Before you select a biocontrol, it’s important you understand the pest problem at hand to ensure you select the right predator control.
What do aphids look like?
Of the 500 varieties of aphids, the most common ones that plague British gardeners are black and green aphids, also known as blackfly and greenfly.
They are usually around 4mm in length with a bulbous abdomen. Some may have wings and others are wingless.
If you see aphids with wings in spring or summer, it may be because the environment has become too crowded for them. Aphids produce offspring with wings when this happens, so they have the ability to fly off and look for a new location to feed.
Aphids have a stylus – a syringe like needle used to pierce and suck sap from the plant. They also have two tubes on their back to excrete honeydew.
Where am I likely to find aphids in my garden?
You may only notice aphids once they have become a problem. This is because they reproduce extremely quickly - a single female aphid will produce up to 80 new aphids, so they can rapidly overwhelm a plant.
Aphids like to feed on the underside of leaves and on new buds. Rose gardeners will be familiar with their rosebuds being taken over by aphid populations in spring.
Aphids often appear on new green foliage. If you have used a high nitrogen fertiliser to encourage foliage growth on a particular plant, you may notice this is where aphids will reside. They will also cluster around stems in large numbers.
Aphids will settle on many different plant types including flowering plants, ornamentals, climbing plants, and fruit and vegetable plants.
Ants ‘milk’ aphids for their honeydew, so if you notice ants running up and down the trunks, branches and stems of your plants, you may well have aphids somewhere on that plant.
What damage do aphids do to plants?
In small numbers, aphids are not normally harmful. However, large quantities of aphids can weaken and even destroy whole plants – especially smaller plants like annual flowers and shrubs.
Aphids damage the plant by sucking sap from it. This can lead to leaf curl, discoloration and yellowing, and stunted growth. The damage can significantly impact the visual appeal of plants and trees.
Aphids excrete a sugary liquid known as honeydew. This honeydew can make leaves sticky; you may notice leaves that look glossier than normal as a result of patches of honeydew.
This honeydew can attract black sooty mold. This mold is not a parasite, but it can stress the plant by blocking out light and preventing its ability to photosynthesise. This can stunt the plant’s growth and lead to leaf shed.
What is the best way to get rid of aphids?
- Be vigilant in spring and inspect your plants, especially those putting on fresh green growth.
- If you see a few aphids, the best way to deal with them when they initially appear is to squash them by hand or blast them off with a spray of water. Hopefully this early intervention will prevent them from continuing to expand in numbers.
- If you have large volumes of aphids, or an infestation on a plant that must be saved, use a biological control like ladybird larvae or lacewing larvae.
- Discourage ants when using biological controls for aphids as they will defend the aphids, attacking and driving off any natural predators by biting them and spraying them with formic acid. Try blasting the ant trails with water or use a biological control for ants’ nests if you can see where this is.
How do biological controls for aphids work?
- There are two main controls for aphids, ladybird larvae and lacewing larvae.
- Ladybird larvae will target both greenfly and blackfly and are suitable for organic production.
- The larvae of ladybirds and lacewings feed on the aphids, consuming up to 100 aphids each a day.
- Ladybird larvae will not move too far from where they are deployed which makes applying them highly effective.
- Adult ladybirds will continue to consume aphids giving you long-lasting control.
- Ladybird larvae can be deployed when the temperature is above 10°C. Lacewing larvae can be used when the temperature is above 15°C.
For more informaiton, read our Guide to Biological Controls here.
How do I use ladybird larvae?
- Ladybird larvae will perform well in greenhouses and polytunnels but will also work in outdoor settings too.
- Larvae should be used between March and September for indoor use, and May to September for outdoor use.
- The larvae will arrive in a sachet. Simply deploy them on the affected plant. Full instructions come with the larvae on delivery.
- Do not use sticky traps with larvae.
How many larvae do I need?
- Ladybird larvae should be applied at a rate of 10-20 per square metre. This equates to around 5 larvae per medium sized plant.
- Our packs will cover around 20 square metres.
- You may need to reintroduce the larvae at 2–3-week intervals as the larvae will develop into adults in around three weeks.
- Delivery of live organisms is sensitive so please take care to follow the delivery and receipt of product information on our web pages.
If you have any questions or concerns about using biological controls for aphids, please get in touch with our technical team for free advice.
