Not Fungus; Bugs!

What to look for to detect the four-lined plant bug.

This week’s garden tip was submitted by Wally Schmidtke, sales manager at .

Many of our customers have brought in plants covered with ugly, purple spots. The spots look similar to fungal disease spots, and can be misidentified as such.

The damage is inflicted by the four-lined plant bug, also known as “little thugs.”


Poecilocapus lineatus is easily identified by the four black strips running down its back. The little thugs have a wide range of hosts including fruits, vegetables, flowers, herbs and cucurbits.

With piercing-sucking mouthparts, the four-lined plant bug removes the plant's chlorophyll, leaving a window of upper and lower epidermis. A toxin present in their saliva is also secreted during feeding that digests the components responsible for holding the plant cells together.

This feeding produces white, dark, or translucent spots one-sixteenth to one-eighth-inches in diameter on the plant's leaves, which can merge together, if there is substantial damage, forming large blotches. Entire leaves can turn brown, curl up and eventually fall off.

Organic Treatments:

  • Dr. Earth Pro-Active Home and Garden Insect Spray
  • Bon-Neem Insecticidal Soap By Bonide
  • Japanese Beetle Killer RTU by Bonide

Conventional Controls:

  • Eight Insect Control by Bonide
  • Triazicide Insect Killer Once and Done by Spectracide
  • Systemic Insect Control by Bonide
  • Beetle Killer by Bonide

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