As the warmer weather becomes a breeding ground for all kinds of leaf-destroying bugs, plant-owners should be warned to make these crucial checks
As we make our way into spring, we can look forward to brighter days, milder weather and blooming flowers – but it’s not all good news for plant-owners.
The more pleasing climate also means an increasing number of flower-chewing insects are crawling out of the woodwork. So, which ones do you need to look out for?
1. Aphids
Also known as greenflies and blackflies, aphids are small sap-sucking bugs that are particularly drawn to green, young plants. Since they prefer warm weather, they tend to be more pervasive in spring and summer – though they can appear on indoor plants all year round.
One or two are rarely an issue, but a large infestation can cause diseases to spread. This can lead to streaked, mottled and unsightly leaves.
If you’ve spotted a crowd on your plants, Gardener’s World advises: “Often simply hand-squashing a small infestation is all that’s needed. Be alert for early warning signs and inspect plants thoroughly – greenfly and blackfly can be hard to spot as they nestle in leaf joints and on the undersides of leaves, and often the first warning sign on indoor and greenhouse plants is the sticky honeydew on the leaves beneath the initial cluster.”
2. Scale insects
These tiny creatures are no more than 6mm long and have waxy, grey-brown shells. Don’t be fooled by their muted appearance, though. They can wreak havoc on your house plants. Scale insects are known for secreting a sticky, sugary substance (called honeydew) which creates an optimal environment for the growth of sooty mould.
If you spot these dark patches on your leaves, the first port of call is to physically remove the bugs. Gardener’s World writes: “First try to remove them with your thumbnail. If there are too many, use an insecticidal soap spray. Alternatively, leave them for the birds to pick off. In a greenhouse, use the parasitic wasp, Metaphycus helvolus, bought by mail order as a biological control.”
Alternatively, you can try using pesticides containing the insect-killer deltamethrin for more ornamental plants, or a less harsh organic fatty acid spray on fruit brushes and trees.
3. Thrips
Also known as thunderflies, immature thrips are whitish, about 2 mm long and flightless. Once they reach adulthood, they turn brown-yellow or black-brown and have two pairs of wings. They like to feed on the upper surfaces of leaves and flowers and you may need a magnifying glass to spot them – but a sure sign they’re present is that they leave plants looking dull, mottled and streaked. Sometimes they can even leave speckles of ominous-looking black spots.
Plants commonly affected include honeysuckle, peas and onions. Thrips are also known to thrive in hot, dry conditions, so to prevent an outbreak you should increase the humidity.
But what to do if you have an infestation? According to Gardener’s World: “Under cover, a biological control – which is the use of a specific living organism, such as a parasitics wasp, to predate on a pest – is an environmentally friendly and effective way to tackle pests. This can only be used in any indoor environment, not outdoors. Thrips can be combatted with several species of predatory mite including Amblyseius .” For a chemical solution, you can also use the insecticide acetamiprid.
4. Mealybugs
Soft-bodied and roughly 4 mm long, mealybugs like to feed on the sap from succulent plants like cacti. Their appearance is quite distinctive thanks to their white, waxy secretion, though they tend to congregate in more hidden leaf axils. In large numbers, they can debilitate plants and their sticky sugary secretion can also lead to the growth of sooty mould.
To combat an infestation of mealybugs, you can try moving plants outside so birds will eat them. You can also try introducing ladybirds as a natural predator. On cactuses, small infestations can possibly be removed with tweezers. Otherwise, you can try spraying plant leaves with fatty acids.
