Answer: Horticultural oil is extremely refined oil, suitable for use on outdoor plants to smother scale insects and insect eggs that are on branches and stems. It is sometimes called dormant oil. An even lighter weight oil, called superior oil or summer oil, is sold for summertime use. It's an important distinction because a heavy application of oil when temperatures are high could cause burning of plant tissues. These refined oils can be from petroleum or from plant oils, depending upon the manufacturer.<br><br>Cooking oil can be substitued for dormant oil. Simply mix one cup of vegetable oil with 1 tablespoon of liquid soap. Mix 10 teaspoons into a quart of water and your spray is ready to go. Try to apply when air temperature is above 40F and below 85F degrees.
Q&A Library Searching Tips