Plant Doctor Archive

Diseased cucumbers

FOR many years I successfully grew tomatoes and cucumbers in my greenhouse, but for the last three my telegraph cucumbers have succumbed to a mystery disease. Can you identify the problem? I grow the tomatoes on the outside row in the greenhouse with the cucumbers on the inside.

YOUR samples didn't arrive in good enough condition to positively identify the problem. However, there are a range of fungal and bacterial diseases that affect cucumbers which could cause this type of problem.

As a basic rule, to reduce the risk of soil-borne diseases in cucumbers you should avoid growing them in the same soil for more than two or three years. So it sounds as if you should stop growing them in the soil and plant them in bags or large pots using a good quality potting mix. You'll need to adjust your fertiliser and watering regimes to suit the new mix. They'll probably need more regular watering, as potting mix dries out more readily than soil. But it should reduce the disease problem, especially if you isolate the pots from the soil with a sheet of plastic.

Alternatively, if you want to continue growing in the soil, you could try using a product such as Basamid, which helps control soil-borne pests and diseases. Follow the label recommendations carefully.

Either way, bear in mind that most cucumber diseases are worse in cool, wet conditions, so try to avoid watering or wetting the foliage when the weather is cool and cloudy. To further reduce the chances of infection, you could spray with fungicides like Bravo and Champion Copper or copper oxychloride.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.