The use of organic neem oil to deter or control pests have been documented for the past two decades (1). It is still popular today, particularly with those who wish to avoid chemical pesticides. Those of us who grow plants for competitive exhibition will also use neem oil as a natural leaf polish. I have successfully used organic neem oil on almost every genera in my collection without incurring any foliar damage, including African Violets, Alocasias, Anthuriums, Begonias, Calatheas, Philodendrons, and many others. To effectively neem plants, one will need dish soap (here, I am using Dawn), a spray bottle, organic/natural neem oil (may need to be warmed up if it solidifies), an electric fan, and a plastic pipette (or some may prefer a teaspoon). A big pot to heat water may be needed to warm the solution in the spray bottle.
A couple points for neeming success: 1) the foliage must dry quickly, preferably within the hour, with the help of an electric fan and 2) the solution containing the neem oil and detergent must be at least 90-100°F (32 -38°C). Avoid spraying at night and any remaining stagnant solution on the leaves can invite/favor fungal infections and/or result in foliage damage (left leaf). It has been documented that after cold water is suddenly introduced to foliage, it leads to cellular collapse, resulting in leaf damage (right leaf, 2). Below are the directions for properly neeming your plants with a quart (32 fl oz/946 mL) spray bottle (adjust volumes as necessary if you’re making less, making as much as you think you will need):
- Either fill a quart spray bottle with 90-100°F (32 -38°C) water or boil a pot of water to 100°F (38°C) and place a water-filled spray bottle into the warm water bath for 5 minutes
- Add 1.5 tsp (7.5 mL) neem oil and 0.5 tsp (2.5 mL) dishwashing soap
- Replace spray head and set to the finest mist setting
- Shake bottle vigorously and spray ~12 in (~30 cm) from the plant, making sure to cover top, bottom, and in the center of plant if it’s bushy
- Repeat step #4, remembering to shake the bottle frequently, until all plants are completed
- Unscrew spray cap so bottle does not contract as temperature cools. It is best to use the entire neem solution but if there is any left, it can be stored up to about ~week in a cool dark corner, and heated in a water bath before being used again
- Place all treated plants in a central area and turn on the electric fan, placed ~2-3 ft (~60-90 cm) away to mimic a soft gentle breeze flowing through the leaves. For a large area of treated plants, the fan may need to be moved around to ensure all plants dry quickly, preferably within an hour
- Thoroughly check all the leaves on all the plants, ensuring they are completely dried, and if so, place back under the light stand or by the window where it’ll remain
NOTE: this protocol is for organic pure neem oil, NOT extracted/concentrated/purified azadirachtin such as AzaMax or Azera.
