Evaluation of models to predict take-all incidence in winter wheat as a function of cropping practices, soil, and climate

Abstract

The incidence and severity of take-all, caused by Gaeumannomyces graminis var. tritici (Ggt), in susceptible crops depend on climate, soil characteristics and cropping practices. Take-all can be controlled by modifying crop rotation, crop management and fungicide treatment. When available, fungicides are used as a seed treatment and are partially effective. There is currently no reliable method for helping farmers to optimise their choice of cropping system to improve take-all control. In this study, we defined 16 models, based on various mathematical functions and input variables, for predicting disease incidence in a wheat crop as a function of soil characteristics, climate, crop rotation and crop management. The parameters of these models were estimated from field experiments carried out at six sites in the north of France over a ten-year period. The root mean squared error of prediction (RMSEP) values of the models were estimated by cross validation and compared. RMSEP was in the range 16.34-65.93% and was higher for the models based on multiplicative functions. The lowest RMSEP value was obtained for a dynamic model simulating disease incidence during the crop cycle and which included among input variables the percentage of diseased plants determined at GS3

Economic Analysis of Summer Fallow Management to Reduce Take-All Disease and N Leaching in a Wheat Crop Rotation

“…The distribution of the probability of occurrence of one particular Fsem30 value (out of three) plays a key role in the assessment of the impact of take-all risks. In absence of sufficient experimental evidence, we assume that (70, 85, 100) Associated probability (P i = Prob(FSem30 = f i )) P 1 1/6 0 1/3 Uniform P 2 = 1 − P 1 − P 3 1/3 0 1/3 P 3 = P 1 1/6 0 1/3 the central value of the range given in Ennaïfar et al [13] for each management system is associated with a probability P 2 = 2/3 and that the probabilities that the two extreme values occur are equal to P 1 = P 3 = 1/6. Economic indicators (expected utility, mean and standard deviation of profit, minimum subsidy, and risk component) for each management system under the base assumptions are presented in Table 5.…”

“…Ennaïfar et al [13] have developed several models to predict the incidence of take-all disease on winter wheat as a function of crop management, soil characteristics, and climate. The models have been built and validated on a large database, which includes data on the area of study.…”

“…It has been shown that the use of a disease measurement at a very early stage of the plant cycle greatly improves the prediction of the models. In our simulations, we chose StatL1+, an additive static model with one of the best predictive value [13]. The disease score (Fsem30) is the percentage of plants with diseased seminal roots at the leaf sheath erect stage of the crop cycle (GS30).…”

“…Eight management practices (four summer fallow management, including two types of cover crop and two levels of input intensity) are simulated. The epidemiological model is based on Ennaïfar et al [13] from which we infer the yield loss associated to various disease ratings and summer fallow management options. The simulated distributions of climate-related impacts on yield and take-all severity are then introduced in an economic model that determines the optimal management system on the basis of expected utility.…”

Effect of host and inoculum patterns on take-all disease of wheat incidence, severity and disease gradient

“…Following observations that yield loss was reduced more by the lateral distance between the seed and the inoculum than by the horizontal distance between seed and inoculum (Kabbage and Bockus 2002), a model showed that when wheat is direct-drilled, planting the seeds exactly between rows of the previous year's wheat crop could result in yield losses less than 40% of the yield losses predicted in the case where seeds are exactly on the row of the previous year (Garrett et al 2004). As there is no efficacious fungicide available to control take-all, it is particularly important to consider all possibilities to reduce disease development, even by a small amount, and combine several partially efficient control methods in an integrated approach (Lucas 2006;Ennaïfar et al 2007). Such methods include soil cultivation (ploughing can bury the infected residues (Colbach 1994)).…”