Proculture » model in the G-D of Luxembourg occurred during year 2000 and 2001. The peculiarity of the simulation model is its ability to analyze interactions between winter wheat development and progression of M. graminicola on the already developed wheat leaves, to simulate disease progression in the crop and to allow users to experiment the model through a web interface with their own input data in order to get advice on individual fields. This decision making tool helps to find the optimum time of fungicidal supply in fields i.e. when high risk of early F3 infection occur. Fungicide application before GS-32-37 stages (Zadocks et al., 1974) would have provided efficient protection of the upper leaves (F2 and F1). The model will be in validation in several experimental plots in the G-D of Luxembourg for three years ago.
References
ElJarroudi M.,Tychon B.,Maraite H.Florence ESA 2001. 63-64. Hunter T.,Coker R.R.,Royle D.G.1999.Plant Pathology. 48 : 51-57.
Moreau J-M.,Maraite H.2000.Bulletin OEPP/EPPO. Bulletin 30 : 161-163. Moreau J-M.,Maraite H.1999.Aspects of Applied Biology. 55 : 1-6.
Shaw M.W.,Royle D.G.1989.Annals of Applied Biology. 115 : 425-442. Zadocks J.C.,Chang T.T,Konzak C.F.1974.Weed Research 14 : 415-421.
C Everlange B A C Reuland B A
