Treatment for bacterial blight on pears and apples

July 6, 2022

If the pear leaves start to turn brown, blacken and have a burnt appearance, then it is possible that our trees have been affected by bacterial apple blight.

It is one of the most important bacterial diseases that affects the pear crop, the apple crop and the quince crop every year.

Bacterial blight is caused by the Erwinia bacterium (Erwinia amylovora) and is considered a very destructive disease.

Especially in pear trees, like pear fusiclade, it can dry out a large number of trees in the productive phase in a few months.

Bacterial blight causes significant problems both in professional pear, apple and quince crops, as well as in individual trees that we have in our garden.

So let’s see what are the main symptoms of bacterial burn in pear trees, what conditions favor the development of the disease, and how we can deal with it to limit its damage and save our trees.

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What damage does bacterial blight do to pear trees?

Bacterial blight produces characteristic symptoms of blackening of pear leaves, shoots and flowers that look like they have been through a fire.

The attack of the pear usually begins in the spring from the flowers that take on a green color that gradually blacken and dry up.

Then, during the summer, the infestation spreads to the leaves and shoots of the pear, which wither and dry up. The dry seeds and flowers remain on the trees during autumn and winter.

The infestation can even extend to branches, even to the trunk where ulcers appear all over the trunk.

In wet and hot weather conditions, during the summer period, it can appear on the affected leaves, flowers and branches, characteristic glue in the form of drops of amber or cream color, which is called bacterial exudation.

Bacterial blight can even affect pear fruits. Infected fruits initially show a dry rot covered by the characteristic sticky droplets of bacterial exudation and gradually shrivel remaining on the pear tree.

How is bacterial blight on trees transmitted and spread?

Infection and spread of bacterial blight disease is favored at temperatures of 18-30°C and increased relative humidity especially when rainy wet weather prevails.

The newly formed infections are transferred to the pear blossoms by the rain but also by the pollinating insects, the bees.

Transmission of the disease in uncontaminated areas is mainly by infected propagating material, i.e. young fruiting trees from nurseries infected with the disease.

How is bacterial burn treated?

To deal with bacterial blight on pear, apple and quince trees in an ecological way, a combination of measures will be required which we describe in detail below:

1. We choose resistant pear and apple varieties

The most effective way to protect our crop from bacterial blight is to select and plant resistant pear and apple varieties.

For example, we mention the Krystalli, Kieffer and Moonglow pear varieties as well as the Delicious, Golden Delicious, Starkimson and Starking Delicious apple varieties as relatively resistant to bacterial burn.

Extremely sensitive to bacterial burn are the Kontula pear variety, the Pink Lady apple variety and all quince varieties.

2. We remove affected branches to limit the disease

During the spring and summer, we check the pears every week and remove all the affected shoots and branches together with a healthy part of the shoots 20 cm long.

Pruning tools must be disinfected during work in a bleach solution by mixing 2 spoons in a liter of water.

Also, it is important during the winter season to remove lesions (ulcers) that form on thick branches and the trunk and then smear them with a concentrated solution containing 3.5% bordigalle pulp and 3.5% lime.

We should note that in cases where we have heavily infested pear trees, they should be uprooted and then burned to limit infections.

3. Spray with liquid copper during flowering

Timely spraying with liquid copper during flowering is quite effective in controlling blossom blight as well as the spread of the disease in summer.

We perform three sprays with liquid copper on the pear trees during the flowering period every 5 days avoiding in any case to use copper preparations, Bordeaux paste and copper sulfate which can be toxic to some pear varieties.

How we use copper in plants and crops

And a secret about the bacterial burn of apples

The first attack of bacterial blight on pear trees in the Greek area appeared only in 1984 in the region of Arcadia, while in the spring of 1987 a serious epidemic of bacterial blight was observed in pear, apple and quince nurseries which caused great destruction.

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