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  • Microorganisms for the treatment of roots:

    Mycorrhizal fungi, Trichoderma and beneficial bacteria (PGPR)

    This section gives answers to frequent questions about the application, efficacy, compatibility, durability, quality and safety of our microorganisms for the treatment of roots.

    How often should the microorganisms be applied and in which quantities?

    There is a general rule of thumb: Better small amounts often than one big amount once. The aim is to maintain stable populations in the soil that protect the roots over longer periods of time.

    Free living microorganisms, such as rhizobacteria and Trichoderma, frequently establish big populations initially that can collapse again in the course of the growing cycle. In this case the inoculum should be applied several times.

    Reapplying small amounts periodically over extended periods of time also helps to maintain a divers array of beneficial strains. After several species of microorganisms have colonized the root surface successfully, their distribution patterns start to shift. A species that is very dominant at the beginning may fall out completely later. Awkwardly, it may be precisely this species which renders especially valuable services to the crop at a more advanced stage of its development, for example throughout the highly demanding moment of fruit growth.

    The situation is slightly different in microorganisms that are closely associated with the tissue of plant roots, such as mycorrhizal fungi or rhizobia inside root nodules of legumes. Plants that were inoculated well and entirely after germination retain these symbiotic partners until the end of there lives. Reinoculating does generally make less sense.

    Reapplication of EndosporTM

    Positive surprises are not uncommon when reapplying endomycorrhizal fungi. Vineyards and orchards that are several years old often profit from a fresh mycorrhization by EndosporTM. The benign effect of this "refresh" seems to be linked to the competition that occurs between different mycorrhizal species. After the novel application high performing strains replace species that are less efficient in parts of the root system.

    The reapplication should take place at a time of the year when roots tend to grow. In temperate climes this happens in spring. The best moment in tropical and subtropical climes is at the end of the rainy season or - in irrigated crops - at the end of winter

    Should the microorganisms be multiplied before the application?

    Some users propagate the organisms prior to application. Typically, a commercially available spore product undergoes a reproductive process under non-sterile conditions for several days. The aim of this "enrichment" is to generate more infective material for the treatment of plants. Also, once the microorganisms have advanced from spores to colonies or mycelia, they are able to colonize the root surface more immediately.

    We agree that this reproduction can be advantageous at times. Nevertheless, we think that it is not justified in the face of readily available inocula that are technically mature and conveniently priced. Considering the long list of possible disadvantages, we do not recommend to multiply the organisms prior to application.

    The growth medium consists of an energy source (molasses, dextros...), nutrients (N, P...) and other sources of organic material (compost, fibers..). Sometimes these components may not be digested completely by the microorganisms, for example when the fermentation is being interrupted. Applying these components to the plants can have unforeseen consequences.The growth medium consists of an energy source (molasses, dextrose...), nutrients (N, P...) and other sources of organic material (compost, fibers...). Sometimes these components may not be digested completely by the microorganisms, for example when the fermentation is being interrupted. Applying these components to the plants can have unforeseen consequences.

    The additional investment in time and work can only be justified by the substantially improved efficacy of the microorganisms. This criterion is rarely being fulfilled in the context of a modern, economically run plant production.

    Possible disadvantages of multiplying prior to application

    Undigested residues of sugar can serve as a readily available energy source for pathogens that are already present in the crop, such as Xanthomonas or Phytophthora. In contrast to the new-comers, these established organisms are well adapted to the environment and thus able to use the sugar immediately for an explosive growth before they can be suppressed by the beneficial microorganisms. This danger is especially real for leftovers on the leaves after spraying.

    The additional input of nitrates and phosphates can cause imbalances in a highly fine-tuned plant production. Above all care should be taken with hydroponic and semi hydroponic production systems. Their computer controlled, highly optimized nutrient inputs can become imbalanced by the unintended import of an additional nutrient source. There is anecdotal evidence that microorganisms that are multiplied in this way can enter into competition for nutrients with the plants. This cannot happen when applying our high-tech products.

    When crude plant material is used as the source for carbohydrates it can become the avenue for the introduction of pathogens because they are multiplied just as all other microorganisms in the mixture. These materials should be exposed to the high temperatures of a composting process first, in order to kill pathogenic fungi and bacteria. In contrast, the propagation of beneficial rhizobacteria and Trichoderma does not allow for high temperatures.

