3 Hungry Beetles to Watch Out For

Last week Barbara Pleasant reported on that nemesis of the spring vegetable gardener: flea beetles. What a timely article that was! A quick check in my garden confirmed the first pitted holes in my radish leaves, the telltale sign that these high-jumping rascals are already present in my garden. I should have been more diligent with my crop covers. I’ve only myself to blame.

The flea beetles’ on-cue appearance got me thinking: If I had to pick three beetles I really wouldn’t want to find in my garden, what would they be? Let me introduce you to my terrible trio of beetles...

1. Asparagus Beetle

First up is the asparagus beetle, an insect with a discerning palate based on its preference for what I consider the very finest vegetable of all! The adults (shown in the picture at the top of the page) are dedicated followers of fashion too, with a handsome reddish thorax and distinctive yellow or white accents on their wings. Their larvae, on the other hand, are a little less glamorous, looking a lot like miniature slugs. Both feed on either the emerging spears or feathery foliage, weakening plants and with them the prospect of a harvest this season or next, or both.

The sensible solution, like for many pests, is to inspect plants regularly with a view to hand-picking any of the grubs or beetles you come across. Dispatch them once and for all by dropping them into a bucket of water to drown.

Asparagus beetles overwinter in grassy tussocks and old foliage, so cut back and remove dead plant matter at the end of the season and keep on top of the weeding.

2. Red Lily Beetle

Red lily beetles won’t bother your vegetables or fruits, but they’ll certainly seize any opportunity to ravage your lilies and fritillaries. These bright red and, it has to be said, beautiful beetles gnaw rounded holes in the leaves but will happily munch on petals and seedpods too.

The round, swollen reddish-brown larvae begin by rasping away on the undersides of leaves, causing dried brown patches, before they swell to even greedier proportions to take on whole leaves. Squeamish gardeners turn away now, and definitely don't look at the picture below...the grubs are typically covered, often completely obscured, by their own sticky black excrement. I know, gross right!?

Light damage is no great shakes, but extensive stripping of foliage will compromise the bulb below ground and the chances of flowers next year.

Scour plants from spring for both the beetles and their larvae. Pick off and dispose of any you find. If their numbers outpace your ability to cope there are organic pyrethrum-based sprays available. Infested container plants can be repotted at the end of the season into fresh potting mix, free of lurking overwintering adults.

3. Viburnum Beetle

The voracious viburnum beetle is a relentless feeder of, you guessed it, Viburnum species, including common garden staples like Viburnum tinus (laurustinus) and V. opulus (guelder rose). With a number of viburnums offering leafy cover in my garden, I dread the day this particular pest turns up. Most damage occurs in spring courtesy of the cream-coloured larvae, which have black markings. Apparently, they can pong a bit too!

Attacks are sudden and extensive, so hand picking’s out of the question for this ne’er-do-well. That’s the bad news. The good news is that even a severe attack leading to widespread defoliation is unlikely to affect the shrub’s long-term health.

You can spray the larvae as they feed in spring, again using an organic pyrethrum-based insecticide. Just be aware that while the spray may be organic, it doesn’t make it any less hazardous to many other bugs. Absolutely avoid spraying when your viburnum is in flower or you risk knocking out a host of pollinators too – collateral damage no one wants.

Seen One? Report it at BigBugHunt.com

If you’re in your garden checking for this unholy trinity, please take time to report any findings to The Big Bug Hunt, our bug tracking project. We aim to create a warning system to alert gardeners when pests are heading your way so you can take steps to prevent or control pests naturally and organically.

Phase one of the pest prediction service is already live and this season we’re working hard to refine the system using more of your reports. So if you see any of the beetles above, or indeed any other bugs, hop on over to www.BigBugHunt.com and tell us what you found.

Asparagus beetle image at top of the page ©Entomart

Plants Related to this Article

Asparagus Grow Guide

Lily Grow Guide

Bugs, Beneficial Insects and Plant Diseases

Asparagus Beetle Guide

Red Lily Beetle Guide