Ornamental orange trees are those not generally grown for their fruit because of their sour or bitter taste. These ornamental trees are called sour oranges (Citrus aurantium) and grow in U.S. Department of Agriculture plant hardiness zones 9 through 11. The same pests that attack other orange trees will attack the ornamental orange.
Aphids, scales, mites, thrips and whiteflies are sap-sucking insects that feed on the cell content coursing through the ornamental orange tree’s leaves. They do this by inserting their slender mouthpart into the tender parts of the plant and sucking the liquid up. This feeding will leave the foliage wilted and discolored. The damaged leaves may fall from the branches prematurely. Thankfully, sap-sucking insects rarely cause severe damage and -- if the ornamental orange tree is healthy -- can be tolerated with no chemical control.
The Lepidoptera order of insects includes butterflies and moths, including their leaf-eating larvae. Citrus cutworm, citrus peelminer, leafminers, California orangedog and loopers are a few insects in the Lepidoptera order that attack orange trees. Citrus cutworms feed on leaves and young fruit while moving through the orange tree. Their moving and eating will result in more leaves and fruit being damaged even in small infestations. The larvae of peelminers chew tunnels through the surface of the fruit while leafminers create the same type of tunnels on leaves. California orangedog feasts on tender leaves and -- in large infestations -- can defoliate the ornamental orange tree, but typically won’t cause long-term damage. Young loopers feast on the edge of leaves while older larvae chew holes through the foliage. Both young and old larvae may eat orange blossoms and young fruit.
Snails, beetles and earwigs are a few other annoying insects you may find on your ornamental orange tree. Snails tend to feed on both ripe and unripe fruit as well as leaves and bark. Beetles -- such as the fuller rose beetle -- feed on the edges of leaves, causing notches and a ragged appearance on the foliage. Earwigs chew on various parts of the ornamental orange tree including leaves, buds, fruit and bark. Thankfully, earwigs infestations are rarely large enough to cause serious damage, and chemical control is generally not warranted.
Most sap-sucking insects can be controlled using horticultural oil, insecticidal soap or neem oil. For a more natural option, increase the amount of predatory insects in the area. Ladybugs, parasitic wasps, green lacewings and parasitic flies are a few predators that feed on aphids, scales and mealybugs. To control Lepidopterans, use Bacillus thuringiensis. This bacterium targets the larvae of moths and caterpillars, and won’t harm beneficial insects. Bacillus thuringiensis causes the larvae to stop feeding, and they die a few days after ingesting the bacterium. Snails can be deterred from feasting on the ornamental orange tree by wrapping copper banding around the tree trunk. When the snail tries to slither across the copper, it will receive an unpleasant electric shock. Another option for snail control is to add snail bait at the base of the tree.
- UC IPM Online: Citrus
- Purdue University Horticulture & Landscape Architecture: Sour Orange
- UC IPM Online: Citrus Cutworm
- UC IPM Online: Peelminer
- UC IPM Online: Citrus Leafminer
- UC IPM Online: California Orangedog
- UC IPM Online: Loopers
- UC IPM Online: Brown Garden Snail
- UC IPM Online: Invertebrate Damage to Leaves
- Arizona State University: Citrus Aurantium
- David De Lossy/Photodisc/Getty Images