    This last point leads to the following general consideration: Good commercial inocula consist of blends of pure strains that are produced separately under sterile conditions in the highly controlled environment of industrial bioreactors. This kind of incubation precludes the co-production of undesired microorganisms. All conditions that are important for the growth are strictly controlled, so that the strains do not loose their desired properties. Leftovers of growth media are limited to a minimum. All these factors lead to consistently high quality that is being monitored constantly according to scientifically objective criteria. This is crucial because it is the only way to assure that good results obtained from applications in the field in the first year can be achieved again in the following years.

    The artisanal reproductive process harbors a whole range of uncertainties. The duration of the fermentation and the ambient temperature under which it takes place tend to vary. As a consequence, dramatic changes may occur in the resulting species composition, the remains of the growth medium and the application properties. Since many microorganisms grow together, some species might be suppressed by competition and fall out all together. Mycorrhizal fungi, for once, cannot be reproduced in this way and most likely do not survive this process. The efficacy of the species that do survive may suffer at least partially. Thus, the reproduction process can result in highly variable end products which perform differently when applied to plants. This great number of unknowns has the potential for surprises which can distort planning schedules and time tables and in the worst case cause loss.

    Is there an overdose for the application of microorganisms?

    The fertilization with an overdose of mineral salts can cause the "burning" of the plants. This is not the case for the application of microorganisms. In other words, they either do their job or die. An overdose does not exist in a purely technical sense. Rather, the art of finding the right application rate consists in achieving effects through a sufficient amount of product and within an adequate budget.

    What is the right amount of water for the application of the microorganisms?

    Our products are fine powders or granulates. Some applications require them to be blended into potting mixes or to be mixed with the seeds. Often though they are mixed with water and sprayed or injected through the irrigation system.

    For example, the product BactivaTM is often applied at a rate of 30g per 10L of water. It is important that the spores of the microorganisms are drenched into the root zone. On the other hand, the water absorption capacity of the substrate should not be surpassed, in order to avoid flushing the spores out (for example by dripping through the bottom of irrigation trays).

    From a biological perspective it is not important how much water is being applied, as long as there is enough water around for spore germination. In other words, the main function of the water is to serve as a vehicle. The aim is to introduce the spores as completely as possible into the root zone. The amount of water depends primarily on the application method and the equipment. It should allow for an even distribution of the product in a given production unit (germination tray, pot, raised bed, field or orchard).

    Differences between foliar/soil applications

    The amount of water should be well calibrated when applying biological products, such as Bacillus thuringensis, Beauveria bassiana or Metarhizium anisopliae to the leaves of the plant. The efficacy of these products depends on the degree of surface covered. At the same time, a high concentration of spores is crucial to a good "hit score" when trying to reach all pathogens on the leaves.

    The success of applications in the root system does not depend so much on the concentration of the spores in the immediate proximity of the root and its coverage of the surface. These bacteria and fungi can spread by forming colonies and mycelia. They are saprophytes and can make use of organic matter in the soil to grow towards the pathogens that they control. Conventional wisdom has it that this is virtually impossible for the spores of many microorganisms that live in the nutrient deficient cuticle of the leaves.

    Is it necessary to adjust the pH of the water prior to mixing it with microorganisms?

    All microorganisms thrive at a specific pH range that boosts their growth and efficacy. This is why some suppliers recommend adjusting the pH of the water before introducing the microorganisms. We do not support this view because the microorganisms chosen by us can cope with irrigation water that is somewhat acid or alkaline as long as this pH lies within the limits tolerated by plants. Even if the range is not in the optimum, they do not suffer permanent damage and for this reason there is no need to adjust the pH of the water when mixing.

    Ultimately, it is the pH that the microorganisms encounter in the rhizosphere and the soil that affect their performance. Our strains tolerate more extreme pH-values than the plant. This explains why inoculated plants frequently outperform untreated plants on extremely acid or alkaline soils. The prime example is the successful reforestation of abandoned US mines with the help of the ectomycorrhizal fungus Pisolithus tinctorius after years of futile attempts without the fungus.

