Hasaki

I'm posting this here to ask if any keeping Q. robur[English oak] or Q. garryana[Oregon white oak] as bonsai will see it and if they have found it on their trees.
This has become a problem on one of my Q. robur over the past two years and they[oak leaf aphids] have been found on another tree last year. I'm going to use a horticultural oil this spring as soaps have not worked.
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English oak (Quercus robur), both the regular and pyramidal variety, is affected by an insect called the Oak Leaf Phylloxera (Phylloxera sp., Phyllox-eridae). The key to recognizing this pest is to follow the progression of symptoms from spring to fall. Apparently, the insect overwinters on English oak in the egg stage, which are laid in bark crevices. The eggs should hatch near the time of leaf emergence. The nymphs walk to the leaves and start sucking sap from the lower side of the leaf. The insect is yellow and oval with a maximum size of approximately 2 mm. They often start sucking at the leaf edge and cause a very characteristic leaf roll. Each Phylloxera feeding site will result in a yellow spot showing on the upper side of the leaf. This damaged tissue will remain yellow for a period of time and then die, turning brown.
Left unchecked the whole leaf will turn brown and die, branches become defoliated.

Hasaki

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