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The global search for plant protection solutions that are both
environmentally safe and effective is driven by the need to supply
food to the ever-growing world population. Among the latest
solutions, essential oils are considered to be attractive for plant
protection, for which increasing novel hybrid products and active
ingredients are available.
Tea tree oil (TTO) is a valuable essential oil extracted by
steam distillation of Melaleuca alternifolia (belonging to
family Myrtaceae) leaves. It contains many components of terpenes,
sesquiterpenes, and their respective alcohol. The oil has been
shown to be an effective antiseptic, antifungal and
bactericide.
Over the past decade it was found to be effective against a
broad range of plant-pathogenic fungi in numerous crops, including
vegetables, herbs, coffee, rice, grapevines, bananas, and fruit
trees. New effective alternatives that can provide different and
multiple modes of action with a lower risk for fungicide
resistance, and which place a smaller chemical load on the
environment concomitantly with consistent disease control, are
required to increase options for the control of plant diseases.
The newly developed fungicide Regev EC from Israel's STK Bio-Ag
Technologies, a hybrid formulation containing 200 g/L of the
systemic triazole fungicide difenoconazole plus 400 g/L of TTO, is
a <span/>prepacked
formulation which provides various mechanisms of action against
broad-spectrum of plant pathogens and improved efficacy.
The suggested hybrid solution can be the 'bridge' between
conventional agrochemical farming and sustainable farming. This is
because it is a 'pre-mix', so it is easy-to-use, in the exact same
way as the grower's current chemical pesticide.
Modes of action
The fungicidal and antimicrobial activities of TTO against
fungal pathogens, as documented in the literature, are derived from
its ability to inhibit respiration and disrupt the permeability
barrier presented by the membrane structures of living
organisms.
Recent studies showed that TTO had a moderate effect against
spore germination and significantly inhibited lesion development
and sporulation of fungal pathogen. STK's Timorex Gold TTO was
found to disrupt the fungal cell membrane and cell wall in plant
tissue infected with pathogenic fungi, which explains why it
exhibited strong curative activity against fungal pathogens, making
it a unique product and enabling growers to use it even when the
disease is already visible on the tissue.
In addition, Timorex Gold's TTO was found to be an activator of
plant itself defense mechanisms and systemically induced resistance
in plants.
The sterol biosynthesis inhibitors, including difenoconazole,
affect the fungal cell membrane by inhibiting C-14 demethylation of
lanosterol or 24-methylenedihydrolanosterol, a biosynthesis step
that occurs during conversion of lanosterol to ergosterol, the
final product of fungal cell membrane sterol synthesis. The
different modes of action of TTO and difenoconazole, i.e. a
combination of a natural product with broad-spectrum activity (TTO)
and a traditional site-specific chemical, makes Regev an effective
and unique tool for resistance management which is suitable for
Integrated Pest Management (IPM) programs. This combination results
in a reduced synthetic chemical load on the environment compared to
other mixtures based on two traditional chemicals.
Field trials
Regev is currently used for controlling a broad range of
diseases on arable crops, cereals, fruits crops and vegetables.
Diseases effectively controlled by Regev include powdery mildews,
<span/>apple scab
(Venturia inaequalis), Black Sigatoka (<span/>Mycosphaerella
fijiensis) in banana, species of Alternaria, Cercospora,
Botrytis, Rhizoctonia, Pyricularia, Helminthosporium,
Sclerotium and more. Numerous trials have been conducted with
various crops in different countries. Here we present an example of
Regev activity against black Sigatoka (Mycosphaerella
fijiensis) in banana.
In field trials in Colombia, efficacy of Regev applied alone was
compared to systemic fungicides, each applied in tank mixture with
a protectant fungicide mancozeb. Untreated banana plants served as
controls. Four foliar sprays of each fungicide/mixture were applied
at spray volume of 19 L /ha at 10 days intervals.
Resistance management
Regev has multiple functional activity and presents a lower
probability for resistance development or cross-resistance in plant
pathogens, so it could be an important tool in preventing
development of cross-resistance during the season. Its application
can be rotated with products that exhibit differing modes of action
and to which populations of fungal pathogens have shown a loss of
sensitivity, so that population of pathogens less sensitive to
chemical products can be reduced.
Registration
Regev is already registered in Israel, Philippines, Serbia,
United States and various Latin American countries for various
crops and diseases. It is currently in the process of registration
in Brazil, Mexico and the EU.
Figure 1. Efficacy of Regev (TT+Difenoconazole)
applied alone and systemic plus mancozeb in controlling of black
Sigatoka in banana plantations. Star on bar indicates significant
difference (P < 0.05)
Figure 2. Efficacy of Regev (TT+Difenoconazole)
applied alone and systemic fungicides each plus mancozeb in
controlling of black Sigatoka in banana plantations.
Posted 04 November 2021 by Alan Bullion, Director of Special Reports & Projects, Agribusiness, Energy & Natural Resources