    When does it make the most sense to apply microorganisms?

    Applying beneficial microorganisms at regular intervals can improve production success particularly when negative soil properties harm the development of plants and soil organisms. They stimulate the growth of roots that have been damaged by transplant, fight with disease or suffer from soil compaction by boosting the development of the healthy parts while suppressing the pathogens.

    Experience shows that it is uniquely beneficial to introduce microorganisms in soils that have been cultivated with conventional methods. Usually, the plants respond with an improved nutrient uptake, enhanced growth and higher yields.

    Applying microorganisms makes a lot of sense when it is not conceivable that sufficient amounts of beneficial strains and species reach the rhizosphere by natural processes. This is especially true for endomycorrhizal fungi which have spores with large diameters. Normally they are not carried by air and thus absent from germination trays.

    Mycorrhization

    Seedlings that are germinated in peat moss or similar substrates usually cannot form mycorrhizae without the application of mycorrhizal spores. However, treating the plant with the fungus at an early stage gives the fungus the opportunity to invade the whole root area. In the process the fungus undergoes a maturing process just like the plant. Finally, at the moment of transplant, a well developed mycelium supports the plant to overcome the transplant stress. Nonmycorrhizal transplants normally come into contact with mycorrhizal fungi in the field sooner or later. Nevertheless, a late mycorrhization means that they loose out on an important head start at a crucial early moment of the growth cycle.

    There is a huge diversity of crops that benefit from mycorrhization. However, those crops that give high yields over many years, such as vineyards and orchards, are especially attractive. The cost-benefit analysis is unambiguous and they should be treated early on and possibly several times. The investment in Endospor is minute as compared to other costs of crop production and the possible gains. The calculation is different for short lived crops, such as lettuce where the costs of mycorrhization can easily outweigh the benefits. In this case a field trial should give a clearer picture.

    Why do not all growers and agronomists already apply microorganisms?

    The worldwide use of microorganisms in plant production is steadily climbing. Their potential to complement or substitute for chemical fertilizers and plant protection products has been proven scientifically. However, their use of microorganisms is still in its infancy when compared to the predominance of chemicals. The reasons are manifold and sometimes subject to controversial discussions.

    Many suppliers of biological plant protection products argue that users and lawmakers are being influenced by the intense lobbying of the financially powerful chemical industry. Manufacturers of biological alternatives too have increased their lobbying activities over the past few years. However, these outfits are for the most part small, local and service orientated. Their lobbying efforts tend to pale in the face of the ubiquitous presence of multinational chemical companies.

    Small manufacturers of biological products cannot pay for the costly registration processes of plant protection products that are set by the high standards applicable to the chemical industry. At any rate this hold true for the present initial stage with the absence of big and lucrative markets that would justify these investments.

    As a result, suppliers of "soil amendments" or"plant fortifiers" have to limit their claims to vague statements about the mode of action and advertise any aimed for pesticidal effects as "side effects". Once corned into this category, effective products are put together with dubious "snake oils" that do not pass a thorough scientific efficacy test.

    "Conservative" users

    The often quoted assertion that many growers and farmers are "conservative" and thus are not easily convinced by new developments does not explain anything. The sector has been shaped by all those technological trends that have transformed other branches of the economy, such as industrial rationalization, computerization and globalization. Neither is there a shortfall of regular crisis moments that spur change, like the increase of energy and fertilizer costs or the ever more limited portfolio of plant protection products due to more stringent legal restrictions and the emergence of pest resistance.

    The buyer cannot rely on commonly accepted standards for this nascent industry when choosing between different microbial products. Even the concentration of the stated ingredients can only be verified by costly analysis. This results in a buyers beware marketplace. By this count some few "lemons" of doubtful quality can harm the reputation of the whole industry, especially if fraudulent suppliers exaggerate claims for a quick buck.

    Over time, the increasing interest and turnover unleashes a growth in high quality products and the consumer's brand awareness. We look with confidence into the future and believe that new technologies that create real value will prevail eventually.

    Is it possible to use soil-borne microorganisms for the control of leaf disease or for foliar fertilization?

