Snails in canola can be controlled by adjusting liming and other fertilisation programmes, and by applying trace elements and biostimulants, according to a microbiologist.
By Amelia Genis, senior journalist at African Farming and Landbouweekblad
Speaking at SSK’s annual grain day at Uitkyk near Riversdale, Randolf Meyer, a microbiologist at Revival Crop Nutrition, said that conservation farming offers many benefits but can also create ideal conditions for snails.
Why Conservation Farming Attracts Snails
“Snails like a moist environment with soil cover, so no-till systems are ideal for them,” he said.
This did not mean that farmers should plough and burn their fields, he added, but rather that they should adjust their crop residue management practices to prevent such problems.
Snails also need the free lime from calcium carbonate – commonly used in soil amendments – to build their shells. Amendments are often made without placing the calcium carbonate deeply enough, he said. As a result, a lot of free lime remains in the topsoil layer. “Calcium carbonate leaves snails with a pantry full of shell-building material.”
Farmers often also apply a highly soluble phosphate source such as mono-ammonium phosphate (MAP) together with lime.
“You get calcium phosphate when the phosphate from MAP and the calcium from lime react,” Meyer explained. “This locks up the phosphate, leaving no available phosphate for energy production and protein synthesis in plants.
“When protein synthesis is deficient, plant material becomes a favourable nutrient source for diseases and pests.”
Also read: Smarter pest management essential for potato sustainability
He added that applying large volumes of single nutrients to correct deficiencies can displace other essential elements – for example, adding too much calcium can cause potassium and magnesium deficiencies.
The potassium-to-calcium ratio in plant sap should be about 4:1, Meyer said, and in the soil it should be the other way around.
“In the soil we want more calcium because it improves root penetration,” he explained. “If potassium levels in plants are about four times higher than calcium, they form starch and polysaccharides more easily and become less susceptible to diseases and pests.”
Also read: Winter grain farmers spend millions on massive slug problem
Sustainable Solutions For Healthier Plants
Meyer recommends applying smaller volumes of lime – preferably microfine lime granules applied annually – or using gypsum as an alternative calcium source.
“Fertilise and correct phosphate levels with a calcium phosphate product that releases phosphate slowly and is not immediately water-soluble,” he advised. “It should also contain phosphatase enzymes to release both calcium and phosphate.”
He further suggested that farmers catalyse nitrogen applications with biostimulants to ensure all free nitrates are converted into amino acid metabolites through biological processes.
In addition, farmers may prefer to spray plant enhancers and trace element supplements rather than rely solely on pesticides.
“Ultimately, it is more sustainable to make plants resistant to pests through metabolic and nutritional processes than to wage war against pests with chemical pesticides,” Meyer said.
Also read: Pesticides ‘essential part of farming’
