Lemon trees can be plagued by a number of insects. While not as serious as lemon tree diseases, lemon tree pests can impact the number and quality of your lemon fruit. Learn to recognize signs of lemon pests and take action to keep your tree healthy.
An aphid infestation is easy to spot. These insects produce a sticky substance called honeydew--leaves appear to be dripping sap when they have honeydew. Honeydew attracts ants, so lemon trees that appear to have an ant problem likely have aphids. While a small number of aphids should not be a cause for concern, if these pests multiply they can seriously harm the lemon tree by causing the leaves to fall and branches to die back. Spray the lemon tree with insecticidal soap to remove the aphids. Gardeners may need to apply several doses to remove the entire aphid infestation.
A small, orange-colored insect that attacks lemon and orange leaves and fruit, the citrus thrip can damage lemon fruit. Gardeners should watch for lemon leaves that turn silvery-gray or curl inward and fruits that display silver coloring. Citrus thrips become rapidly immune to chemical control. Spray affected trees with insect sprays that contain spinosad, which is an organic compound. Gardeners should repeat treatment every two to three weeks.
Citrus Red Mite
Found most often on grapefruit and lemon trees, the citrus red mite is bright-red to scarlet in color and 1/50 inch long. The mites feed on citrus leaves, twigs and immature fruits. Fruit quality is not affected, but a high population of citrus red mite can cause the fruit to fall, and twigs and branches to die back. Like the citrus thrips, citrus red mites leave a silvery trail on fruits.
To control citrus red mites, spray lemon trees with a copper or sulfur-based miticide. Some sprays that curb citrus red mite also eliminate citrus rust mite populations. Organic growers can introduce insects that prey on the citrus red mite, such as lady beetles, aphid lions, tan mites or shiny button mites.
Citrus Rust Mite/Silver Mite
Known as citrus rust mites on orange trees and silver mites on lemon trees, these pests are too small to be seen without a magnifying lens. Silver mites feed on developing fruits, leaving a trail of silvery streaks. Warm or humid conditions can encourage mite infestation.
Gardeners should treat lemon trees for silver mites by using one of several approved insecticides that contain petroleum oil or by using wettable sulfur. Do not apply wettable sulfur in temperatures over 90 F or in heavy fog. Gardeners must wait at least 30 days to apply a sulfur treatment if an oil-based treatment has already been used, or vice versa.