Biorationals are registered plant protection products generally derived from the natural environment, offering improved benefits for plants, people, and the planet, which are increasingly important factors for Integrated Crop Production to satisfy requirements of the value chain and consumers.
Developments in Biorational products have been progressing rapidly in recent years and indeed, in some crops, such products are now key to modern production methods. It is true, however, that the ornamentals sector has always lagged somewhat behind the vegetable sector in terms of the use of Biorationals.
One of the main reasons for less easy acceptance and penetration of Biorational use in ornamentals is the fact that these crops are sold as whole plants or flowers, including leaves, which must look perfect to be acceptable in the market.
If the pest or disease is not controlled quickly and thoroughly enough, then some crop damage will occur from the pest or disease, and then the price of the ornamental plant or flower will fall to close to zero. Biorational products are often not as strong and long-lasting as conventional products, and so do not give 100% control of all insects or fungi. This means there is a higher commercial risk in using such less strong Biorational products in the many varieties grown by an ornamental grower, which has clearly limited the growth of Biorational usage in the sector. This limitation does not apply in the same way for food crops.
Last but not least, most Biorationals are contact-based products so, to be effective, need to be sprayed to both sides of all leaves. It is very difficult to achieve this in practice, for example in pot plants.
Myzus persicae killed by Azatin (azadirachtine)
If usage is to be increased, the Biorational products need to be crop safe, fast-acting, and perform for at least six or seven days. Of course, if this could be guaranteed, levels of uptake would undoubtedly be much higher. Systemic or at least translaminar bio-active ingredients would be ideal, but they are almost non-existent.
In the current situation, it seems that the use of Biorationals in ornamentals is highest in the central zone countries, especially in greenhouses, where the climate is being controlled, and beneficial insects are also quite often used successfully. Biorational products tend to be more compatible with beneficials and thus more used in Integrated Pest Management (IPM) crop programs. In fruiting vegetables, it is normal to create a balance between the pest and beneficials, and Biorationals offer a perfect means to correct that balance if necessary. In ornamentals it is more difficult to create the balance and growers have a zero-tolerance of any pest damage by the time they get to harvest - they cannot risk such damage. In principle, every grower is willing to use and/or test Biorationals, but again the product must be crop safe under all conditions and performing well.
Aulacorthum solani killed by Eradicoat Max (maltodextrine)
In recent years it has become more difficult to protect crops from aphids due to the loss of registrations of chemical products and therefore the demand for more effective Biorationals as alternatives is growing. Certis is a leading player in developing Biorationals and recent findings from some of its work on aphid control illustrate the complexity of the challenge to meet all the necessary criteria for successful solutions that will be acceptable to ornamentals growers.
Trials at Certis' Innovation Center in Naaldwijk, The Netherlands
New Biorational products and some insecticides already registered against whitefly and thrips were tested on aphids. The trials were started on a small scale and the first screening was to check if the products showed efficacy given optimal application and under ideal conditions. A leaf disc was placed on agar in a small, vented plastic box with aphid nymphs or adults. The aphids were sprayed with different screening products and different dose rates. After two days and seven days the aphids were counted (live and dead).
Leaf disc on agar in a small, vented, plastic box with aphid nymphs
Some products showed very good efficacy on aphids, even with low dose rates, others showed a clear dose-rate effect, and some showed hardly any efficacy at all. There were also differences between levels of efficacy on nymphae and on adult aphids. The results also showed something about the mode of action of the products.
Physical acting insecticides like fatty acids (Neudosan) or maltodextrine (Eradicoat Max) based products showed quick efficacy: within a few hours of spraying the aphids were dead. When the spray coverage of the insect was sub-optimal, the aphids were not killed and were able to walk away. Entomopathogenic fungi, like Beauveria bassiana (BotaniGard) and azadirachtin (Azatin) are more slow-acting products that showed poor results after two days, but much better efficacy after a week.
Azadirachtin was more effective on nymph stages than on adults and fewer offspring were observed. Azadirachtin is an Insect Growth Regulator (IGR), so these results are not a surprise and can be explained by the mode of action, which prevents the next larvae stage/development stage of the young aphids. Its other mode of action is a repellent effect, and this was more difficult to see in these petri dish trials, but was clearly seen in practice after more crop applications.
After this screening, the products will be tested on plants in a more practical setting. The search for satisfactory solutions continues, including not only the Biorational products themselves, but also the techniques used to apply them and the conditions pertaining to ornamental production.
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