    Mycorrhizal fungi cannot grow on leaves. They have to be applied to the roots. This is different for many free living bacteria and fungi of the rhizosphere. Most can grow in the aerial parts of the plant if they find a nutrient supply. Still, they are exposed to a number of adverse conditions that hamper the conquest of this habitat.

    In contrast to the abundance of organic matter in the soil and the rhizosphere, there are hardly any nutrients on the cuticle of the leaves (phyllosphere). Bacillus and Trichoderma cannot move around actively. Instead, they extend through a growth medium by forming colonies and mycelia. Motionless, void of an energy source, exposed to the dangers of drought and ultraviolet radiation, they can hardly contribute to the protection and fertilization of the plant.

    Exceptions

    There are isolated cases of successful applications of soil-borne microorganisms in the aerial parts of the plant. For example, bees are made to tread on an area soaked with Trichoderma spores when leaving the hive. The bees deposit the spores on strawberry flowers and thereby help to prevent Botrytis after fruit formation. Antagonistic soil microorganisms can also partially protect the root crown which is disproportionally at risk of rot.

    Is it possible to boost the growth of beneficial microorganisms specifically?

    Our free-living microorganisms derive their energy from the breakdown of organic compounds. For this they need a range of supplements that also form part of the growth media used to cultivate microorganisms in Petri dishes. Adding these materials to the soil benefits all species of microorganisms no matter their effect on the plant. So it is not possible to exclusively target the desired microorganisms in this way.

    Still, generally speaking, it is commendable to add compounds that stimulate the growth of soil-borne microorganisms sustainably. An active and ecologically stable soil community bestows a certain resistance on plants against the attack of pathogens. However, one should avoid readily digestible sources of energy, such as sugars that can be broken down easily. Materials which exhibit microscopically small structures that increase their surface area have also turned out as favorable environments for microorganisms to grow.

    New approaches

    Apart from these general considerations, there are new attempts to boost exclusively the growth of beneficial microorganisms. It seems that some polyphenols act as messengers that stimulate the establishment of endomycorrhizal fungi in the root system. Also, the addition of selective growth media on the leaves can boost the development of a desired group of microorganisms on the cuticle. However, at present these new ideas have not yet been established successfully on a commercial scale.

    =

    FAQ

    Microorganisms for the treatment of roots:

    Mycorrhizal fungi, Trichoderma and beneficial bacteria (PGPR)

    This section gives answers to frequent questions about the application, efficacy, compatibility, durability, quality and safety of our microorganisms for the treatment of roots.

    How often should the microorganisms be applied and in which quantities?

    There is a general rule of thumb: Better small amounts often than one big amount once. The aim is to maintain stable populations in the soil that protect the roots over longer periods of time.

    Free living microorganisms, such as rhizobacteria and Trichoderma, frequently establish big populations initially that can collapse again in the course of the growing cycle. In this case the inoculum should be applied several times.

    Reapplying small amounts periodically over extended periods of time also helps to maintain a divers array of beneficial strains. After several species of microorganisms have colonized the root surface successfully, their distribution patterns start to shift. A species that is very dominant at the beginning may fall out completely later. Awkwardly, it may be precisely this species which renders especially valuable services to the crop at a more advanced stage of its development, for example throughout the highly demanding moment of fruit growth.

    The situation is slightly different in microorganisms that are closely associated with the tissue of plant roots, such as mycorrhizal fungi or rhizobia inside root nodules of legumes. Plants that were inoculated well and entirely after germination retain these symbiotic partners until the end of there lives. Reinoculating does generally make less sense.

    Reapplication of EndosporTM

    Positive surprises are not uncommon when reapplying endomycorrhizal fungi. Vineyards and orchards that are several years old often profit from a fresh mycorrhization by EndosporTM. The benign effect of this "refresh" seems to be linked to the competition that occurs between different mycorrhizal species. After the novel application high performing strains replace species that are less efficient in parts of the root system.

    The reapplication should take place at a time of the year when roots tend to grow. In temperate climes this happens in spring. The best moment in tropical and subtropical climes is at the end of the rainy season or - in irrigated crops - at the end of winter

    Should the microorganisms be multiplied before the application?

    Some users propagate the organisms prior to application. Typically, a commercially available spore product undergoes a reproductive process under non-sterile conditions for several days. The aim of this "enrichment" is to generate more infective material for the treatment of plants. Also, once the microorganisms have advanced from spores to colonies or mycelia, they are able to colonize the root surface more immediately.

