After the cucumber vines were treated for mildew, they greened up a little but didn’t really bounce back. Today the culprit was discovered… Black aphids all over the undersides of the leaves and in the flower buds.
There’s too many here to squash, the way you can do with rose buds. These little buggers will need to be sprayed. My favourite organic pest spray is simply crushed garlic soaked in water, as described in the cabbage white post.
In a more advanced garden, there would be more predator bug species around to slow these guys down. Plants like nasturtiums and marigolds can also be planted around to draw helpful insect species like lady bugs, lace wing flies and hoverflies. Birds and spiders can also help keep things in check.
A concentration of sap sucking insects on the flower buds can damage the growth and reduce fruit and veggie yields. It is possible to hose the little buggers off. They don’t move around a lot and will die back if they’re hosed onto the ground. This didn’t work on the cucumbers, though, because the flowers were also being knocked off. On roses, running your fingers over the buds and young leaf stems can squash most of the aphids and control them long enough for predators to do their job.
Edit: On the entrenched infestation of aphids on that cucumber vine garlic spray alone didn’t save the vine. In this case a stronger spray of garlic and chilli with some soap added, would be needed to keep them in check.
In addition to the garlic spray, a mix of baking soda might also help. A couple of teaspoons of baking soda (sodium bicarbonate) and the same of soap powder in a litre of water will deter aphids and many sap suckers. Derris dust is another plant based pest treatment but like pyrethrum it will also affect the “good” bugs that you want to keep around.
There are a few things that can make plants more attractive to sap sucking pests like aphids. Mono-cropping, or having a whole garden bed devoted to one type of plant, makes it much easier for a pest to mow through them all than if you plant a variety of different things and include companion plants. Aphids also like humidity, so keeping some mulch on the ground and watering the soil rather than the plant can help keep their numbers down. Lots of nitrogen rich fertiliser will also encourage bugs as it causes the plants to grow very quickly, with soft, watery, sweet growth. Balancing the nitrogen with potassium and phosphorus in potash, bone meal and fish emulsion or reduce the fertiliser in place of well composted manure and plants will grow stronger and better able to resist pests.
These few simple guidelines and a bit of garlic, chilli, soap or soda on standby mean there’s really no need to resort to using toxic chemicals on your home grown food. It helps keep your family and the planet that little bit more healthy.