If Lupine leaves are turning brown and dying then it is due to root rot. Fungal diseases like Powdery mildew and Downy mildew can kill Lupins too. A serious infestation of aphids/whiteflies can cause great damage to Lupins too.
Lupins are a favorite of cottage gardeners. Lupine plants are nitrogen fixers and are beneficial to your garden in many ways.
Lupin leaves turning brown?
Lupine plant leaves turn brown when the plant is overwatered and is infected by root rot. Brown spots are seen on Lupine leaves when the plant is infected by Brown spot disease. Anthracnose is a disease that turns the leaves brown.
Root rot & Brown leaf spot disease
Overwatering is the main reason why roots get rotten in Lupins. Root rot and brown leaf spot diseases are caused by a fungus called Pleiochaeta setosa.
Overwatering creates waterlogged conditions around your Lupins. Waterlogged conditions favor the growth of root rot-causing fungus.
The fungal infection can be first seen on the leaves of Lupins. Brown spots are formed on the leaves, stems and pods.
These brown spots enlarge with time and form a network of dark spots. In case of a severe infection infected leaves fall off.
Severely infected seed pods transfer the disease to the seeds. Other type of root rot fungi may cause brown spots at the base of the stem.
Brown leaf spot/Root rot control in Lupins
- Rotating the crops is quite beneficial in controlling these diseases in Lupins.
- Avoid splashing water onto the foliage.
- Apply Procymidone or Iprodione based seed-dressing fungicides to reduce the risk of transferring the disease to seeds.
- Get disease-resistant cultivars if possible.
Anthracnose is a fungal disease which can prove fatal to the plant if left untreated. Anthracnose spreads to healthy plants via water splashes.
A number of brown lesions form on the leaves and petioles of Lupins. If a lot of brown lesions form on the petiole, it droops.
Control Anthracnose in Lupins
- Using disease-resistant cultivars is the ideal way to prevent Anthracnose.
- Do not wet the leaves of your Lupins when watering the plants.
- Cut off the infected leaves with pruning shears to prevent a large-scale infection. Spray the infected plant with copper-based fungicide for the best results.
Lupin leaves curling
Lupin leaves curl mainly due to aphid infestation. Whiteflies infestation also curls the leaves of Lupine plants.
Aphid infestation in Lupins
Three types of aphids infest Lupine plants. Cowpea aphids(black), Greenpeach aphid(waxy green) and the Bluegreen aphids.
Aphids are carried to the host plants by ants, so try to control ants around susceptible plants. All three types of aphids cause the same damage to your Lupins.
Aphids cling to the stems and leaves of Lupins and suck out the plant sap. They excrete honeydew which attracts a wide variety of fungi.
Aphid infestation distorts the stems and leaves of Lupins. A severe aphid infestation causes loss of produce. In addition to this aphids transmit a variety of viruses.
Control Aphids in Lupins
- Hang yellow, sticky cards around plants to identify an infestation early.
- Spray off the aphids with a garden hose as soon as you identify them.
- Spray neem oil weekly once until you get rid of aphids completely.
- Get an aphicide that doesn’t kill beneficial insects and only gets rid of pesky aphids. Do this only in the case of a severe aphid infestation.
Whiteflies infestation in Lupins
Whitefly infestation also causes leaf curling in Lupins. You’ll find whiteflies on the undersides of Lupine leaves.
Whiteflies can’t be controlled easily so you better treat them as soon as you see them. Wash them off using a water spray from garden hose.
Whiteflies feed on Lupins and excrete a sticky material called Honeydew. Honeydew attracts a variety of fungi.
Control Whiteflies in Lupins
- Hang yellow, sticky cards around your Lupins to identify their presence earlier.
- Cut off the infested leaves to control their spread.
- Spray Safer’s Insecticidal soap if the whitefly infestation is severe. Spray it once a week for two or three weeks for the best results.
Lupin leaves turning red
Lupin leaves turn red if you feed the plant with a lot of manure. Lupins don’t like to be fed too much manure. If they get a lot of nutrients the chlorophyll in leaves is replaced by red pigment.
If there’s a lot of manure around your Lupine plant get rid of it. Replace the enriched soil with poorer soil. If the plant has been planted recently move it to a different place.
Cut off the leaves that are turning red/yellow with a pair of sterilizer pruning shears. The plants should come back fine.
