Category: Cultivation advice
Date published: April 07, 2021

Phytophthora: symptoms starting to show

Phytophthora: symptoms starting to show

The sun is starting to shine and strawberry crops are moving from the vegetative to the generative development stages. Unfortunately, despite all the care and attention given to the crop over the last few weeks, many growers are starting to see a percentage of plants ‘fall out’ due to Phytophthora and other root disorders.

There are limited, if any, curative options available, so we either accept the losses caused by the weak and dying plants, or look at taking steps to promote plant health, and help the crop get through to harvest. Developing and maintaining an active and resilient root zone, will not cure the disease infection, but experience has shown that we can work to manage the symptoms.

What triggers the ‘fall out’?

Root diseases are opportunists. In many cases, the latent population is waiting for the opportunity to enter the crop. Plants that are already infected, but with symptoms not showing, will quickly collapse once the crop comes under pressure.

When plants are going through this generative transition or have a high fruit load in relation to the root capacity, then any susceptibility is exposed. If the demand for assimilates exceeds the supply, then the crop will naturally push resources to meet the needs of the flowers and fruit. As the plant reduces the investment in the roots, they retract and the diversity of the rhizosphere decreases. This leads to three things happening:

  • The uptake of nutrients and water is affected, leading to further stress and occurrence of disorders. Leaf sap analysis at this time will identify potential disorders
  • The die-back on the roots provides an open door for future infections
  • The crop enters a cycle of assimilate shortage, leading to subsequent ‘fall-out’ and fruit and flower quality issues

Functioning roots

We cannot eliminate root diseases, but what we can do is look to keep an active, functioning root system, which supports any plants with a latent infection, and reduces the opportunity for further disorders.

By focusing on continuous tip development and the ‘white root’ biomass, the plant is able support microbial life and keep nutrient and water uptake at an optimum. Any deficiencies in assimilates are reduced and the crop stays in balance for longer.

Look to apply the root biostimulant Vidi Parva (4-5 L/ha) when there is any concern about root stress or dieback. After two or three applications, growers should be able to see root regeneration within the substrate and improved nutrient balance within the canopy and fruit. When inoculating with beneficial microbes (Trianum or Vitix) to develop the diversity in the substrate, the best results are achieved when the root system is active.

For further information of developing plant resilience in soft fruit crops, pleased contact Koppert UK.

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