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Syngenta’s Switch fungicide controls Botrytis

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article image Switch fungicide controls Botrytis

Syngenta  offer Switch, an active fungicide that controls Botrytis. Switch can be used as botryticide to enhance Botrytis protection.

Botrytis is a weak pathogen in that it rarely attacks healthy plant tissue. Instead botrytis tends to attack dead, injured (e.g., light brown apple moth (LBAM) or wind damaged tissue), highly succulent (soft) growth, or senescent (dying or decaying) tissues such as flower caps and ripening fruit.

Botrytis spores (conidia) require a water film for germination at temperatures between 1° to 30°C (the optimal being 18°C and greater than 90% RH).

Germination of the spores can occur in as little as 1.5 to 2 hours. For the infection, wetness or RH of at least 98 to 100% must persist for at least 16 hours at 20°C.

Susceptibility to infection
There is a long-running debate about when botrytis infection is most likely to occur, and thus, when fungicide sprays are highly beneficial.

The first school of thought is that most botrytis is simply due to the pre-harvest activation of early latent infections (i.e. disease symptoms at harvest are merely the expression of infections that were initiated back during bloom).

Latent infections at flowering are generally the result of wet conditions, a prolonged flowering period, tissue damage (LBAM, wind etc); some, but not most, can develop into berry rot by harvest. The relationship between latent infection levels and disease severity at harvest appears to be inconsistent.

During flowering if these conditions are present over the flowering period (e.g., 80% cap fall) one should apply a botrytis fungicide that offers the maximum possible protection of these latent infections. Switch has proven itself both in Australia and internationally to be the ideal botryticide in the market.

Trials conducted by Syngenta at Myers Flat in Victoria in 1998 showed that one Switch application applied at 80% capfall showed significantly better control of botrytis at harvest than two applications of Scala applied at both 80% capfall and pre-bunch closure.

Application timings:

  • Switch: Applied at 80% capfall only
  • Scala: Applied at 80% capfall and pre-bunch closure
  • Rovral: Applied at 80% capfall and pre-bunch closure and pre-harvest
  • Sumisclex: Applied at 80% capfall and pre-bunch closure

The second school of thought is that early latent infections do indeed account for some, but are not solely responsible for all botrytis infected berries seen at harvest, but that grape berries are actually most susceptible to acquiring infections from veraison onwards.

Late season botrytis infection occurs due to the increasing susceptibility of the berries to botrytis as they begin to soften (veraison), combined with botrytis infected plant material and suitable environmental conditions (e.g. warm, wet and humid) rather than being solely the result of a latent infection at flowering.

However, if conditions are not conducive to the development of botrytis during flowering (dry, little or no damage and the flowering period is short) one should consider using an effective cheaper systemic alternative (e.g. Carbendazim) over the flowering period.

Choosing instead to protect the fruit against the costly late season botrytis infections, by applying a persistent curative and protectant fungicide at the critical pre-bunch closure timing (growth stage E & L 31, berries pea sized (7mm in diameter)).

The critical growth stage
Pre-bunch closure is a critical growth stage for the timing of botrytis sprays as it the latest growth stage at which the user can effectively get a fungicide inside the bunch to protect the developing bunch against or reduce the impact of botrytis infections that may develop as the fruit ripens.

The period to apply a pre-bunch closure spray is around the growth stage E & L 31 when berries are pea sized (7mm diameter). Switch is approved by the AWRI for use up to the growth stage of E & L 31.

Resistance management

  • Switch (Group I and L): Applied at 800g/ha for persistent botrytis control on leaves and bunches. (Maximum 2 sprays). If three or fewer bunch rot sprays are applied in a season use only one spray per season containing a Group I fungicide. If four or more bunch rot sprays are applied use no more than two sprays containing a Group I fungicide. If used at 80% capfall Switch must not be used again at E-L 31, berries pea sized 7 mm.
  • Benzimadazole – (Group A): If three or fewer bunch rot sprays are applied in a season use only one spray per season containing a Group A fungicide. If four or more bunch rot sprays are applied use no more than two sprays containing a Group A fungicide, unless tank mixed with a registered multi-site (Group Y) fungicide. Do not use a Group A product where resistance is known or suspected.
  • Dicarboximide (Group B): If three or fewer bunch rot sprays are applied in a season use only one spray per season containing a Group B fungicide. If four or more bunch rot sprays are applied use no more than two sprays containing a Group B fungicide, unless tank mixed with a registered multisite (Group Y) fungicide.
  • Teldor - (Group J): If three or fewer bunch rot sprays are applied in a season use only one spray per season containing a Group J fungicide. If four or more bunch rot sprays are applied use no more than two sprays containing a Group J fungicide, unless tank mixed with a registered multi-site (Group Y) fungicide. Use only if a systemic botrytis fungicide was used at 5% cap fall, otherwise use a Benzimadazole fungicide.

While all care has been taken in the provision of this spray programme, environmental, seasonal and other conditions can affect the performance of the treatment accordingly.

Syngenta and/or their agents will not be liable in any way whatsoever for the failure of the treatment where seasonal conditions have changed. If chemical are not used in accordance with the label, they will be at the user’s own discretion and risk.

Switch offers the following benefits:

  • Flexibility with application at either 80% capfall or the critical pre-bunch closure timing
  • Good curative and protectant control of botrytis inside and outside the bunch
  • Fludioxonil is the residual component, which stays mainly on the leaf and fruit surface to protect against any further botrytis spore germination
  • Cyprodinil is the systemic partner, which is taken up into the plant tissue and continuously distributes into other plant parts controlling any latent infections, which may have already developed
  • Acts at four different sites of disease development
  • Persistent bunch protection - no matter whether conditions are hot or cold
  • Built in resistance management strategy, 2 different modes of action (GROUP I and GROUP L fungicide groups)

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