    We agree that this reproduction can be advantageous at times. Nevertheless, we think that it is not justified in the face of readily available inocula that are technically mature and conveniently priced. Considering the long list of possible disadvantages, we do not recommend to multiply the organisms prior to application.

    The growth medium consists of an energy source (molasses, dextros...), nutrients (N, P...) and other sources of organic material (compost, fibers..). Sometimes these components may not be digested completely by the microorganisms, for example when the fermentation is being interrupted. Applying these components to the plants can have unforeseen consequences.The growth medium consists of an energy source (molasses, dextrose...), nutrients (N, P...) and other sources of organic material (compost, fibers...). Sometimes these components may not be digested completely by the microorganisms, for example when the fermentation is being interrupted. Applying these components to the plants can have unforeseen consequences.

    The additional investment in time and work can only be justified by the substantially improved efficacy of the microorganisms. This criterion is rarely being fulfilled in the context of a modern, economically run plant production.

    Possible disadvantages of multiplying prior to application

    Undigested residues of sugar can serve as a readily available energy source for pathogens that are already present in the crop, such as Xanthomonas or Phytophthora. In contrast to the new-comers, these established organisms are well adapted to the environment and thus able to use the sugar immediately for an explosive growth before they can be suppressed by the beneficial microorganisms. This danger is especially real for leftovers on the leaves after spraying.

    The additional input of nitrates and phosphates can cause imbalances in a highly fine-tuned plant production. Above all care should be taken with hydroponic and semi hydroponic production systems. Their computer controlled, highly optimized nutrient inputs can become imbalanced by the unintended import of an additional nutrient source. There is anecdotal evidence that microorganisms that are multiplied in this way can enter into competition for nutrients with the plants. This cannot happen when applying our high-tech products.

    When crude plant material is used as the source for carbohydrates it can become the avenue for the introduction of pathogens because they are multiplied just as all other microorganisms in the mixture. These materials should be exposed to the high temperatures of a composting process first, in order to kill pathogenic fungi and bacteria. In contrast, the propagation of beneficial rhizobacteria and Trichoderma does not allow for high temperatures.

    This last point leads to the following general consideration: Good commercial inocula consist of blends of pure strains that are produced separately under sterile conditions in the highly controlled environment of industrial bioreactors. This kind of incubation precludes the co-production of undesired microorganisms. All conditions that are important for the growth are strictly controlled, so that the strains do not loose their desired properties. Leftovers of growth media are limited to a minimum. All these factors lead to consistently high quality that is being monitored constantly according to scientifically objective criteria. This is crucial because it is the only way to assure that good results obtained from applications in the field in the first year can be achieved again in the following years.

    The artisanal reproductive process harbors a whole range of uncertainties. The duration of the fermentation and the ambient temperature under which it takes place tend to vary. As a consequence, dramatic changes may occur in the resulting species composition, the remains of the growth medium and the application properties. Since many microorganisms grow together, some species might be suppressed by competition and fall out all together. Mycorrhizal fungi, for once, cannot be reproduced in this way and most likely do not survive this process. The efficacy of the species that do survive may suffer at least partially. Thus, the reproduction process can result in highly variable end products which perform differently when applied to plants. This great number of unknowns has the potential for surprises which can distort planning schedules and time tables and in the worst case cause loss.

    Is there an overdose for the application of microorganisms?

    The fertilization with an overdose of mineral salts can cause the "burning" of the plants. This is not the case for the application of microorganisms. In other words, they either do their job or die. An overdose does not exist in a purely technical sense. Rather, the art of finding the right application rate consists in achieving effects through a sufficient amount of product and within an adequate budget.

    What is the right amount of water for the application of the microorganisms?

    Our products are fine powders or granulates. Some applications require them to be blended into potting mixes or to be mixed with the seeds. Often though they are mixed with water and sprayed or injected through the irrigation system.

    For example, the product BactivaTM is often applied at a rate of 30g per 10L of water. It is important that the spores of the microorganisms are drenched into the root zone. On the other hand, the water absorption capacity of the substrate should not be surpassed, in order to avoid flushing the spores out (for example by dripping through the bottom of irrigation trays).

