* According to van Lenteren (2000) and in the greenhouses, we can restore previously used forms of natural & biological control but several other alternatives for conventional chemical pest control methods can be implemented such as mechanical, physical, genetic, pheromonal & semiochemical control (Table 27.1).
* In the development of IPM programs for greenhouses, we have based our work on the following IPM philosophy:
IPM is a durable, environmentally & economically justifiable system in which damage caused by pests, diseases and weeds is prevented through the use of natural factors which limit population growth of these organisms. If necessary supplemented with appropriate control measures. A control program will only be considered truly IPM if it involves a number of natural enemy species.
* Successful IPM programs for greenhouse crops have a number of characteristics in common such as:
1) their use was promoted only after a complete IPM program had been developed covering all aspects of pest & disease control for a crop;
2) an intensive support of the IPM program by the advisory/extension service was necessary during the first year;
3) the total costs of crop protection of in the IPM program were not higher than in the chemical control program; and
4) non chemical control agents (e.g. natural enemies, resistant plant material) had to be as easily available, as reliable, as constant in quality and as well guided as chemical agents.
Current situation in greenhouse IPM:
* IPM can be used in all main vegetable crops. In Netherlands, > 90% of all tomatoes, cucumbers, sweet peppers & eggplants are produced under IPM. Worldwide, 5% of the greenhouse area is under IPM and there is potential for this to increase to about 20% of this area in the coming 10 years. The development of the area under IPM is presented in Fig. 27.2. Until the year 2000, most IPM took place in European greenhouses, but currently, application of IPM is growing very quickly in Asia.
* An example of an often-used IPM program is in one for tomato in Europe. It involves 10 or more of natural enemies and various other control methods like host plant resistance, climate control and cultural control (Table 27.2).
* At a first glance, such an IPM programs may look complicated but after a year of experience & support from the provider of biological control agents, growers are able to carry it out.
* A recent development which gave a strong stimulus to the application of IPM is the use of bumbel bees for pollination because chemical control can no longer be used as it kills the pollinators.
* Detailed examples of IPM programs for vegetables used in different parts of the world are presented in Albajes et al. (1999).
* Development of IPM for ornamentals is more complicated than for vegetables. The first problem is that many different species and cultivars of ornamentals are grown. In western Europe, for example, > 100 of cut flowers & 300 species of potted plants are cultivated. Each of these species/cultivar may need specifically designed IPM program,
and these are applied on much smaller areas than those for vegetables, which results in higher costs. Other problems for implementation of IPM in ornamentals are that:
1- more pesticides are available than for vegetables and higher residue levels are accepted, and
2- the whole plant is marketed, instead of only the fruits, so no leaf damage is allowed .
IPM was applied on > 10 % (600 ha) of the total greenhouse area planted with flowers & ornamentals in 1998 in the Netherland. Commercially used IPM programs for ornamental crops are presented in Gullino & Wardlow, 1999. Worldwide, it is estimated that 100 ha of ornamentals are under IPM.
How has implementation of IPM in greenhouse been realized?
we have experienced during the past decades that implementation of IPM in greenhouses in some crops and regions (e.g. vegetables in
temperate climates) is much easier than in others (vegetables in semi-tropical climates and ornamentals in all climates) because of diffetrencesin attitudes of growers, in climate, in greenhouse design, in cultural methods and in composition of the pest complex. Therefore, only one example of a specific IPM program was given above.
* Technically, implementation of IPM is not different from that of chemical control. At the introduction of first IPM program for a new crop, special attention should be paid to extension. The degree of knowledge makes acceptance of more complicated IPM programs initially difficult for the grower. IPM methods are rather new and demand a different attitude based on the principle to introduce a natural enemy or pesticide only when the pest insect is present & expected to lead to economic loss.
* Experience in the Netherlands has shown that the amount of application of IPM is strongly related to the activity and attitude of extension personnel.
* If governmental extension service is weak, implementation of the IPM will be very difficult due to aggressive approaches from pesticides salesmen. Also, all participants in an IPM program must be receptive to new developments and willing to implement them.
*When growers, extension agents and researchers agree that use of IPM is as cheap as chemical control and that production and delivery of alternative control methods is reliable, IPM can be applied in a similar way as chemical control and becomes a normal commercial affair.
* The following factors may hamper introduction of IPM programs:
1) Funding of research in IPM; 2) Growers’ attitudes; 3) The viewpoint of chemical industries; 4) The role of governments, food processors and retailers; 5) Registration and environment risk assessment.