b'increasing percentage of greenhouses with heating belong to highly technical companies, usually heating with natural gas during the day, taking advantage of the combustion gases (CO2) to enrich the environment for plant growth in well isolated struc-tures. Especially these companies have clear commitments to limit the use of fossil energy and seriously search for alternative sources, such as biofuel or new applications of solar energy. WATER AND FERTILISER USEGreenhouse horticulture is situated in the most arid regions of Europe, making it necessary to extract as little water as possible from the available aquifers. In general, the profitability of water, i.e. the obtained yield per m3 of irrigation water, is far higher in greenhouses than in other agricultural crops. All greenhouses have drip irrigation, and over 80% of the crops grow in a soil covered by a thick layer of sand, where the water immediately penetrates to the rooting zone. Under plastic, evaporation is much more limited than in open air. Water used for irrigation is measured, so the amount and concentrations of fertilizers can also be properly dosed.Despite the advantages offered by irrigation systems in greenhouses, there is a clear challenge to optimise water andChameleon, in the middle of the greenhouse area. fertiliser use. Observing the general practices of the growers in Almeria, it can be estimated that, approximately, 30-35% of water might be spared by introducing modern equipment andGRAPH 1. IMPLEMENTATION OF IPM INmeasuring methods. An important saving can be achieved by10000 SWEET PEPPER IN ALMERIAthe replacement of the simplest, and cheapest drippers by pres-sure-compensated drippers, to obtain a much more homogene-ous distribution of the irrigation. Furthermore, the timing and the volumes of irrigation can be optimised by measuring the8000needs of the plants. Until some years ago, growers only disposed of mechanical sensors, such as the tension meters, that had to be checked continuously to be useful as a guidance tool. Nowadays, there are more and more electronic devices that enable an ade- 6000quate measurement of the humidity conditions in the root zone, allowing real time monitoring in computers and mobile phones. Irrigation programmes can be managed at a distance through internet. At present, the percentage of growers using these new4000techniques, less than 10%, is still small. However, these devices are increasingly user-friendly. The growers that start to use them experience a clear economic benefit, by saving water and fertilizers, and obtaining better crop conditions and, ultimately,2000higher yields. These direct benefits make that the adoption of optimised irrigation techniques may soon boost to a large scale.PEST CONTROL, PESTICIDE RESISTANCE 0Pest management in greenhouse horticulture is more com- 05-06 06-07 07-08 08-09plicated than in most open field crops, due to the micro-cli- Chemical Control (Ha) IPM, with Biological Control (Ha)mate conditions, which are almost permanently favourable for pests and diseases. Furthermore, most crops are vulnerable to insect-transmitted viruses, causing considerable crop losses.insecticides were banned, and all treatments were limited to a In the past, this has led to an intensive pesticide use and, con- minimum in order to respect the bumblebee workers. After this sequently, to resistance of some pests to all available activechange, there have never been any significant residue problems ingredients. Finally, excessive chemical treatments, inevitably,on harvested tomatoes. gave rise to high concentrations of residues on the harvest, fol- Biological pest control first became important in sweet pepper lowed by commercial rejection of several Spanish horticulturalcrops, where the most important pest was thrips, Frankliniella products on the European market. However, due to the mas- occidentalis. Thrips are responsible for direct damage on the sive adoption of biological control as the basis for Integratedfruit, but, most importantly, for the spread of virus (TSWV) that Pest Management (IPM), the problem of pesticide residues onmay devastate entire crops. The low tolerance levels for this pest horticultural products from Southern Europe have now beenhad led to increasing pesticide use, with little effect because of overcome, guaranteed by an extremely strict control at all levels. the complete resistance of the pest against all available insecti-In the South of Europe, the first important step towardscides. Biological control of thrips is based on the introduction of IPM in greenhouses was the introduction of bumblebees forpredatory mites (Amblyseius spp.) and bugs (Orius laevigatus), pollination in tomato crops, around 1995. Natural pollinationcomplemented with other natural enemies against other pests, as by bumblebees was so profitable that growers were obligedwell as with the use of some sufficiently selective pesticides. This to adapt their pest control system, making it compatible withwas already working for a decade in the glasshouses of Central these beneficial insects. For the first time, most broad spectrumEurope, when the first large scale application became successful EUROPEAN-SEED.COMIEUROPEAN SEED I 41'