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03 Aug 2023

Trinity Hall’s lawns face a new enemy: the chafer grub. Luckily there’s a biological friend we can use, the nematode worm, to help protect out grass. Head Gardener, Samantha Hartley, explains.

“Cambridge colleges are famed for their beautiful emerald-striped lawns. But, in recent years, we have been invaded by the European chafer (Phyllopertha horticola and Hoplia philanthus) who lays her eggs deep in the soil under the lawn.

“When the eggs hatch, the hungry grubs begin eating the roots of the grass. Birds then peck at the lawn to uncover the fat juicy grubs and sadly, since the roots are damaged, the whole lawn comes up like the lid of a sardine tin.

“To combat this problem we use microscopic nematodes (Heterorhabditis bacteriophora), a kind of eelworm, which infest the grubs and kill them. We will be applying them at a rate of half a million per square metre. But not one at a time!

“The current dull and damp weather is ideal for this as we need plenty of water to wash them into the soil, and they don’t like sunlight either.”

For more on chafer grubs see the RHS website.