Biologicals in the world of asparagus

With over 260,000 hectares in the five continents and given its qualities for fresh or processed consumption, asparagus is a vegetable widely marketed internationally. In its development, the use of biological inputs is increasing, to meet the demands of markets that require innocuousness and respect for the environment, without renouncing in the least to the product quality standard to which they are accustomed.

Francisco Fabres

Organic products are playing an increasingly prominent role in asparagus production, as shown in the most recent edition of Asparagus World magazine, #4 2022, the leading specialized media in this crop.

Numerous articles or segments of reports address these issues. Agrosome's expert consultant Julien Rocherieux wrote in the "What's new in asparagus science" section about asparagus spear decay syndrome (SDS). It is one of the main phytosanitary problems of the crop worldwide, characterized by a gradual loss of vigor that can even lead to plant death. Not only are economic losses severe, but also crop replanting is limited. The complex syndrome involves a set of biotic and abiotic factors, in which Fusarium plays a major role. Fusarium juega un rol principal.

Control of decay with Bacillus and with pellets of Brassica

In Spain, Lopez-Moreno et al. (2021) studied different treatments against SDS to measure their effect on physiological parameters and nutritional quality of turions. Four different treatments were applied in sectors severely affected by the problem:

• Untreated soils (control)
• Biofumigation with pellets of Brassica.
• Biofumigation with chicken manure pellets.
• Disinfection with Dazomet.

The results showed that Brassica pellets and Dazomet treatments were the most effective. Brassica y con Dazomet fueron los más eficaces.

To avoid the use of agrochemicals, the Capote research team (2021) proposes the use of alternative control methods for the three most important Fusarium species in relation to SDS. In vitro antagonism tests revealed that certain bacteria inhibit the growth of mycelia of the three Fusarium. Bacillus paralicheniformis Hvs2 y Bacillus velezensis FC37 were the most effective in controlling F. proliferatum and F. oxysporum f. sp. asparagi. Data suggest that these strains can be used as potential biocontrol agents to provide a sustainable, environmentally friendly strategy in soils with the decay problem.

Smells that trap the asparagus beetle

Guy Dubon, co-editor of Asparagus World, wrote about the asparagus beetle or cryocero of asparagus (Crioceris asparagi), the most serious pest in the aerial part of the crop in countries such as France, Spain and Germany. It is also present in North America. Due to bans on the use of neonicotenoid insecticides, pyrethroids were in many cases left as the only chemical alternative, but their continued use can lead to the development of resistance.

This has led to the search for options, such as the use of insect repellent plant macerations or other alternatives of biological origin. Such is the case of CryoTrap, under development by the Invenio station (Landes, France) in partnership with the company Agriodor. It is a trap based on the use of volatile organic compounds (VOCs) produced by either asparagus or beetles.

"Humans live in a visual world, but other living things, including pests, live in a world of smells”, said Ené Leppik, founder of Agriodor. "Part of our work tries to identify the 'olfactory bouquet' of asparagus, which is 90% composed of the same molecule," specified Romain Warney, specialist from Invenio.

Possibilities currently under study include luring the beetles with VOCs into the traps to reduce their population, as well as the use of pheromone aggregates.

"Humans live in a visual world, but other living things, including pests, live in a world of smells”

Ené Leppik, founder of AgriOdor

Biostimulants and their impact on productivity and quality

Ali Assaf, Francisco de la Torre, Javier Zuzunaga and Dominique Ruggli -from Innovak Global and CIAD (Mexico), and the Polytechnic University of Valencia (Spain)- analyze "Biostimulants and their impact on asparagus productivity and quality". By increasing root exudation, they argue, biostimulants promote colonization of the rhizosphere by native microbiota and consortia of beneficial exogenous microorganisms. The result is an enhancement of the microbial population, an increase in biodiversity, as well as an improvement in nutrient availability and increased root growth.

Exudates play a key role in the interaction of plants with beneficial soil microorganisms.

Given the key role of exudates in the interaction of plants with beneficial soil microorganisms, it is desirable to use biostimulants that promote exudation, the authors propose. Some manufacturers claim that their biostimulants containing aromatic compounds (polyphenols and flavonoids) promote the overexpression of genes linked to root formation (endogenous synthesis of auxins and their transporters) and the active transport of molecules (ATPases), as well as root durability by delaying senescence through the production of antioxidants. All of the above results in an increase in the production of exudates.

