The good, the bad and the ugly of garden critters
Grant Douglas offers some less harmful ways to deal with unwelcome guests in the garden.
Every garden has many guests of the creepy-crawly, fluttery, buzzy and slimy-slithery kind. Some are welcome but others we wish hadn’t turned up. Sometimes the welcomed ones deal with the unwelcome ones.
The first tool in the box of dealing with unwelcome ones is a little knowledge and observation; knowing what they look like and what damage they do. Often damage is the only sign that a pest is present, as the pest itself is too small to be easily seen with the naked eye, and only when you notice the puckering of the leaves of a capsicum seedling will you realise that aphids are present.
Once you have found unwelcome guests in the garden, you have two options: either deal with them or let nature take its course. I prefer to use a combination of the two. Often, depending on what pest is present on which plant, I will let natural systems take over, but if the damage is severe, or the future consequences drastic, I will interfere to clean up the problem.
I choose an organic/minimal-environmental-harm method when interfering – an approach that will have the least effect on other organisms in the garden and the environment. This is reflected in my recommendations of what to use as controls.
If you don’t choose to take this approach, as long as you have correctly identified the pest, then finding conventional remedies is easy. They are widely available.
One of the largest groups that gardeners have to deal with are the sap suckers. Sucking the sap from a plant distorts its growth, especially in the growing and fruiting tips, causing everything from aesthetically unpleasant shapes, to lack of growing and flowering buds, and vigour, that can stunt growth severely enough that plants will not produce.
The other consequence of having large numbers of sap suckers on a plant is the presence of sooty mould. After sucking the sap of the plant, sap suckers exude honeydew (their waste product), which the sooty mould feeds on.
So to prevent sooty mould, you must find out what sap sucker is causing the honeydew. Is it passion vine hopper, scale, white fly ... ?
My least favourite sap-suckers – and how to deal with them
In our garden, aphids are mostly kept under control by our tauhou (waxeyes), but the aphids cause a problem when they invade seedlings in the greenhouse or cloches, particularly early capsicum and tomatoes. Tell-tale signs are a crinkling of the leaves, white discarded skins under the plant, or the aphids falling off when you shake the plant.
If only a couple are present, then thumb and forefinger squashing is usually sufficient, but if numbers build up, I use pyrethrum sprayed in the cooler part of the day, as it can cause burning to young tips, especially on very young tomato plants. Soapy water works, but not as well, and has less risk of burning.
I have not had success with companion underplanting, and in most of the alternate sprays (garlic, chilli) the effective ingredient is the surfactant (soft soap) which sticks and smothers the insect.
A note on pyrethrum – although it is a natural product, it is still toxic and should be used carefully by the user. It will also kill beneficial insects if it comes into contact with them, so avoid use if they are around. The advantage of it is that it works only as a contact spray, with low residue, so doesn’t persist in the environment.
Spittle bug: Unfortunately, the tauhou does not enjoy sticking its beak into the spit surrounding this small insect. So digital methods (thumb/forefinger) work on small numbers, or pushing the nozzle of the sprayer into the spit, using pyrethrum, is effective if numbers are high.
Fluffybums: Small insects with fluffybums that flick when touched and that are the nymph (juvenile stage) of the passion vine hopper, which can be invasive on certain plants later in the season (dahlias, passion vine and others, especially if grown under the eaves, out of the rain and wind). They cause sooty mould, but pyrethrum is effective in controlling them.
Shield (stink) bugs: The green shield bug starts life as a small spotted black bug and can cause considerable damage to beans (distorting shape/drying out), tomatoes (hard spots on fruit) and other vegetables, but can be controlled by pyrethrum.
White fly: The main effect of these is reduced vigour and sooty mould on leaf and fruit on greenhouse crops. Reduction of numbers can be achieved by good ventilation and spraying water under the leaves, and the use of yellow sticky hanging cards. They are seldom a problem outside, but if numbers build up in the greenhouse, neem and pyrethrum are effective, but because of the extremely short life cycle of the white fly, two or three sprayings, three days apart, may be necessary to gain control.
Other unwelcome guests
Greasy cut worm: A devastating soil grub of a moth. It emerges from the soil at night and chomps off seedlings at the base and then re-enters the soil. Dusting with Derris Dust (use carefully) is effective, as is digging around cut-off plants, early in the morning, where you will probably find the grub, not very deep, and deal with it as you want.
Slugs and snails: Encourage blackbirds and thrushes into the garden, but in enclosed spaces, where you may have seedlings or cuttings. Non-toxic commercially available slug-bait is effective, as are saucers sunk to ground level and filled with beer (it doesn’t have to be the latest craft brand) – what a way to die!
Caterpillars: Many caterpillars of moths and butterflies (white, especially) can be a problem, ruining brassica crops and others. Insect netting can be used, although it’s sometimes inconvenient. But the use of bacillus sprays (a non-toxic biological insecticide) or pyrethrum works well.
These are just a few of the unwanted guests in the garden. Others, such as scale (regular oil sprays) mealy bug (pyrethrum), carrot fly (netting/timing), all have their controls, and some of them are by beneficial insects – the welcomed guests.
Top of the list of these are the honey and bumblebee. Without their presence in the garden, most of our fruit and flower plants would not produce fruit and seed.
This year, due to late frosts, our resident bumblebee population was reduced, and as they are the only insect that can pollinate broad beans, our crop is later than usual.
By providing a large variety of different flowers, we encourage bees to forage, and, for the bumblebee, mulch on the ground and heavy plant cover will give them overwintering habitat.
Pollination is also provided by many flies and solitary bees and wasps. So don’t be too quick to judge what is sitting on your flowers – it may be doing a valuable job.
Ladybirds are the most colourful of our welcome guests, and are very beneficial. Learn to recognise their nymph stage, which looks nothing like the adult (more like a tiny grey and orange lobster). They will eat lots of aphids each day. Our swan plants, covered in orange aphids, were cleaned up by nymphs and adults in a few days. Avoid using insecticides if they are present.
With praying mantis, it is difficult to decide if they are welcome or not. Although they consume many pests, they also will eat honey bees and monarch butterflies, and the South African variety (slim/silvery) will eat native ones (blue patch near front knees). Spiders should be tolerated – at least to a certain level, as they are very capable of dealing with many pests.
Much beneficial life in the garden lives in or on the ground. Slaters, beetles, millipedes, worms all do their best to convert organic matter into humus that enriches our soil, as do the microscopic fungi and bacteria, if we provide the right conditions – plenty of organic material on the ground.
The more you encourage balance in your garden, and view it as an organic whole, the less you will need to intervene. Sometimes you will need to, but if you do, do it in the least invasive way, causing minimum harm to the garden’s ecosystem, and the garden will thrive.