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Border Plant Bugs

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In recent weeks, Master Gardener hotlines and UC Cooperative Extension offices in the Central Sierra foothills have been bombarded with the question, “What is this bug? They’re all over my strawberries!” Samples have arrived in jars and bags, with the sample insects in “living and breathing” condition and also in a decidedly “squished” state.

The identification of all these various insects is the same. It is the bordered plant bug (Largus succinctus or Largus sp.) The adult is pretty easy to identify, but the immature nymphs can sometimes be a bit more difficult, as they don’t look anything like the adults. The nymphs (immature stage) lack fully developed wings. Their color is metallic blue/black with an orange, warning triangle at center.

Bordered plant bugs feed using piercing-sucking mouthparts and are classified as true bugs, order Heteroptera. As such, their food consists entirely of liquid extracted from plant tissues. Their feeding is concentrated on the most nutritious parts of plants such as flowers and fruit. In most cases no control is needed as the insects often move on late in the summer and don’t cause significant harm to ornamental plants. In the food garden, the insects can cause damage by scarring developing fruits, such as strawberries and blueberries. In this case, hand removal is easy by knocking insects into a mason jar, vacuuming them up using a shop vac, or stepping on them. No chemical control is recommended.
If you would like to read more about bordered plant bugs, see the UC Statewide Integrated Pest Management Program’s pest note on box elder bugs, Although not the same insect, they are similar and the biology and control are similar.