Citrus leaf miners are tiny moths that lay eggs on newly emerged citrus leaves.
When eggs hatch, the tiny larvae meander around in the leaf, leaving zig-zag trails. This causes the leaf to be misshapen or curl. The damage to the foliage does not kill trees, but it can stunt the growth of young citrus.
Late April is a good time to start treating for leaf miners.
The first flush of foliage is usually not damaged by the leaf miner so you might think everything is OK. However, every flush of new growth for the rest of the year is likely to be damaged by this insect unless you do something to prevent them.
Leaf miners are common. They were first reported in Florida in 1993 and are now widespread to all Gulf Coast states. In Florida, citrus leaf miners seem to have a constant life cycle. In Georgia, the winters may break up the continuation of the life cycles.
From the time the adult moth lays the egg to the time it turns into an adult moth is about three weeks. The moths lay a single egg on the underside of the leaf. The egg hatches in two to 10 days and burrows into the leaf. Populations peak in the summer and early fall.
The larvae are greenish-yellow and translucent. The vulnerable larvae stage may only last four to five days. With a life cycle this quick controlling them is difficult. One of the problems with controlling leaf miners is that the larvae are well protected from foliar sprays. The larvae migrate to the leaf margin and transform into a pupae, then a moth.
The white to silvery colored moths are tiny, about half an inch. They have black dots on the wingtips. Moths are rarely seen and only live for a few days. The moths are most active in the early evening or the early morning.
One option that may help reduce the incidence of the citrus leaf miner damage is the use of horticultural oils. As soon as new shoots develop, apply the oil. Oil will need to be reapplied every 10-14 days until the leaves harden off. You will need to repeat this with each new flush of growth.
Oils act as a barrier on the leaf so the egg will not stick to the leaf. Be careful to read the label and mix the oils with water as instructed. High temperatures and intense sunlight in combination with oils can cause leaf burns. Horticultural oils also help with control of aphids, scales and other insects that cause problems on citrus.
Systemic pesticides containing imidacloprid are usually more effective. Imidacloprid is absorbed into the plant tissue where the larvae are located. Products such as Bayer Advanced Fruit, Citrus, and Vegetable Insect Control contain imidacloprid.
When used as a drench, imidacloprid is absorbed by the roots into the tree. This may protect the foliage for up to two months. Imidacloprid can also be used as a foliar spray, but this may only protect new foliage for a couple of weeks. Avoid spraying during bloom time because it will kill bees.
Insecticide products that contain the natural insecticides azadirachtin or spinosad show some efficacy against larvae and are safe for natural enemies. However, the residues do not last long, and these insecticides might need to be reapplied every seven to 14 days.
Application of Green Light Spinosad is limited to six times per season. Parasitic wasps also help with their control so avoid random sprays with malathion, permethrin and carbaryl. Do not use products that are not labeled for citrus.
On younger trees (usually four years or less), citrus leaf miners can reduce growth and fruit production if infestations are great enough. Damage on older trees is usually not significant and treatment is usually not needed.
For more information on citrus leaf miners refer to the UGA publication: https://secure.caes.uga.edu/extension/publications/files/pdf/C%201145_6.PDF
Jake Price is University of Georgia extension agent/coordinator for Lowndes County. More information: Call (229) 333-5185, or email email@example.com.