A Miner Problem

The first call of the morning today was a request to bring in a leaf for a diagnosis of a disease on a citrus tree. I asked the caller what the situation was and they said that their citrus trees had what their neighbor called “Minor Disease”. They went on to explain how the new leaves of their citrus trees were curling and disfigured. I suggested that they send me some pictures of the problem first. Below is what I received from them:

Leafminer damage on citrus leaves (red arrows point to leafminer galleries). 

Citrus leaf miner (which is an insect and not a disease) affects the new growth of citrus. Control is mostly cultural. Avoid pruning citrus at all more than once a year. Do not feed citrus in the summer of fall, when leafminer is most active, instead feed your trees in the late winter or early spring. Feed mature trees only once a year ½ of what the label says. By keeping new growth to a minimum you can control the leaf minor because it only infests new leaf growth. Eventually over time natural predators will effect some control over the leaf miner, and it will become a low level pest on your trees.

If your citrus tree is young and just establishing levels of leafminer damage can be quite dramatic. You can remove the disfigured leaves, although doing so can harm the growth of the tree if the removal is extensive. If your tree is a sapling however, you need to control the leaf miner without removing the leaves as doing so could stunt the young tree’s growth. You could monitor for the flying moth that lays the leafminer eggs on your trees leaves and spray either Neem oil or a Spinosad containing insecticide on the leaves when the moths show up in a trap (a trap specific for citrus leafminer) . You can purchase these traps at your local full service garden center or, order them online.

UC Davis page on Integrated Pest Management of citrus leaf miner

Mentioned above (these are examples and are not recommendations)

Traps 1 2 3

Spinosad product examples 1 2

Neem oil product examples 1 2

Fall Color Still Peaking

Here at the Arboretum we have a fall color season. It's not a punctuated, Rose Parade season like the east coast or the Sierras gets where all the trees that turn color do so in a blazing display of overwhelming reds, oranges, yellows and hot pinks (the color of dogwoods when they turn), instead ours is a lazy, slow moving parade put together by the local chamber of commerce where one float after another slowly rolls by, separated by marching bands blooming trees and aloes. 

Crepe myrtle tree with red fall foliage. 

Yellow fall foliage on these Crepe myrtles. 

Wisteria vine turning color as it drapes over bamboo plants. 

California native grapevine; a brilliant red performer in the fall as it drapes over 60 foot tall palms. 

Various fall color trees in the Meadowbrook section. 

Ginkgo biloba 'Canopy'

Carpet of spent leaves under Ginkgo biloba 'Canopy'

Ginkgo biloba 'Saratoga' in the herb garden. 

Ginkgo biloba 'Cleveland'

Chinaberry tree in the foreground, Ginkgo biloba 'Cleveland' in the background.

Formosan Sweet Gum, Liquidambar taiwanensis