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Passion flowers require relatively little care and maintenance to grow successfully. Once established, they can grow well, left virtually untouched for years. In fact, they are generally problem free with nothing more than a few aphids to worry about most of the time.
However, there are a few passion flower pests and diseases that can take a liking to your passion flowers which might make an appearance, as I have found out a few times over the years. With this in mind, it’s good to be on the lookout and know what to do to tackle them before they get out of control. I also have a guide on passion flower problems that includes some issues not related to pests or diseases.
Passion flower pests
Aphids (Greenfly, blackfly, whitefly)
Aphids are probably the most common and you most certainly seen them before and are no stranger to them. The most common are greenfly, blackfly and whitefly for passion flowers grown inside greenhouses. These insects suck the sap out of the leaves of your plant, leaving them deformed. This reduces the strength of the plant and makes it weak.
You may notice the presence of aphids by the sticky substance called honeydew they leave behind. Ants in particular love honeydew, so you may have an infestation of these insects as well. Plus black sooty mould grows in the honeydew so you may also notice this.
What to do
Aphids are the food of many other garden pests and insects in your garden, including ladybirds bugs and birds. So they can be part of a balanced garden ecosystem. However, if they become an infestation, you can squish their colonies between your thumb and fingers for a non-pesticide control method. Not nice by effective on smaller infestations. Encourage the insects that eat aphids into your garden, such as ladybirds/ladybugs and ground beetles. You can even buy ladybirds off Amazon.
I usually use a general garden pesticide in bad aphid investigations. You can also use organic sprays such as natural pyrethrum or plant oils which can also be effective. You need to reapply these solutions often as they have a short working life. what I like about pesticides is they are taken in by the plant and can last for several months.
Glasshouse red spider mites
These red spider mites appear on passion flowers that are in the greenhouse and also on those in the ground outside. The spider mites love to suck the sap from the leaves, which leads to the early loss of leaves on the plant. You notice them by ravaged and mottled foliage and by leaves dropping when they shouldn’t. You may also see a fine spider webbing throughout the plant.
The spider mites are active during summer in hot and dry conditions. And at their most extreme can kill your passion flower plant.
What to do
Keeping the environment around the plants at a higher humidity discourages these mites that like dryness which is why they are more of a problem with passion flowers grown in greenhouses.
Remove severely infested plants before the fall when the female spider mites look for somewhere to overwinter. In the garden, clean out old stems, debris and other plant matter before the winter so as to not give the spider mites homes for the colder months.
If you must resort to pesticides, consider organic sprays such as natural pyrethrum and plant oils. You need to reapply these sprays frequently as they don’t last very long.
If your passion flowers are in a greenhouse, consider using a greenhouse fumigant. Seal the greenhouse and follow the instructions on the product very carefully.
The glasshouse whitefly, as briefly mentioned under aphids, is similar to red spider mites in its destructive capabilities for your passion flower. It sucks the sap of the plant’s leaves, leaving them mottled and weak. The honeydew substance it leaves behind is a breeding ground for black sooty mould and attracts ants. The white flies are also visible to the naked eye as a cloud of small white-winged insects about 1.5mm long. They are very small but usually invest plants.
Whiteflies affect both plants in a greenhouse or indoors and also those outside in the garden. They thrive in warm conditions so you find them in the summer in your garden but year round in your greenhouse.
What to do
Check your plants for whitefly from spring onwards. You can trap the flies on sticky yellow sheets hung among the flowers in greenhouses. It doesn’t help with the whiteflies coming to your plants but it catches them when they do.
Once again, for pesticides, start with organic sprays such as natural pyrethrum or plant oils. Remember to apply them regularly. If using pesticides, choose one labelled for whitefly as I have noticed they have become resistant to some pesticides.
Scale insects love a huge range of plants and flowers and they have been covered in many guides on this site. With more than 25 species in Britain and more in the USA, you’ll probably see at least one kind in your plant’s life. Scale insects in their adult form have a waxy, shell-like covering and you can see them on your passion flower’s leaves and stems. Look in particular on the underside of the leaves for these bumps.
They suck the sap of your plant’s leaves, weakening it. And they leave behind the sweet honeydew substance that forms a base for black sooty mould to grow just like aphids do.
What to do
Check your passion flower plant regularly for scale insect bumps. If you find just a few, you can just remove them by hand.
