Green way to defend your garden ...with a microscopic army
ON A recent pest patrol in my garden, I found a number of scale insects on the stems of an olive tree after noticing some leaves were turning yellow. In the past, I might have been tempted to spray with an organic pesticide but instead, I decided to tackle the sap-suckers by placing an online order for a biological control.
Now, I know that might sound as if I’d tried to get my hands on a dangerous substance developed at Porton Down, but the package that arrived in the post a few days later was completely safe to handle.
It housed a carton containing an army of predatory, microscopic creatures known as nematodes that were transported in a white powder. Once mixed with water, the contents were sprayed on to my olive tree. Over the next few weeks the nematodes should enter the scale insects and kill them from the inside.
It’s too early to say whether the nematodes are having an impact on my pest problem, and the supplier recommends the process is repeated twice more at 21-day intervals. However, I’ve had great success with other biological controls in the past and am expecting similar results from this one.
Biological controls have been used in commercial horticulture for decades and have been sold to amateur gardeners for about 30 years. Essentially, they are a way of controlling slugs, caterpillars, red spider mites, leatherjackets and many other pests by using their natural enemies, parasites or predatory creatures.
Among plant protectors available are phytoseiulus mites, used to combat red spider mites, and lacewing larvae, which eat aphids.
After they are introduced, the mini-beasts breed and increase in numbers until pest populations are brought under control.
Most are specific to the pests and don’t harm other creatures.
Some biological controls are designed to work outdoors, while others are better suited to greenhouses. For example, if your indoor plants are infested with common whitefly, it’s possible to control them by releasing a squadron of tiny wasps called Encarsia formosa, which will lay their eggs inside whitefly larvae.
As some biological controls need to be stored in a fridge or have an expiry date, they are generally sold directly via online specialists and not kept in stock by garden centres. Suppliers include Defenders (defenders. co.uk), Dragonfli (dragonfli. co.uk) and Nematodes Direct (nematodesdirect.co.uk).