Monilinia fructigena facts for kids

Monilinia fructigena is a tiny fungus that causes a disease called brown rot. It makes fruits like apples, pears, plums, peaches, and cherries rot and go bad.

What is Monilinia fructigena?

There are three main types of Monilinia fungi that cause brown rot in fruits. These are Monilinia laxa, Monilinia fructicola, and Monilinia fructigena.

Monilinia fructigena is the most common cause of brown rot in fruits from the Pome family (like apples and pears) and the Rosaceae family (which includes many fruit trees). Scientists sometimes divide the Monilinia group into two sections based on how they look and how they infect plants. M. fructigena belongs to a group called Junctoriae.

It can be tricky to tell the three Monilinia species apart in a lab. However, scientists have found ways to identify them. For example, by changing how much light they get, they can tell Monilinia fructigena and Monilinia fructicola apart from Monilinia laxa. Also, M. fructigena grows slower than M. fructicola in a lab dish.

The spores of Monilinia fructigena are dry. They don't shoot out but are carried away by the wind. This helps them spread easily from one infected fruit to another, especially when fruits are still on the tree. This fungus can infect fruits at any stage, from tiny young fruitlets to fully grown, ripe fruits.

How Brown Rot Affects Fruits

When Monilinia fructigena infects a fruit, especially early on, you might not see any signs at first. The fruit can look normal as it grows. But as the fruit ripens, small brown spots appear. These spots quickly grow and cause the fruit flesh to rot.

If there's a lot of moisture in the air, fuzzy patches of fungus (called conidial tufts) will grow on the rotten areas. If the air is dry, the fruit might just dry out instead of getting fuzzy.

Brown rot is a big problem for apple trees. The fungus can sometimes spread from the fruit to the branches, causing cankers (damaged areas on the bark). In apples, the rot can sometimes turn from brown to a very dark black color. This is often called "black apple." The skin stays shiny, and the fruit doesn't shrink much until later, when it might rot quickly if stored.

While common on apples, pears, and plums, brown rot from M. fructigena is less often found on peaches, nectarines, or apricots.

The Life Cycle of Brown Rot

Once a fruit is infected, it can rot completely in just a few days. The rotten fruit will be covered in fuzzy fungal growth or tiny fungal threads. If the air is dry, these fuzzy patches might not form.

When infected fruits fall to the ground, the fungus stays alive through winter inside the dried-up, "mummified" fruit. In spring, the fungus grows cup-shaped structures called apothecia. These release tiny spores called ascospores into the wind. These spores then land on new plants and start new infections.

If fallen infected fruits stay moist enough, they can also produce more spores (conidia) that can spread the disease further. Sometimes, the fungus forms a hard, round ball called a sclerotium inside the fruit's core.

Wind is a major way that the spores of Monilinia fructigena spread to new fruits and trees. Rain can also wash spores around, helping them get to places where they can grow.

Insects like wasps, beetles, flies, and butterflies can also carry the fungus from one fruit to another. Birds can also cause small wounds on fruits or trees, which gives the fungus an easy way to get inside and start an infection.

Protecting Fruits from Brown Rot

Controlling brown rot involves several methods. One study showed that using a mix of different pest control methods, including some chemical treatments, led to much lower infection rates compared to using only organic methods.

It's important to know that Monilinia fructigena often enters fruits through wounds. So, controlling insects that might wound the fruit can help prevent the fungus from getting in.

Certain fungicides, like pyraclostrobin and boscalid, can be sprayed on trees after they bloom in spring. These sprays help protect against the first infections.

The spores of Monilinia fructigena are spread by wind, especially when it's warm and dry. Raindrops can also spread the spores. When rain spreads spores, the water also helps the spores grow and start new infections.

Photographs

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  Brown rot on an apple.

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  Close-up of brown rot on a fruit.

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  Another view of brown rot on an apple.