What are Brown Spots on Grapes? The Answer! (2024)

One of the most popular berries worldwide is grapes, a fruit produced by the deciduous woody vines of the Vitis genus.

Grapes have numerous uses; from being served as a tasty morning meal to being extracted for world-class wine, this delicious pome has it all.

However, all these mouth-watering uses come with a price; occasionally, grapes may fall prey to various infections and infestations, and subsequently, turn brown.

What are Brown Spots on Grapes?

Unfortunately, grapes are almost as popular with insects and fungal organisms as they are among humans. Reasons for brown spots on grapes are insect infestation, certain fungal infections, bacterial diseases, and measles. Measles is a disease caused by the measles virus.

Causes for Brown Spots and Their Solutions

Pest Infestation

Not surprisingly, plenty of insects enjoy feasting on grapes. However, insects have a greater liking for the foliage compared to humans preferring the fruits.

The insects that frequently infest grapes include the Grape Leaffolder, vinegar flies, light-brown apple moths, and hoplia beetles.

The pests’ persistent sucking of the nutritious substance causes brown discoloration, accompanied by premature leaf-drop and sometimes brownish-red spots that resemble sunburn.

Some insects, mainly the larvae of the light-brown apple moths, directly enter the fruit and begin sucking on it; this leads to fruit-rotting.

For someone who nurtures and waits for months for this delicious fruit to ripen, seeing brown spots on grapes is nothing less than an utter nightmare.

Fortunately, there are solutions to the problem.

I suggest using insecticides containing carbaryl or spinosad or use horticultural oil to get rid of pests.

Fungal Attack

The fungus Elsinoe ampelina is a common attacker of the home-grown grapes.

It causes Anthracnose of grapes, which is the formation of brown or black spots on the fruit.

The distinctive spots resemble a bird’s eye, hence the alternate name ‘bird’s eye rot.’ The disease mostly occurs in the warm, wet seasons.

It affects all green parts of the plant-vines, leaves, stems, tendrils, and fruit. The most affected fruits are stripped of nutrients and start to look green or purple.

In combination with the lack of fungicide spray, the summer heat significantly increases the fruit’s susceptibility to this fungus.

It paves an easy way for the Ampelina to damage the grapes and cause considerable defoliation.

As a result, the fruit is robbed of its sugar, and the ripening is delayed or improper.

Luckily, Anthracnose is avoidable if good cultural hygiene is maintained along with the periodical use of fungicide spray.

Bacterial Infection

The bacterial diseases are right behind the fungal infections when it comes to grapes.

Pierce’s disease impairs the plant’s water-absorbing ability, leading to severe dehydration primarily during the growing season.

The affected plant develops yellow or red leaves. They become brittle and dry and eventually fall off due to an inadequate water supply.

The green berries turn brown and shrink in size.

Consequently, the new growth is also retarded. An effective way to prevent Pierce’s disease is controlling sharpshooter insects that resemble leafhoppers.

The insects actively carry the disease from one plant to another. I recommend putting sticky traps in and around your vineyard that lower the probability of sharpshooters’ attack.

Furthermore, you can keep your yard free of weeds and promptly remove the affected vines.

Measles

A disease that is nearly eradicated from most modern countries remains an issue in the plant world.

While humans have won against this disease, plants remain in an ongoing war.

Measles, a fungal infection, attacks grapevines through damaged and rotting plant areas.

It causes various symptoms, ranging from discoloration to foliage that seems dried out, sunburnt, and takes on a reddish-yellow appearance.

Eventually, the severely affected leaves fall off, further weakening the plant. The dark brown patches cover the grapes, ruining the taste and the look of the fruit.

Sometimes the malevolent fungus may lead to rotting, or worse, cracking. The cracks allow additional pests to feed on the damaged plant.

Use lime sulfur on the affected vine’s open areas to control the spread.

Other Reasons for Brown Spots on Grapes

Botrytis Blight

Botrytis blight, or summer rot, are similar terms for the same thing. It causes ripening grapes to dry out and rot.

The damaged vines develop lesions, and the formed blossoms drop prematurely.

Initially, the rot appears on a small area; however, it becomes more apparent as the fruit grows, attacking the entire cluster.

It most typically occurs during springtime, when the berries ripen. The insects and other animals feed on it, gradually depleting the fruit of its vitamins.

According to research, removing a few of the upper leaves and lateral shoots of the fully-developed fruit significantly lowers infection probability.

However, please do not remove all the leaves, as they help shade and protect the plant from the sun.

Insufficient Watering

Providing inadequate water to your grape plants can cause a long list of problems; this includes the formation of brown spots.

The grapevines are relatively sensitive to watering.

They require water weekly; failure to do so can lead to discoloration.

General Grape Management

To generally avoid and treat the development of brown spots on grapes, you may do one or all of the following:

Adequate Planting Space

Spacing vines correctly is the key to prevent the spread of infection from one vine to another.

Additionally, opt for a planting site that receives plenty of sunlight and good ventilation.

I also suggest that you keep the vines off the ground and ensure that they are tied properly. The vines above the ground are less likely to get wet and catch infections.

Good Sanitation

Whenever you notice any disease signs, remove the infected vines, leaves, or fruit clusters before the infection spreads to other healthy parts.

I also advise you to place any wild grapes that you have away from your plant as they may harbor the disease.

Furthermore, prevent and immediately eliminate any weed growth, so the humidity remains relatively low—this practice aids in lowering the occurrence of fungal infections.

Read about how to grow Grapes next.

Frequently Asked Questions About Brown Spots on Grapes

Can I eat grapes with brown spots?

In most cases, surprisingly, the grapes with brown spots are just as edible as regular normal grapes. However, if they have a severe infection, it is better to discard them.

How can you tell if grapes are spoiled?

Rotten or sour grapes usually develop a soft texture and have brown discoloration all over. They may also have a smell similar to vinegar and eventually be covered with mold.

Can you get sick from eating old grapes?