    From a biological perspective it is not important how much water is being applied, as long as there is enough water around for spore germination. In other words, the main function of the water is to serve as a vehicle. The aim is to introduce the spores as completely as possible into the root zone. The amount of water depends primarily on the application method and the equipment. It should allow for an even distribution of the product in a given production unit (germination tray, pot, raised bed, field or orchard).

    Differences between foliar/soil applications

    The amount of water should be well calibrated when applying biological products, such as Bacillus thuringensis, Beauveria bassiana or Metarhizium anisopliae to the leaves of the plant. The efficacy of these products depends on the degree of surface covered. At the same time, a high concentration of spores is crucial to a good "hit score" when trying to reach all pathogens on the leaves.

    The success of applications in the root system does not depend so much on the concentration of the spores in the immediate proximity of the root and its coverage of the surface. These bacteria and fungi can spread by forming colonies and mycelia. They are saprophytes and can make use of organic matter in the soil to grow towards the pathogens that they control. Conventional wisdom has it that this is virtually impossible for the spores of many microorganisms that live in the nutrient deficient cuticle of the leaves.

    Is it necessary to adjust the pH of the water prior to mixing it with microorganisms?

    All microorganisms thrive at a specific pH range that boosts their growth and efficacy. This is why some suppliers recommend adjusting the pH of the water before introducing the microorganisms. We do not support this view because the microorganisms chosen by us can cope with irrigation water that is somewhat acid or alkaline as long as this pH lies within the limits tolerated by plants. Even if the range is not in the optimum, they do not suffer permanent damage and for this reason there is no need to adjust the pH of the water when mixing.

    Ultimately, it is the pH that the microorganisms encounter in the rhizosphere and the soil that affect their performance. Our strains tolerate more extreme pH-values than the plant. This explains why inoculated plants frequently outperform untreated plants on extremely acid or alkaline soils. The prime example is the successful reforestation of abandoned US mines with the help of the ectomycorrhizal fungus Pisolithus tinctorius after years of futile attempts without the fungus.

    When does it make the most sense to apply microorganisms?

    Applying beneficial microorganisms at regular intervals can improve production success particularly when negative soil properties harm the development of plants and soil organisms. They stimulate the growth of roots that have been damaged by transplant, fight with disease or suffer from soil compaction by boosting the development of the healthy parts while suppressing the pathogens.

    Experience shows that it is uniquely beneficial to introduce microorganisms in soils that have been cultivated with conventional methods. Usually, the plants respond with an improved nutrient uptake, enhanced growth and higher yields.

    Applying microorganisms makes a lot of sense when it is not conceivable that sufficient amounts of beneficial strains and species reach the rhizosphere by natural processes. This is especially true for endomycorrhizal fungi which have spores with large diameters. Normally they are not carried by air and thus absent from germination trays.

    Mycorrhization

    Seedlings that are germinated in peat moss or similar substrates usually cannot form mycorrhizae without the application of mycorrhizal spores. However, treating the plant with the fungus at an early stage gives the fungus the opportunity to invade the whole root area. In the process the fungus undergoes a maturing process just like the plant. Finally, at the moment of transplant, a well developed mycelium supports the plant to overcome the transplant stress. Nonmycorrhizal transplants normally come into contact with mycorrhizal fungi in the field sooner or later. Nevertheless, a late mycorrhization means that they loose out on an important head start at a crucial early moment of the growth cycle.

    There is a huge diversity of crops that benefit from mycorrhization. However, those crops that give high yields over many years, such as vineyards and orchards, are especially attractive. The cost-benefit analysis is unambiguous and they should be treated early on and possibly several times. The investment in Endospor is minute as compared to other costs of crop production and the possible gains. The calculation is different for short lived crops, such as lettuce where the costs of mycorrhization can easily outweigh the benefits. In this case a field trial should give a clearer picture.

    Why do not all growers and agronomists already apply microorganisms?

    The worldwide use of microorganisms in plant production is steadily climbing. Their potential to complement or substitute for chemical fertilizers and plant protection products has been proven scientifically. However, their use of microorganisms is still in its infancy when compared to the predominance of chemicals. The reasons are manifold and sometimes subject to controversial discussions.

