Getting rid of your garden pests

Some of the most common pests that damage plants in Greek gardens can be eradicated without the use of harmful chemicals. Piers Goldson, a horticulturalist from Wales currently working in Greece for the Mediterranean Garden Society at its headquarters in Sparoza, in eastern Attica, talked to Kathimerini English Edition about some of the pests he has encountered since working in gardens in Cephalonia and Attica, suggesting ways to deal with them that are environmentally friendly. One of the most commonly encountered problem is scale (Coccoidea, or kokkoideis in Greek) a large group of tiny insects comprising thousands of species. «Scale occurs all year around on a lot of glossy plants, such as Arbutus unedo, (strawberry tree, koumaria in Greek) Laurus nobilis (bay, dafni) and Ceratonia siliqua (carob, haroupia) in cultivation. In the wild, you generally don’t see that many pests. They are mostly found in gardens where plants are out of their natural habitat and under stress,» explained Goldson. «Scale is often found in balcony gardens and usually comes in on a new plant. Scale insects, which lie underneath leaves, are usually circular and smaller than a lentil. They can be dealt with using a horticultural soap – Savona is one brand name. Some people use a detergent solution, but you have to be careful about the quantity. Ecova is a plant-based detergent you can get from health food stores.» «If the problem is on house plants, methylated spirits on cotton wool works well – but test it on a leaf first to see that it doesn’t burn it. I’ve used it before to treat a whole plant which I then hosed down. Death is usually instantaneous with this treatment. Horticultural oils are also good.» Another problem Goldson has encountered in Greece is with mildew, which is often found where there are sprinkler systems. «A moist atmosphere encourages things like that, especially if the watering is at night. Mildew can be treated with milk or baking soda in a solution of water.» «The cypress canker, also known as bark canker (Seridium cardinale, elkos kyparissiou) is a fungal parasite that attacks cypress trees all over the Mediterranean basin. It is usually seen in a sunken area, or on a branch which is cracked and oozing resin. When that canker totally circles a branch or twig, anything above it just withers and dies. It is also spread by rainwater. You can cut it out, or cut off the branch into a healthy area below the canker and then burn the diseased part. Sometimes it can be close to the trunk, which is a problem, but tree surgeons can remove it. This basically involves chiseling away with a scalpel until you get to good wood, which you disinfect and cover with a wax or rubber solution. In Italy they have created cypress clones which are resistant, but I don’t know if these are available in Greece. But we buy so many plants from Italy anyway that I’m sure pressure from consumers and nurserymen could get these resistant clones (Cupressus sempervirens Bolgheri or Agrimed No.1) here,» he said. Apart from the olive fruit fly, another problem with olive trees is the «knot» (in Greek, karkino tis elias – literally olive tree cancer) caused by the bacteria Pseudomonas savastanoi that creates rough swellings up to 2 inches in diameter. «These also circle the branch and then everything beyond that withers. They can be removed with pressure washing (with a powerful hose); they generally have little feeding tubes that need to be blasted off. Another alternative is Bordeaux mixture, a copper-based fungicide,» said Goldson. This is also a problem seen on plum, cherry and almond trees, again spread by water. The olive knot spreads in winter, and is quite a vicious bacteria that enters plants through leaf scars – cracks left when the leaves drop. Goldson said it is best to remove it in the summer when it is dry and wounds have healed, before the water gets a chance to splash the bacteria around the wounds. Another pest, and one that that is harmful to humans and animals, is the processional caterpillar (Pytiocamba). «Processional caterpillars make large nests in pine trees and are a major irritant to humans and animals, causing large swellings and rashes, so under no circumstances should you touch them, but wear full protective clothing, glasses and a hat. They can be destroyed by spraying them with Bacillus thuringiensis, also known simply as BT, a biological insecticide (brand name Dipel). Then you can burn the nests. However, it is too late to deal with them this time of year, as you have to get them when they are feeding on leaves. To treat them, you mix the Bacillus with a bit of sugar and it sticks it to the leaves. The bacteria which kills them is itself killed by ultraviolet light, so you don’t want to do it in the middle of a sunny day, but in cloudy weather. The caterpillars will come out, feed on the bacillus and shrivel up and die. What you don’t get with that treatment, you will have to cut out and burn.» A good explanation of the way pests enter a garden and an introduction to the holistic approach to dealing with them can be found in the relevant chapter of Jennifer Gay’s «Greece: Garden of the Gods» (Athens News 2004).