Simulation of damage in winter wheat caused by the grain aphid Sitobion avenae. 2. Construction and evaluation of a simulation model

Abstract

To evaluate the relative importance of various components of damage caused by grain aphid (Sitobion avenae F.) populations in winter wheat, a simulation model of crop growth and development is combined with a model of aphid injury. The model applies to the time interval from flowering to ripeness which constitutes the main period of grain aphid immigration and development in winter wheat in the Netherlands. The crop model describes crop growth and development as a function of the prevailing weather and the available amount of soil nitrogen and consists of sink-source relations and distribution functions for carbohydrates and nitrogen.Injury by S. avenae affects crop growth both directly and indirectly. Direct effects on growth are due to aphid feeding. Indirect effects are caused by the aphid excretion product honeydew which affects leaf net carbon dioxide assimilation. Alternative hypotheses on the nature of the direct effects are formulated. Inputs to the model are average daily temperature, daily global radiation, the amount of nitrogen in the soil and the density of the aphid population. The major output is grain weight.The accuracy of the model is assessed by visual and statistical comparison to field data. The accuracy of both crop and damage model is satisfactory except for the final part of the growing season. Then, insufficient information on processes involved in leaf death and the termination of phloem transport to the grains results in overestimation of the rate of grain filling.The consequences of the lack of detailed information on the relation between environmental factors and the effect of honeydew on leaf carbon dioxide assimilation are assessed in a sensitivity analysis.

Simulation of damage in winter wheat caused by the grain aphid Sitobion avenae. 3. Calculation of damage at various attainable yield levels

“…avenae population is calculated using a computer model described previously (Rossing, 1991). With this model, growth and development of winter wheat during the post-anthesis phase, i.e.…”

“…All data have been collected in experiments designed to evaluate the effect of the rate of nitrogen fertilizer application on crop production. Six of the data sets used, BOUWING84, EEST83, EEST84, PAGV1, PAGV2 and PAGV3, have been described in an earlier paper (Rossing, 1991). Three additional data sets, HELECINEl, HELECINE2 and HELECINE3, pertain to experiments carried out in north Belgium (Anon., 1984;Anon., 1985).…”

“…Aphid feeding is assumed to cause a decrease of the rate of carbohydrate and nitrogen accumulation in the grains equal to the rate of uptake of these components by the aphids. This assumption which has been referred to as hypothesis IV previously, appears the most appropriate for describing aphid feeding in view of experimental evidence (Rossing, 1991). Honeydew contributes to damage as it increases the rate of maintenance respiration and decreases the rate of carbon dioxide assimilation at light saturation.…”

“…In an earlier paper (Rossing, 1991), a systems approach (de Wit and Goudriaan, 1978;Rabbinge et al, 1989) was taken to quantify damage by S. avenae in winter wheat. A simulation model of growth and development of winter wheat from flowering to ripeness was combined with a model of injury by S. avenae.…”

“…Evaluation of the crop growth model was carried out for attainable winter wheat yields ranging from 5000 kg ha -I to 10 000 kg ha -I. The injury model was evaluated at the higher yield levels only due to lack of data at other yield levels (Rossing, 1991).…”