What Is Wrong With My Valencia Orange?

Is your tree infested by ants?

Is the one limb or canopy area yellowing, there is a distinct blotchy mottling on leaf blades, the fruit is small and misshapen?

Do the leaves have large, ragged holes in them?

Are the leaves covered with small bumps?

Are there any translucent or white tunnels in leaves?

Most pest ants feed on the honeydew produced by sap-sucking pests like aphids, mealybugs, scale, and whiteflies. They protect and tend to these insects, fighting off natural predators and parasites. The subsequent increase in the number of honeydew-producing insects then leads to exacerbated growth of sooty mold fungus. Ant control is often necessary to reduce the number of honeydew producers. Removing branches within 12-30 inches of the ground and applying sticky materials to the trunk can prevent ants from climbing into the canopy. Avoid using oil-based sticky materials, which can cause phytotoxicity.

Huanglongbing is a bacterial disease transmitted by Asian citrus psyllid. Control strategies should focus on populations of the insect vectors, reducing inoculum, and planting trees in conditions unfavorable to the spread of the pathogen. Monitor regularly for Asian citrus psyllid damage and treat as needed. Note that contact insecticides typically do not control all life stages and tend to show better efficacy against one stage over another.

Large, ragged holes in the leaves are caused by slugs and snails. Slugs and snails feed on the plant leaves usually at night. To control slugs and snails use diatomaceous earth around your plants. You can also handpick them during the night or use shallow dishes filled with beer as a trap.

Leaves covered by small bumps are caused by scales. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

Wandering, white or translucent tunnels in leaves are caused by citrus leafminers. Leafminers prefer young, tender foliage and cannot tunnel in hardened leaves. Avoid applying nitrogen fertilizer while populations are high, or the new growth will be severely damaged. As pruning too frequently can also stimulate new flush growth, avoid pruning live branches more than once a year, so that cycles of flush growth are uniform and short. Do not prune off leaves that have been mined—the undamaged areas of the leaf are still able to produce food for the tree.

Small animals like ground squirrels, pocket gophers, and rats may be attracted to fruits. Regularly remove fallen fruit and other plant debris to make the area less attractive to small animals. Depending on the pest you can erect barriers or place underground fencing to protect your plants.