Why are my Lupin seedlings going yellow?
Lupin seedlings turn yellow due to Chlorosis. Chlorosis in such cases is caused by Iron deficiency. Too much or too little water can turn leaves yellow too.
Iron Chlorosis in Lupins
Lupins turn yellow when the plant can’t absorb adequate amount of Iron from the soil. This can happen due to various reasons like, pH imbalance or poor soil.
Identify Iron chlorosis early and try to treat it before your Lupins die. Iron chlorosis causes abscesses in the leaves of Lupins.
- A good cultural control method is to lower the Phosphorous in the soil. Use fertilizer with lower Phosphorous content.
- You can fix Iron chlorosis in Lupins by using High-Yield Iron Plus Soil Acidifier.
We already discussed what overwatering can do to Lupins. Yellowing of the foliage is the primary sign of root rot in Lupins.
Check the soil with your fingers and water the Lupins only when necessary. Get a soil moisture meter if needed. Make sure the soil drains excess water well.
Underwatering can turn leaves yellow too. Underwatered plant’s leaves turn yellow and dry unlike overwatered plants whose leaves turn yellow but droopy.
Water your Lupins if the soil is dry up to two inches. Check the soil with fingers if you want but do not let the soil go bone dry.
Why do Lupins get Mildew?
Lupins get mildew when they are infected fungi. There are two types of mildew diseases that can affect Lupine plants.
Powdery mildew in Lupins
A powdery layer forms on the Lupine leaves. This powdery layer is usually white/gray color. Small black dots are seen later on the infected leaves.
Cut off the infected Lupine leaves with a pair of pruning shears. Dispose of the infected leaves carefully, do not leave them in the garden.
Downy mildew spreads via water splashes so avoid wetting the leaves when you water your Lupins. Respond as soon as you see the symptoms to revive your plant.
How do you treat Powdery Mildew on lupins?
- Spray a mixture of milk and water(1:9) on the affected leaves on a warm day.
- Mix a tablespoon of baking soda in 8 pints of water. Spray this on the affected leaves.
Downy Mildew in Lupins
Downy mildew is a type of fungal disease whose symptoms are first seen on the undersides of Lupine leaves. Downy mildew is usually seen in spring.
Infected leaves of Lupins turn purple and curl down. A whitish or grayish outgrowth can be seen on the undersides of the leaves.
Just like powdery mildew, downy mildew spreads via water splashes too. So avoid watering the plant from top-down.
Tip: Choose resistant varieties if possible.
Treat Downy mildew in Lupins
- Prune the infected Lupine plant to improve air circulation.
- If you see this disease every year, spray copper fungicide on the plant two/three weeks before the wet season.
- Mix 3/4 tsp. ‘Organocide by Plant Doctor’ in a gallon of water. Spray this on the infected plant to get rid of this disease.
What insects eat Lupin leaves?
Snugs and snails love to munch on Lupine leaves. Slugs and snails not only devour leaves, they also munch on flowerheads.
Some species of slugs can be very destructive. Do not let the slug infestation go out of control as they can damage the produce to a great extent.
Get rid of snails in Lupins
- Crush two garlic bulbs and add them to two pints of water. Take these into a pan and boil for 20 minutes, let it cool.
- To make the spray mix 2 teaspoons of this solution in a gallon of water.
- Spray the plant and the surrounding soil once a week to deter slugs and snails. Do not spray this solution on the blossoms.
Why are my Lupins not flowering?
Lupins fail to flower if they don’t get adequate sunlight. Sunlight is the reason if Lupins look healthy but do not blossom.
Lupins love full-sunlight or partial-shade conditions. Remember that Lupins bloom from late spring to early summer.
I’d advise you to plant your Lupins so that it gets partial sun. Cut off the neighboring plants to allow some sunlight in.
This usually happens in the early summer so keep an eye on your Lupins during this season. Cut your Lupins back after flowering to induce a second round of blossoms.
Do Lupins die back in summer?
Yes, Lupins die back in summer just after the blossom season. Flowers die from the bottom to towards the tip.
Cut back your Lupins hard when you see that the 2/3rds of the flowers are spent/brown. Doing this you can ensure a good blossom the next season.
Deadheading your Lupins is a great way to maintain plant’s resources. A second season of flowering can be seen later in the summer if you’re lucky.
Happy Gardening 🙂