Crop diseases have always been the farmer’s nightmare because of their destructive impact on crop yield and quality. FAO estimates that annually between 20 to 40 percent of global crop production are lost to pests costing around $300 billion for the global economy. It is therefore no surprise that a staggering amount of money and energy is equally spent every year in the attempt to eradicate them and limit crop losses.
Classical solution to pests and disease include the use of pesticides and the adoption of agronomical measures , such as variety selection or a larger inter-row spacing to prevent attacks. In the case of pesticides, chemicals against fungi, bacteria, virus and insect pests are applied to the crop to prevent diseases to destroy harvests and to preserve yield.
However phytosanitary treatments should be carefully planned by selecting the best timing of application and the type and dose of the chemicals to be used, in order to decrease environmental and human health impacts and to reduce phytosanitary costs for the farmer.
In order to do this the actual risk of disease need to be evaluated with precision, by integrating different information. This integration can be illustrated by the disease triangle, a classical paradigm of plant pathology. This conceptual model shows that for a disease to actually develop the simultaneous presence of three factors is needed : a susceptible host, a virulent pathogen, and an environment favorable for disease development.
Plant Disease Triangle
Whereas it can be relatively easy to determine whether a crop pathogen is present in a certain area, the evaluation of the susceptibility of the crop and the favorability of the weather for the disease can be more complex. Each disease responds to specific weather conditions, and attacks the plant during specific vulnerability windows, which often correspond to particular phenological phases. For example, grey mould (botrytis cinerea) prevalently infects dead plant tissue. In grapevine it penetrates into senescing flowers at the end of flowering but only develops at a later stage, between veraison and harvest. Botrytis will develop faster under warm and humid conditions, like many fungi. Powdery mildew on the other hand, can produce primary infections on green parts only before veraison, due to its inability to penetrate old and thickened leaf tissue. It also grows faster in warm and humid conditions, but is hampered above 26-28 degrees and when free water is present on the leaf surface.
The complexity of these interactions can make it difficult to evaluate actual disease risk and take rapid and effective phytosanitary decisions. In order to help farmers with this challenge and protect their crop and decrease economic and environmental costs, ITK has developed different solutions based on current research, that have completed existing tools for irrigation and fertilisation.
ITK smart solutions for crop disease management
Soya bean and Corn
Cropwin, the DSS for fertilisation and irrigation of annual crops, has a new feature for the prediction of disease risk for soya and corn. This feature effectively combines long term weather forecasts and crop phenology to predict the first symptoms of Northern corn leaf blight and Gray Leaf Spot for corn and Frogeye and White Mold for soybean. The indicator follows a colour code (red : very likely, orange : likely, green : not likely) and predicts risk up to 6 weeks in the future to allow a better planning of plant protection. This indicator is easy to interpret and can be easily adapted to local conditions by ITK. Its flexibility and modularity make it possible to adapt it for new situations and crops.
Grapevine
Vintel has now integrated a new tool for forecasting the first symptoms of powdery mildew. The timing of powdery mildew appearence is very important because it determines the beginning of treatments which are then often repeated at regular intervals. An earlier than needed start of treatments implies a larger quantity of chemicals and a more expensive phytosanitary budget whereas a later than needed start might lead to heavier impacts of the disease on final crop yield. It is therefore important to estimate precisely the beginning of primary infections.
To do so, Vintel has implemented the Gubler Thomas indicator for the forecast of powdery mildew appearence. This indicator has been developed by UC Davis and it has been established as a longterm reference for growers in the western US.
Its popularity and widespread use are validation of its usefulness for phytosanitary planning. The Gubler Thomas indicator is now automatically calculated by Vintel, and can be coupled with a local weather station or/and a gridded weather data for your area, which provide plot specific data and forecast. Predicted powdery mildew pressure is associated with recommendations concerning the spray schedule for 4 fungicides groups. The integration of weather forecast, disease risk and crop phenology alows a holistic vision of the vineyard and a more effective and sustainable crop management.
Banana
Sigatocare is a decision support system for the phytosanitary management of black leaf streak (BLS) of banana tree. This disease is a serious concern for banana growers all over the world, because it decreases yield and shortens the post-harvest green life of banana fruit, making banana export difficult.
ITK has collaborated with the french research institution CIRAD to implement the CIRAD indicator for BLS, already used by growers and agronomist in Africa and South-Central America to decide product application. The indicator, expressing disease pressure with a score is coupled with other information such as the timing of the last treatment to return a global risk level (high , moderate, low).
This indicator, is actually based on observation of symptoms and requires frequent monitoring of banana trees by farmers. ITK has produced a user friendly app that makes monitoring easy and indicator calculation immediate and visually explicit through dynamic plots. Product application timing and type are also displayed allowing a general view of the phytosanitary status of the plot.
Agronomist and scientific editor