The best time to treat an infestation is in the middle to late summer when the scale insects are more vulnerable. Encourage the scale insects’ predators to make their homes in your garden. Ladybirds/ladybugs and some birds feast on these insects.
As always, try a natural organic spray before the heavier pesticides. Natural pyrethrum or plant oils should be applied regularly as they lose their potency over time. I have noticed it takes a few applications of sprays as their waxy shells seem to help protect them from sprays.
And never spray pesticides on plants that are in flower. You may harm bees and other insects that work as pollinators.
Mealybugs are yet another sap-feeding insect. These, however, are found on passion flowers that you keep in your home or in a greenhouse or conservatory. They love warm conditions. Once again, these insects weaken the plant and leave behind the sticky honeydew.
Mealybugs live together in groups in the parts of the plant that you don’t really see. They can live in leaf sheaths and under loose bark, and even on plant roots. You probably notice them by the sticky honeydew they leave behind that becomes covered by black sooty mould.
What to do
Mealybugs don’t move far so any infestation is usually brought in on another plant. Check carefully each new plant you bring into your indoor space. If possible, keep each plant in quarantine for at least a month to see if mealybugs appear.
Although a plant may have only a few mealybugs and may seem to be OK, these insects quickly build a dense population. Remove the parts of the plant that have visible mealy bugs on them, place the plant in isolation and keep watch for more mealybugs to appear.
Unfortunately, it’s difficult to remove a heavy infestation of mealybugs. So be prepared to discard the entire plant to avoid the bugs spreading.
Passion flower diseases
Cucumber mosaic virus
This is a common plant virus so it’s not exclusive to passion flowers. It causes the foliage to become deformed and to become yellow. The leaves curl downwards and are reduced in size. White streaks may appear in the blooms of the plant.
The result is a plant whose growth is stunted. Even if your plant is looking good in the spring and summer, it could fall victim to this virus.
This virus is usually transmitted by aphids. However, it can also be taken from plant to plant on garden tools and people’s hands.
What to do
Keep your hands/gloves and garden tools clean and sanitised at all times. If you handle an infected plant, sterilise everything that’s come into contact with it.
Destroy any plants that look as if they’re infected with the cucumber mosaic virus as soon as you notice them. As it’s easily transmitted you want to contain any potential outbreak.
See the section above on what to do to control aphids.
Leaf spot disease on passion flowers
Leaf spot is another disease caused by a fungus. It’s not fatal but it does spread quickly. You need to catch it in its early stages and deal with it decisively.
Leaf spot first appears as brown spots on the underside of older leaves. Look at the leaves at the bottom of the plant. Also check the stems as well as the blooms. The leaves will turn yellow and eventually dry and fall off the plant. Without foliage, the plant has no energy to develop further leaves and blooms.
What to do
Remove any infected leaves when you notice them. Wash your hands and any garden tools that have come into contact with the infected plants before you move on. This disease spreads easily.
Consider organic fungicides such as potassium carbonate or copper sulphate. Follow the instructions of the product but start spraying as soon as you notice the problem.
You may have to move to chemical fungicides if the problem worsens. Be careful how you use these as they do not kill selectively. A general fungicide labelled for black spot usually works.
Root rot is another very common disease. It’s the result of poorly drained soil. The roots start to rot and this works its way up the plant. Everything becomes soft and squishy. The leaves become yellow and may drop off, which is one of the signs, as well as wilting stems. And no matter how much you water the plant, it always looks like it’s wilting. The plant is unable to create the energy it needs for its growth and development.
What to do
Uncover the roots of the plant and separate them out to dry out. Check which roots have rot in them and which ones are OK.
If you think you can save some of the roots, dig up the plant then wash the roots. Then cut off the diseased roots with a sterilised knife. Remove the water-logged soil from around the plant and replace it with a mixture of organic compost and horticultural grit to improve the drainage of the soil as this is usually the cause. The soil must be able to drain well but not too quickly. Replant the plant.
If you can’t adjust the soil to what the plant needs, then transplant the plant to another part of your garden or consider growing it in a pot or container. See Passiflora caerulea – growing and caring for passion flowers for information on the growing conditions that this plant needs.
If most of the roots of the passion flower plant are rotten, then you must destroy the plant.