Citrus trees include grapefruit, oranges, lemons, kumquats and limes that — depending on the species — grow in U.S. Department of Agriculture plant hardiness zones 9 through 12. These fruit trees can come under attack from damaging diseases and insects, that can affect the fruit formation of your citrus. To kill, treat or prevent problems, oil sprays are just one choice.
Oil Sprays
Neem, jojoba and horticultural oil are a few of the oil sprays available. Plant-based oils — such as neem and jojoba — are made using oil extracted from various parts of certain plants. Made from highly refined petroleum, horticultural oil has been used for centuries to keep insects off plants. When applied properly, these oil sprays can control different pest or disease problems on citrus. Oil sprays degrade quickly with little to no residual effect on the surroundings.
Insects
Leafrollers, aphids, mealybugs, thrips, whiteflies, cutworms and scale insects are some of the insects that infest citrus plants. These insects cause varying levels of harm but typically will leave the citrus leaves wilted, curly, twisted and discolored. The damaged leaves can fall from your citrus tree prematurely. Aphids, mealybugs, thrips, whiteflies and scale insects feed on the juices inside the leaves by inserting a straw-like mouthpart to suck the liquid from the plant. Leafrollers eat leaves and ripe fruit and roll leaves up, securing them with a shiny thread. For the oil spray to efficiently control the insects, then the pest has to be entirely covered with the oil. To increase the efficacy of the oil, thoroughly cover the citrus plant — including the tops and undersides of their leaves — with the spray.
Diseases
Horticultural and neem oil control insects — for example aphids and whiteflies — that carry viruses that infect plants. In addition, they protect the citrus plant from various fungal diseases, such as powdery mildew, rusts, dark place and scab. Neem oil works by preventing the fungal spores from sticking to the plant while horticultural oil disrupts the fungal pathogen’s cell wall and also keeps it from attaching itself to the citrus plant. These oil sprays have a very low toxicity to people, birds and mammals but may cause skin irritation. They are toxic to fish, so don’t use them about ponds and be certain that there’s no runoff that may enter a body of water.
Application
No matter which oil spray you use, follow the manufacturer’s instructions printed on the tag. Most of these sprays cannot be applied when temperatures are greater than 90 degrees Fahrenheit. Higher temperatures can cause the oil to burn the citrus plant. Wait for a calm day to apply the oil spray to stop spray drifts and decide on a day when rain isn’t in the forecast for 24 to 48 hours. A second program seven to 14 days after you applied the first treatment may be necessary. The oil spray tag will have specific instructions for the kind and brand of oil spray you’re using.