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New natural treatments against ‘mealybugs’

These plant protection methods are developed using natural substances in a controlled application against this pest.
Aimplas

Citrus fruit are the flagship of farming in the Valencian Community, although they also have special relevance in other regions such as Andalusia and Murcia. They play an important role in the environment, protecting the soil from water and wind erosion and actively working to mitigate climate change due to their effect as CO2 sinks. Currently, citrus fruit crops, along with persimmons, share some plant protection problems that are complicated to resolve, such as those commonly known as “Mealybugs”.

These are different species of Pseudococcidae that cause direct and indirect damage to the crops, mainly lessening the quality of the fruit. Additionally, they generate an environment that is suitable for other pests to settle in that cause serious damage, leading to the repeated application of pesticides.

The CITRIC-SÀ Project has arisen as a result of this problem, mainly aimed at obtaining plant protection treatments that fight against the different species of “mealybug” in a more sustainable way, using natural substances, maintaining both yield and competitiveness.

The project is funded by the Valencian Innovation Agency (AVI) and it is coordinated by the Cooperative of Llíria, which is carrying out the new application strategy. It also involves the participation of Idai Nature, a company that is specialised in the design and development of natural products based on botanical extracts; and the Instituto Agroforestal Mediterráneo from the Universitat Politècnica de València (UPV), which is in charge of evaluating the effectiveness of the control of the pseudoccidae on the crops. AIMPLAS is bringing its experience in encapsulation by adsorption and coating of the natural botanical extracts, as well as their incorporation in polymeric matrices.

For this purpose, during the first phases of the project, after the selection of the natural extracts with a potential biocide effect against mealybugs, different innovative methodologies have been designed, optimised and applied, paving the way to the obtaining of 3 differentiated products and treatments. These three treatments are the main centre point of one of the project’s innovations, as the application of the products will be carried out in a localised way and according to the seasonality of the pest, with sustained release functionalised microcapsules for their application in the soil; functionalised whitewash paints, applied onto the trunks with the natural extracts coated for greater persistence and finally, natural substances developed for their application on the leaves using spraying techniques.

Following the first optimisations, the efficiency of the 3 products obtained has been tested in laboratories, where direct contact trials have been carried out giving highly promising effectiveness values.

In the case of the microcapsules, the natural extracts have been coated with a polymeric membrane using a natural, biodegradable polymer, providing a sustained release. This product has shown an initial effectiveness of up to 95%, remaining above 70% for 3 weeks and up to 45% effectiveness 43 days after its application.

The functionalised whitewash paint has been formulated coating the natural extracts using an adsorption process and subsequent incorporation to the paint, achieving an initial effectiveness of 100% and values of around 50% effectiveness after two weeks.

With regard to the development for leaf application, the one showing the best characteristics has shown an initial effectiveness of above 97%.

Based on these results, the 3 products have been optimised and graded for field trials.

Currently, these trials on citrus and persimmon crops are in the development phase where, in addition to evaluating the effectiveness in real conditions, a protocol for use is being developed that allows an exhaustive control and evaluation system of the pest, treating different points:

  • Controlled and localised application of the plant protection products, according to the location of the pest in its life cycle using a holistic control with the 3 products developed.
  • A comparative study of the applicability and functionality of the bio control products obtained on the experimental plots of citrus and persimmon trees.
  • A study of the reduction of the use of conventional plant protection products.

After the first applicability trials, the microcapsules, bio paints and developments for leaf application have been satisfactorily applied using already existing conventional equipment.

In turn, the toxicological and eco-toxicological profile of the products developed for leaf application using standard methods of in vitro trials defined within the current regulation framework are being evaluated. These results, along with the new protocol of use and the effectiveness of the new products, will be available over the next few months.

Alberto González, Researcher in Agriculture and Aquatic Environment at AIMPLAS.

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