    Many suppliers of biological plant protection products argue that users and lawmakers are being influenced by the intense lobbying of the financially powerful chemical industry. Manufacturers of biological alternatives too have increased their lobbying activities over the past few years. However, these outfits are for the most part small, local and service orientated. Their lobbying efforts tend to pale in the face of the ubiquitous presence of multinational chemical companies.

    Small manufacturers of biological products cannot pay for the costly registration processes of plant protection products that are set by the high standards applicable to the chemical industry. At any rate this hold true for the present initial stage with the absence of big and lucrative markets that would justify these investments.

    As a result, suppliers of "soil amendments" or"plant fortifiers" have to limit their claims to vague statements about the mode of action and advertise any aimed for pesticidal effects as "side effects". Once corned into this category, effective products are put together with dubious "snake oils" that do not pass a thorough scientific efficacy test

    "Conservative" users

    The often quoted assertion that many growers and farmers are "conservative" and thus are not easily convinced by new developments does not explain anything. The sector has been shaped by all those technological trends that have transformed other branches of the economy, such as industrial rationalization, computerization and globalization. Neither is there a shortfall of regular crisis moments that spur change, like the increase of energy and fertilizer costs or the ever more limited portfolio of plant protection products due to more stringent legal restrictions and the emergence of pest resistance.

    The buyer cannot rely on commonly accepted standards for this nascent industry when choosing between different microbial products. Even the concentration of the stated ingredients can only be verified by costly analysis. This results in a buyers beware marketplace. By this count some few "lemons" of doubtful quality can harm the reputation of the whole industry, especially if fraudulent suppliers exaggerate claims for a quick buck.

    Over time, the increasing interest and turnover unleashes a growth in high quality products and the consumer's brand awareness. We look with confidence into the future and believe that new technologies that create real value will prevail eventually.

    Is it possible to use soil-borne microorganisms for the control of leaf disease or for foliar fertilization?

    Mycorrhizal fungi cannot grow on leaves. They have to be applied to the roots. This is different for many free living bacteria and fungi of the rhizosphere. Most can grow in the aerial parts of the plant if they find a nutrient supply. Still, they are exposed to a number of adverse conditions that hamper the conquest of this habitat.

    In contrast to the abundance of organic matter in the soil and the rhizosphere, there are hardly any nutrients on the cuticle of the leaves (phyllosphere). Bacillus and Trichoderma cannot move around actively. Instead, they extend through a growth medium by forming colonies and mycelia. Motionless, void of an energy source, exposed to the dangers of drought and ultraviolet radiation, they can hardly contribute to the protection and fertilization of the plant.

    Exceptions

    There are isolated cases of successful applications of soil-borne microorganisms in the aerial parts of the plant. For example, bees are made to tread on an area soaked with Trichoderma spores when leaving the hive. The bees deposit the spores on strawberry flowers and thereby help to prevent Botrytis after fruit formation. Antagonistic soil microorganisms can also partially protect the root crown which is disproportionally at risk of rot.

    Is it possible to boost the growth of beneficial microorganisms specifically?

    Our free-living microorganisms derive their energy from the breakdown of organic compounds. For this they need a range of supplements that also form part of the growth media used to cultivate microorganisms in Petri dishes. Adding these materials to the soil benefits all species of microorganisms no matter their effect on the plant. So it is not possible to exclusively target the desired microorganisms in this way.

    Still, generally speaking, it is commendable to add compounds that stimulate the growth of soil-borne microorganisms sustainably. An active and ecologically stable soil community bestows a certain resistance on plants against the attack of pathogens. However, one should avoid readily digestible sources of energy, such as sugars that can be broken down easily. Materials which exhibit microscopically small structures that increase their surface area have also turned out as favorable environments for microorganisms to grow.

    New approaches

    Apart from these general considerations, there are new attempts to boost exclusively the growth of beneficial microorganisms. It seems that some polyphenols act as messengers that stimulate the establishment of endomycorrhizal fungi in the root system. Also, the addition of selective growth media on the leaves can boost the development of a desired group of microorganisms on the cuticle. However, at present these new ideas have not yet been established successfully on a commercial scale.