There’s a pest for all weathers, with winners and losers during this long dry spell.
Every organism is a food source for another. When one population increases, its predator numbers rise to take advantage of this extra food supply.
Aphid numbers rise rapidly during a warm dry summer. Being parthenogenetic, an initial mating leads to a rapid rise in population. Once it’s 10 days old an adult aphid produces up to 10 babies every day for the rest of the season, so aphids should be poised to take over the world.
But fortunately, their predator numbers rise to control any surplus. What was described as a plague of aphids in 1975 led to a surge in the ladybird population. But in 1976, there were too many ladybirds for their available food. These effects weren’t immediately obvious, but this kind of population boom and bust is not unusual. But predators generally don’t empty the larder.
Other organisms exploit their hosts differently. Ants milk aphids, extracting honeydew for their young and shield greenfly from attack by other predators. They move them to new plants and sometimes even take aphids back to their underground nests to feed on plant roots. These aphids are almost like in-house milking cows.
Ant nests may be troublesome in dry borders, undermining already stressed plants, and they can even create little, mole-like heaps of excavated soil on lawns. If ants become a serious nuisance, discourage them by soaking the ground. Or pour a bucket of water over a nest if you find one in the compost heap.
Although there are quite a few ‘offenders’ in a distressingly dry garden, fortunately the mollusc brigade is finding the going tough. Up to half the body weight of a slug is water and they can’t prevent it evaporating through their skins. This can happen quickly. I’ve seen some specimens that had expired trying to cross a concrete slab during a warm evening.
Fortunately, Deroceras reticulatum, those nasty little beige jobs, have been scarce but just you wait for the rain. They’ve burrowed down around 30cm in the soil and will reliably reemerge when conditions improve. Get beer traps and organic slug pellets ready to greet them.
Sadly, the larger Arion species aren’t as troubled. With thicker D-shaped bodies and proportionately less skin, they lose less water. I see them huddling together under mulches, where they’ll reduce water loss by up to 34%. Alternatively, the young ones slither into a suitably moist potato, ready to end up as a surprise treat for my ducks. This is the first year I’ve seen slug damage in white new potatoes, but luckily red Duke of Yorks don’t feature on their menu.
Slugs lay eggs in the soil in summer or autumn, hatching out in winter or early spring and inevitably our recent run of cool, wet summers has ensured an overly healthy population. Since the soil is parched this year and many fewer molluscs are on the go, there should be fewer specimens next summer. At least, let’s hope so.
Unfortunately, snails are less badly affected by drought. They aestivate by secreting a mucus film that forms a seal over their operculum or opening. They also congregate in cool places till the rain comes. Unlike slugs, they live for more than a year and individuals breed more than once.
But it’s been a much better year for insects. I’ve seen a Common Blue butterfly for the first time in several years, and was delighted to find a Red Mason Bee, voted Scotland’s favourite insect in a recent Buglife poll, had converted 2 holes in the frame of our lounger into egg cells.
Plant of the week
Fuschia ‘Lady Thumb’.. Pretty dwarf fuchsia growing to only about 60cm. Carmine pink sepals and white petals from which protrude pink stamens. The foliage is neat and a good dark green. Perfect in pots.
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