Allium leaf miner is a new entry in a chart of the top 10 worst plant pests.

It’s partial to members of the onion family, with small white maggots boring into the foliage and stems of edibles such as leeks, onions, chives, shallots and garlic, rendering crops inedible.

When they’re fully fed, maggots turn into brown pupae which can often be found in stems of crops.

The problem came to light when the Royal Horticultural Society released its list of the top 10 garden pests of 2014.

Allium leaf miner was first found in the UK in 2002. Now, the RHS says it has become a “serious threat” to crops.

The RHS said: “This pest is likely to spread to new areas over the coming years. Gardeners can protect plants by growing crops under horticultural fleece.”

Rosemary beetle (5th) which feeds on foliage of aromatic plants such as lavender, sage and thyme – and tortrix moth (=8th) made a comeback to the top 10, after a short absence.

Slugs and snails again took top position on the list of the most problematic pests, as they have done for eight of the last 10 years.

RHS senior entomologist Dr Andrew Salisbury said the RHS saw a 42 per cent rise in enquiries about pests in 2014, compared to 2013.

Andrew explained:“It’s interesting that pests affecting food crops were very prominent in the 2014 list.

“Perhaps this reflects a trend for gardeners to set aside some space to increase their food self-sufficiency and grow crops.”

TOP 10 PEST ENQUIRIES TO THE RHS IN 2014

1 Slugs/snails
2 Vine weevil
3 Cushion scale
4 Lily beetle
5 Rosemary beetle
6 Aphid
7 Allium leaf miner (fly)
8= Tortrix moth caterpillar
8= Mice/voles
10 Ants