Some bacteria (i.e. Bacillus sp.) and fungi (i.e. Penicillium) can provide nutrients such as phosphorus and potassium that are not commonly bioavailable. They do so by producing organic acids or enzymes. Endomycorrhizal fungi are particularly effective in phosphorus mobilization, water uptake, tolerance to biotic and abiotic stresses and promotion of soil structure aggregation. Two management factors can be used for crops to obtain the described benefits: increasing the amount of beneficial fungi and bacteria, and diversifying the composition of microorganism communities. Numerous reports verify that soils with numerous and varied populations of fungi and bacteria induce tolerance to biotic and abiotic stresses. In addition, this abundance of beneficial organisms - including antagonists through antibiosis or parasitism - leaves little space or nutrients for the development of disease-causing agents, thus acting as biological barriers.

Using molecular biology techniques (qPCR and metagenomic analysis), the effect on bacterial populations and their diversity was measured using two biostimulants (microbial and biochemical) applied to a crop of asparagus variety Darlise. Results from two seasons (2019/20 and 2020/21) in Aquitaine, France, proved that both products induced increased exudation and activity, thus ensuring colonization of the rhizosphere by a beneficial consortium containing Bacillus, Azospirillum, Trichoderma and Penicilliumstrains. At the same time, they stimulated the interactions of the native root microbiota. Consequently, an increase in microorganism populations and their biodiversity was detected, which led to a greater availability of nutrients and an increase in root development and activity. A virtuous circle was generated, since as their vigor increased, plants accumulated sufficient reserves to generate good yields, meeting their quality requirements. The biostimulants evaluated, the researchers add in their conclusions, can bring two benefits to farmers:

1. Earlier harvesting to access better market prices.
2. Obtaining larger calibers, of higher commercial value.

Ever more innovations

In the article "Ever more innovations", corresponding to products entering the market, among the innovations presented are several from the bio area:

The soil application of GAIA SOL, 3 kg/ha, sprayed on the soil in February (August in the southern hemisphere), before hilling, in the context of conventional management, optimized yields by enabling the development of extra size turions (+16%), resulting in a better quality and more profitable product, according to Medinbio. GAIA SOL also favored plant condition and reduced the percentage of unmarketable caliber turions by 26%. "The combined action of the synergistic Bacillus and Trichoderma in GAIA SOL led to a higher fraction of superior quality turions and a reduction in yield losses," the company said.

Organic products are providing answers to turions's health and quality.

Terrial launched Forti K+, its new potassium fertilizer (2-0-40 + 45 SO3), derived from the production of bio-based organic acids. The product, certified organic, low in chlorine, will make it possible to develop customized formulations to meet various demands and specifications. Forti K+ will be marketed in compact format (pure or mixed) and encapsulated (mixed with organic matter). Evaluations have shown higher yields and improved nutritional qualities, thanks to efficient sugar synthesis, storage qualities and a consequent increase in shock resistance, handling and better preservation. The product will be available in a few months for gardening, viticulture, fruit growing and crops.

Founded three years ago, the French start-up Zéro Résidu® focuses on phytosanitation, pest control and soil fertility by developing chemical-free solutions. Thus, they have sought active ingredients from different parts of the world (yeasts, bacteria, essential oils, algae, botanical extracts, etc.) to use them in exclusive agronomic formulas that generate an immunizing response of plants against pathogen attacks. All its solutions can be used in organic production.

Experience in compost microbiology and use of organic techniques in England

Lastly, in the section on country reports, Julie Buttler, in "The secrets to an extra early asparagus season in England'', consulted Grzesiek Putyra, technical director of New Forest Furit's about their use of microbiology to obtain better compost. Putyra explains that the firm uses microbiology to convert coconut fiber into the richest possible compost. This aims to have the same spectrum of bacteria (such as the Trichoderma, Mycorrhiza and Bacillusfound in a healthy natural production system. "We have special instruments to measure the bacteria/fungi ratio, which is very important for asparagus, and also carbon, organic matter and microbial biomass," he says. Traditional techniques are used to treat the soil, including the application of earthworms. "While most commercial growers focus on nitrogen, phosphorus and potassium applications to the soil, we use humates and 3 different species of algae in order to deliver to the plants over 70 nutrients found in the ocean," he adds.

Last year they dedicated to reducing the use of fungicides and pesticides, and this season they were reduced to zero, as were nitrogen fertilizers. They only biocontrol and weed by hand. Although the farm is not organic, many organic techniques are applied. Thanks to all these measures, Putyra explains, the plants show no signs of disease, their nutrient uptake is higher, and the turions reach 7-8 Brix, compared to an industry average of 4-6.

The full version of Asparagus World, with articles in different languages, is available at https://www.eurofresh-distribution.com/product/asparagus-world-magazine-4-year-2022/

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