What is this stink bug that is quietly evolving in the middle of your vegetable garden? This somewhat Stendhalian insect with its red and black coat is easy to spot. More prosaically, is the harlequin bug a danger for garden crops?

Life habits of the harlequin bug

Harlequin bug (Graphosoma lineatum) is part of the family of Pentatomidae. Seen from above, it has a pentagon-shaped body, hence the name Pentatomidae. This fingernail-sized insect sports alternating red and black stripes on the back. On the belly, it has black and red dots. Its head is triangular and its eyes prominent. It is very recognizable and therefore cannot be confused with another species of insect.

What are the damage of the harlequin bug in the garden?

Except in the event of an invasion, the harlequin bug don’t cause no significant damage in crops. This vegetarian flying insect feeds by sucking sap and parasitizes ripening green seeds. In the vegetable garden, the harlequin plant bug feeds mainly on carrot, fennel, angelica and dill. She pricks the still green apples, which can be “the cause of deformation at maturity”as explained by Claude Bureaux, gardening specialist for France Info. In nature, we can find the Graphosoma lineatum on apacies such as hogweed and others umbelliferous. Moreover, when it feels threatened, its lateral glands emit a substance with a very unpleasant smell.


Keep Harlequin Stink Bug Away

The harlequin bug does not like the smell of garlic. To naturally ward off bedbugs and insects in general, simply use crushed garlic (or powder) mixed with water, nettle manure or black soap diluted with water. These three ecological repellent mixtures can be used as a spray. However, their remanence is weak and it will therefore be necessary to repeat the operation several times.

The use of a pyrethrum insecticide is strictly discouraged, because it kills all insects without distinction, even auxiliaries such as bees. In general, do not use an insecticide, except in extreme cases of infestation.

harlequin bug
Credit: Lenti Hill/iStock

Harlequin stink bug natural predators

The website insect-net indicates that insectivorous predators such as birds carefully avoid tasting this bug, because “the red and black coloration suggests a menu for them that is tasteless in its pungency, and sometimes even downright toxic. The juxtaposition of black and yellow arouses the same distrust, because these colors recall the livery of biting insects (wasps and hornets in particular), and therefore the notion of danger.Stink bugs often have very bright colors to signal to predators or anyone who disturbs them that they are poisonous. Indeed, potential predators are wary of intense colors, as they generally signify the inedible character of an insect. As a result, she knows only a few predators.

The association between bright colors and toxicity is calledaposematism. This scientific term refers to the signaling mechanisms that an insect sends to its predators. The inedibility warning can be audible, chemical or visual.

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