Mint is a perennial plant. Normally, it is quite easy to cultivate. The plants can be grown outdoors, but also in pots on the balcony or terrace. Although mint is hardy and robust, it can sometimes be attacked by pests and diseases. The velvety green leaves of the mint are then very often covered with brown spots and dots. Two diseases are usually responsible for this.
Mint: Brown spots
Brown spots and spots can affect mint leaves and petioles throughout the growing season. It is important to recognize these in good time in order to treat the plants as quickly as possible. The longer nothing is done, the more likely it is that the growths will sooner or later die. You can also infect other plants. Can cause this disease
- mint rust and
- be leaf spot disease.
Mint Rust & Leaf Spot Disease
This disease is caused by rust fungi, an order of the pillar fungi. The spores of these fungi, more precisely of Puccinia menthae, can affect the plants throughout the growing season. A warm, humid climate in particular drastically increases the risk of infection.
notice: The spores of the fungi live as parasites. They do not kill the plant tissue.
During the summer months, it is therefore advisable to regularly examine the mint plants for changes. This is the only way to act quickly if an infection with mint rust has occurred. If small brown spots appear around the site of infection, the mint rust can quickly spread over the entire plant. The first symptoms can appear as early as April. These include
- initially chlorotic (light green to yellow) spots and dots on upper leaf surface
- are bordered by leaf veins
- orange-red to cinnamon-brown fruit bodies with spores on the underside of the leaves in summer
- after bursting, reddish-yellow bumps on the upper side of the leaf around the site of infection
- in autumn there are also dark brown to black cushion-like pustules on the underside of the leaves
- severely infected leaves dry up and fall off
- whole shoots wither
- in addition, petioles and stalks can also be affected
- Plants are infested from the bottom up
- older leaves are infected first
notice: Infected plants lose their typical mint aroma. Compared to healthy plants, these contain up to 60 percent less essential oils.
Similar symptoms occur with leaf spot disease. This is very difficult to distinguish from the mint rust. Both cause damage to the same extent, so there is no difference in how you fight them.
measures
Once this and also the leaf spot disease has broken out, no chemical agents or even household remedies will help to combat it. Further spread can only be curbed by a radical pruning. the procedure is as follows:
- Cut back all shoots close to the ground
- just leave a sleeping eye
- Mint sprouts there again healthy
- Cut back into household waste or burn
- not on the compost heap, risk of spreading
- additionally water the bed with field horsetail broth
- Repeat process
- this brew strengthens new shoots and protects against rust fungus formation
notice: Mint rust affects not only plants from the mint family, but also plants from other plant families such as chamomile marigold and monards.
field horsetail broth
Regular doses of this brew can increase the plants' resistance to fungal diseases. The high proportion of silicic acid, but also potassium and saponins, strengthens the tissue of the plants. The leaf surface becomes more resistant and fungal diseases cannot spread so easily.
Horsetail, also known as horsetail, grows wild in damp places such as embankments, ditches and meadow edges. Alternatively, other species such as swamp horsetail, pond horsetail or meadow horsetail can also be used.
Making a broth from field horsetail is relatively easy:
- Chop up 1 to 1.5 kg of fresh field horsetail with sharp pruning shears
- alternatively 150 to 200 g of dried horsetail can be used
- Soak the clippings in 10 liters of water in a large saucepan
- Soaking time at least 24 hours
- preferably use of rainwater
- then bring everything to a boil
- Simmer at low temperature for 30 minutes
- Strain the broth with a fine-mesh sieve
- let cool down
- Application with watering can or pressure sprayer possible
- If using a syringe, filter decoction again through a cotton diaper or light cotton cloth
- because plant debris can clog the nozzle
- Dilute broth in a 1:5 ratio with water
After the first application of horsetail broth, the process should be repeated every two to three weeks. Not only the plants, but also the soil around the plants should be treated. This promotes resilience and at the same time the plants are supplied with valuable nutrients.
tip: The brew should always be applied in the morning when the weather is sunny. Because the warming rays of the sun intensify the effect of the broth.
Prevent brown mint
Before brown spots and spots on mint leaves have to be combated, some measures should be taken in advance to prevent these diseases. It doesn't even require that much effort.
- Use of healthy or resistant cultivars or species with hairy leaves
- “Multimentha” is recommended
- Constantly loosen the soil around the plants
- pull weeds regularly
- Water plants from below
- wet leaves increase the risk of infection
- always water in the morning
- Water regularly, especially during longer periods of drought and in summer
- Avoid waterlogging
- when planting in tubs, introduce drainage
- further planting distance
- to other plants at least 30 cm
- Observe crop rotation, annual crop rotation in the bed advisable
- loves light sun to half-shade outdoors or on the balcony and terrace
- shady places and too small a distance to other plants promote the formation of rust fungi
- looking for airy space
- Avoid blazing sun and heat, especially around midday
- balanced fertilization in the summer months
- Use of organic fertilizers such as nettle manure or horn shavings
- regularly cut back heavily in autumn
- transplant or repot if necessary
- timely harvesting prevents the formation of rust fungi
tip: If brown to black spots appear together with aphids and ants, then sooty mold fungi can quickly develop. Lice and ants transmit this disease. Action must then be taken quickly. An immediate radical pruning must take place.
Despite all preventive measures, regular inspection of the mint for brown spots and spots is necessary. the diseased plants must be pruned back at the first sign.