Dormant Oil – To spray or not to spray

Why dormant oil? Our climate is conducive to many varieties of scale including Pinon Needle Scale, and scale on Sycamore, Plum, and Oak trees and euonymus shrubs. Aphids run amuck once things start to flower. Powdery mildew is unsightly on shrubs like euonymus, roses, lilac, and Photinia to name a few. Spider mites love our dry climate and love dense evergreens such as Pine trees and junipers.

Oils kill exposed insects such as scale, mites, and aphids by either suffocating them (covering up breathing tubes) or by directly penetrating the outside cuticle and destroying internal cells. Additionally, dormant oil will trap and kill fungal spores.

These are some of the advantages.

  1. Suffocates most species of mites and scales, including some activity on eggs.
  2. Minimal likelihood of insects or mites developing resistance.
  3. Less harmful to beneficial insects than other pesticides.
  4. Relatively safe to birds, humans, and other mammals.

These are some disadvantages.

  1. Potential plant damage if incorrect oil is used or used at improper rate during the growing season and
  2. Minimal residual activity to kill new pest infestations.

To sum things up, Dormant Oil is relatively safe to use and is an effective tool to maintain the health of your trees and shrubs. We at Baca’s Trees, often use dormant oil as a preventive measure for most trees and shrubs and we use it in conjunction with a water soluble fertilizer. The combination makes a great spring treatment for trees and shrubs while being environmentally friendly.

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