Disease Control

Introduction

Dow AgroSciences UK, via Landseer Limited, provide solutions to many of the most commonly occurring fruit diseases. These include apple scab, pear scab, powdery mildew and vine downy mildew.

Biology

Scab Diseases

Apple scab (Venturia inaequalis) and Pear scab (Venturia pirina) fungi are able to overwinter on fallen leaves until new spore cases develop in early spring. During periods of wet weather spores are released, that then germinate on new leaves and fruitlets, causing new scab infections to develop. Infected tissue then produces further spores that continue the spread of the disease. Infected fruit is spotted, distorted and, in the worst cases, unsaleable.

Powdery Mildew

Apple Powdery Mildew (Podosphaera leucotricha)

Infection with powdery mildew can cause severe reduction in both yield and quality of apple crops grown in the UK. Overwintering occurs in buds and when new spring growth emerges from infected tissue it appears white and mealy due to the presence of a large number of spores. Affected leaves and blossom will wither, die and drop from the tree. In many cases where a terminal bud is infected over winter the shoot it produces will appear silver and the leaves will be infected with mildew. Primary outbreaks lead to secondary infection of young leaves, new shoots and growing points.

Pear Powdery Mildew (Podosphaera leucotricha)

The life cycle of powdery mildew on pears is similar to that on apples described above. Infection of pears with powdery mildew occurs sporadically but can be very severe on certain cultivars. Most commonly, symptoms appear as russet on the fruit.

American Gooseberry Mildew (Sphaerotheca mors-uvae)

Blackcurrants, as well as gooseberries, are susceptible to infection with American Gooseberry mildew. Attacked plants suffer premature leaf loss and produce misshapen fruit. White powdery growth occurs on young leaves, shoots and fruits. Symptoms are worst on soft plant growth produced during warm weather. In late summer and early autumn the infection becomes a brown layer on the plant, containing black spore cases which then overwinter. Most varieties of blackcurrant and gooseberry grown in the UK are susceptible to attack from American gooseberry mildew.

Strawberry Mildew (Sphaerotheca macularis)

Protected crops of strawberries are most at risk from infection with Strawberry mildew. In severe cases badly misshapen, shrivelled and unmarketable fruit is produced. Attacks in spring are defined by areas of dark colouring on the upper side of leaves with spores produced on the underside. Affected leaves can sometimes curl, giving the appearance of drought stress. The fungus spreads from infected leaves to new leaves, blossoms and fruit. Strawberry mildew is able to overwinter on leaf tissue.

Vine Downy Mildew (Plasmopara viticola)

This disease is not generally widespread, but can cause severe damage where it does occur. Light green patches appear on the upper surface of infected leaves. These correspond to areas of the sporulating fungus on the underside. Diseased leaf tissue becomes dry and brittle and the fruit is shrivelled. Overwintering spores are produced on infected leaves and these renew the disease cycle in the following spring.

Product Choice

Successful control of diseases attacking fruit crops relies on a well-managed program of appropriate fungicide applications. Dow AgroSciences manufacture a number of fungicide products with recommendations for control of fruit diseases.

Scab Diseases (Venturia inaequalis and Venturia pirina)

Scab diseases of apples and pears can be controlled with Indar* 5EW (active ingredient fenbuconazole) and Systhane* 20EW (myclobutanil).

Learn more about these fungicides by reading the product pages.

Apple Powdery Mildew (Podosphaera leucotricha)

Apple powdery mildew can be treated with Indar 5EW (fenbuconazole) and Systhane 20EW (myclobutanil).

Learn more about these fungicides by reading the product pages.

Pear Powdery Mildew (Podosphaera leucotricha)

Pear powdery mildew can be treated with Indar 5EW (fenbuconazole) and Systhane 20EW (myclobutanil).

Learn more about these fungicides by reading the product pages.

American Gooseberry Mildew (Sphaerotheca mors-uvae)

American Gooseberry mildew can be controlled in blackcurrants and gooseberries using Systhane 20EW (myclobutanil).

Learn more about Systhane 20EW

Strawberry Mildew (Sphaerotheca macularis)

Strawberry mildew can be controlled using Systhane 20EW (myclobutanil).

Learn more about Systhane 20EW

Summary

  • Many different diseases threaten the yield, quality and profitability of fruit crops grown in the UK
  • A fully integrated approach to disease control is necessary to maximise protection
  • Dow AgroSciences produce a number of fungicides that can be used by UK fruit growers
  • Detailed information and full technical support is available from Landseer Limited