Yellow and Black Bugs

• If you see small yellow and black bugs on your geranium, whether indoors or out, you likely have aphids. Aphids are tiny soft-bodied insects that occur both winged and wingless. They drink the sap out of plants by piercing the stems and leaves with sharp mouthparts and sucking. For this reason, they are termed "sucking pests." Aphids occur in a number of colors besides black and yellow, including green, red and brown.
  
  

Diagnostics

• One sure sign that you have an aphid problem is the presence of honeydew, and/or black sooty mold. The aphids' bodies are unable to process the large amounts of sugar in the plant sap, and so they excrete the excess in the form of a clear, sticky fluid. This fluid, or honeydew, can quickly coat the plant and drip onto the surrounding surfaces. The honeydew in itself is harmless; however, its propensity to harbor black sooty mold can interfere with the plant's ability to absorb sunlight if the mold is left unchecked.
  
  

Control

• Aphids can be controlled and even eliminated with commercially available insecticides. Horticultural oils sprayed on the plant are often successful, and more organic than chemicals. The oils coat the aphids and suffocate them. Bio-control is also an option, as many insects are predators of the aphids, the most notable being the lady beetle.
  
  

Timing

• Successful control of aphids is all in the timing. Check plants frequently for aphid signs, especially in the growing phase and before temperatures become very hot, as this is the time aphids are most prevalent. Aphids are much easier to manage and even eliminate if caught early. Large infestations can be much more problematic.