Estonian expert: bury garden waste 30 cm deep before frost to curb slugs

Eha Krūsa, a plant protection specialist at the Estonian University of Life Sciences, recommends that gardeners bury all garden plant waste at least 30 centimetres deep before the first frosts. The aim is to limit the spread of black slugs, whose eggs spend the winter in the soil and tolerate cold well. The advice was reported by the Estonian public broadcaster ERR.

Slugs are still feeding

Speaking on the radio station Vikerraadio, Krūsa said the temperature is not yet low enough to send Spanish slugs or black slugs into their overwintering phase, so they are still feeding. She noted that, unlike the Spanish slug, the black slug is not regarded as a particularly dangerous pest. Even so, large numbers can cause considerable damage to plants. The species has few natural enemies and can multiply quickly.

A sharp rise in black slug numbers was observed this summer. The expert explained that slugs thrive in damp weather, and they began appearing in large numbers in the second half of July, as well as in August and September.

What to do during autumn tidying

Eggs or young slugs in hidden corners of the garden are fairly hard to spot, but larger slugs can be effectively collected by hand. Krūsa stressed that every slug removed helps limit reproduction. During autumn cleanup she also advises gathering the small, white, transparent eggs found in plant remains or on the topsoil.

Black slugs usually hatch only in spring and spend the winter as eggs. According to the expert, the eggs resist cold because they contain very little water. Fallen leaves serve as food for adult slugs.

The compost heap can still be turned once or twice at this stage. This is especially effective after the first frosts, while the compost has not yet frozen through. She also suggests digging a 30-centimetre-deep hole and placing all plant waste in it. In her words, slugs will not hatch from the buried eggs, and a layer of soil about a spade's depth can prove fatal to them.