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Plant Diseases/Help with meyer lemon tree


QUESTION: There are these egg like things all over my tree and the trunk has some blackish coloring. I noticed there were ants crawling all over the tree too. The white dust looking stuff in the pics is a seven dust I sprinkeled on it to hopefully help. Its not on the entire plant yet. Please help me identify and help my problem. Thank you

ANSWER: These are aphids and the ants are gathering residue form the aphids.
The effect of lichens on a tree are only slightly detrimental. The plants are epiphytes. That is they derive their nutrients from the air and not from the plant on which they are growing. Although they are not parasitized, literature reports suggest that lichens do have a slight negative effect. The main concern is that lichens give a tree an unkept appearance. Presence of lichens also is a good indicator of a thin tree canopy. This often leads homeowners to conclude that lichens are the cause and not the effect of thin foliage. The best control for lichens is maintain the tree in good condition. This will insure a dense canopy which will shade the limbs and reduce photosynthesis. Without photosynthesis, lichens are not able to manufacture food needed for growth and development.  

The abundance of lichens are a symptom that something else is causing the problem. The growth of the lichens means they are taking advantage of the sun light exposure caused by the thinning foliage.  

Several systemic insecticides are useful in aphid control. Aphids have sucking mouthparts and are thus very susceptible to pesticides located in the plant vascular system. Some of the systemic insecticides also have contact activity. Systemics injected or applied to the ground are less harmful to beneficial insects. Systemic insecticides include: acephate (Orthene).

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QUESTION: So what is causing these to attack my plant and any sugestions on what will get rid of them

Aphids like plants that are growing well. Aphids are a part of nature and are in low populations but if the weather conditions are right and the plant tissue is healthy the aphid population can grow. This is when treatment is needed for a plant. The way to get rid of them is to treat the plant with an insecticide. This will reduce the population to almost zero and will prevent damage to the plant. I hope this helps. There is nothing you are doing to cause the aphid population.

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Jim Hyland


30 years experiance in the ID and management of forest diseases and ID of landscape tree diseases.

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