Crop monitoring techniques pests and diseases

Some of the gains in agricultural production under local current conditions or expected with higher production efficiency or change in climatic conditions could be cancelled out by the losses caused by pests or diseases (McCarthy et al. 2001; Cannon 1998). Even though appropriate agricultural practices and technology might help to control pest populations or diseases, these measures increase the overall costs of production and place further stress on the environment where pesticides or fungicides are used (Chen and McCarl 2001). In addition, some of the pest and disease control techniques (e.g. deep ploughing) could conflict with efforts to conserve soil water through minimum tillage systems. Similarly, the introduction of genetically modified crops remains problematic in EU countries, and it raises a lot of questions in its own right (Gutierrez and Ponsard 2006).

In the case of pests the ontogeny of poikilothermic insects is controlled mostly by temperature (with other weather factors reducing or enhancing survival rates), and this fact has been utilized by agrometeorologists and phytopathologists for several generations to increase crop protection efficiency. A wide variety of modeling techniques (Guisan and Zimmermann 2000) are used in ecology studies (Logan et al. 2006; Beaumont et al. 2005) and by farmers or consultant companies as part of expert or operational warning systems (Grunwald et al. 2000; Hijmans et al. 2000; Aggarwal et al. 2006a). Models of different complexities have also been used to determine the probability of a particular pest's establishment in a given locale or in the case of the unintentional introduction of alien species (Morrison et al. 2005; Gray 2004; Rafoss and Saethre 2003; Jarvis et al 2001).

Models capable of estimating the spatial extent of a climatically suitable area for a particular pest allow us not only to identify the species' current potential distribution but also to assess which regions will be climatically suitable under future climate scenarios, tteses models could be successfully used to monitor the development of the particular pest stage at a given locale or to provide farmers with timely information on the present status of the pest development, tte latter could be done on the local scale (http://www.srs.cz/pas/mury/zavijec/index.php, 2006) or in the form of spatialized maps available to farmers in the given area (http:// www.pestwatch.psu.edu/sweetcorn/tool/tool.html, 2006). Even on a larger scale monitoring can be useful, ttis is the case with locusts, a well known and highly destructive pest in many developing countries, which is sensitive to rain distribution during the early season. Monitoring on an international scale is necessary to establish an effective warning system so that appropriate measures can be taken, tte fact that this aspect is underdeveloped at present can be seen only too clearly from the past events in the Sahel zone.

Similar monitoring techniques have been or are being developed for various diseases as well, but in many cases the interaction with climatic factors is much more complex and less understood than in the case of pests.

Recent studies (Trnka et al., 2007) have shown that the pest-crop-climate relationship is dynamic and that species that have not been considered important in specific regions in the past might become a major problem on account of climate shifts and could expand to new regions. One example is the observed occurrence (with apparent damage to the crop) of the European corn borer (ECB) in the Czech Republic between 1961 and 1990 and between 1991 and 2000 (Fig. 10.10). Whereas the climate mapping results suggested two potential niches for the pest between 1961 andl990 (Fig. 10.10a), the bulk of the ECB population was concentrated in the south-east of the country, not least because of the very low grain maize acreage in the other region, tte decade from 1991 to 2000 saw a significant expansion of ECB (Fig. 10.10). tte invasion of the pest has been blamed on the general increase in grain maize acreage, the overall decrease in the use of insecticides, the widespread use of minimum tillage technologies, and a general decline in the quality of farm-

Fig. 10.10. Climatically suitable areas for the European corn borer (ECB) in the Czech Republic in terms of the climate suitability index for the monovoltine populations (CSj). ^e CSI values > 0.71 mark regions with suitable conditions and those with CSj > 0.85 those with excellent conditions. ^e ECB might also be found in unusually warm years in the area marked in green if maize is present, ^e CSj value is shown for 1961-1990 (a) and 1991-2000 (b). ^e dots represent sites where the ECB occurrence in maize was observed under field conditions.

Notes: For better visualization Fig. 10.6 includes the whole territory of the country (excluding areas above 800 m above sea level) rather than the arable land only.

Fig. 10.10. Climatically suitable areas for the European corn borer (ECB) in the Czech Republic in terms of the climate suitability index for the monovoltine populations (CSj). ^e CSI values > 0.71 mark regions with suitable conditions and those with CSj > 0.85 those with excellent conditions. ^e ECB might also be found in unusually warm years in the area marked in green if maize is present, ^e CSj value is shown for 1961-1990 (a) and 1991-2000 (b). ^e dots represent sites where the ECB occurrence in maize was observed under field conditions.

Notes: For better visualization Fig. 10.6 includes the whole territory of the country (excluding areas above 800 m above sea level) rather than the arable land only.

ing practices, ttese changes correlate with the overall social and economic reforms started in 1989 that led to a decade-long crisis in the agriculture sector.

tte maps suggest, however, that the underlying cause of the ECB expansion was a major increase in the size and quality of the prime niche area (Fig. 10.10) and that eradicating the ECB populations (once they have become established) is virtually impossible, ttis claim is based on the past 70 years of experience with the pest in the south-east corn-growing region or the US Corn Belt, where despite all efforts the pest has never been eradicated. Farmers therefore have to adopt new strategies to keep the pest population below critical levels (e.g. appropriate crop rotation and tillage practices, timely use of insecticides or introduction/selection of resistant varieties) rather than invest in eradication programmes. In all cases the existence of real time monitoring programs allows more effective treatment of the exposed crops.

New technologies permit the monitoring of crop conditions on a much smaller scale. A related new emerging technology is "precision farming", ttis technology is still under development, currently applied only rarely and related to new technologies such as remote sensing, GPS and GIS. Because of high costs it is still available only for high-input farming (Pedersen et al. 2004; Godwin et al. 2003). It is based on observing spatial variabilities of several factors in crop fields, such as nitrogen content of leaves, drought status, disease occurrence or in-field yield variation. Using the observed information the farmer can apply measures based on the actual site-related status, considering field-level variations, ttis can significantly decrease costs for fertilizers and chemicals and enhance crop yield and productivity. Applications are also known for sprinkler irrigation of annual crops, applying water according to spatially changing soil conditions, tte related equipment is still costly and not appropriate for low-input farming and small farms, but on a larger scale and on an institutional basis such technologies might be available at lower cost in the future following further development. Locally adapted crop management of low-input systems may use other options to precisely adapt management to spatially changing soil and crop conditions. In small, not technologically driven farms such options tend in any case to be based on the experience of the farmer.

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