Two-spotted Spider Mites have developed quickly on hardy mums. Look on the underside of the oldest leaves along the midveins, for the mites, their eggs and white empty eggshells. You may see faint stippling, or chlorotic growth that resembles a nitrogen deficiency. During severe outbreaks, webbing can be seen after watering the crop.
If mite populations are detected early, Akari, Hexygon, Ovation, Sanmite or TetraSan may be options, for they tend to work best early in an infestation. If a quicker knockdown is needed, Floramite SC (be sure to correct the pH of the spray solution with Phase 5 or another product), Pylon, or Avid may be options.