Pests & Diseases

Wool-sower gall

May 4 2017 RHR 107Some of the newly installed oaks on campus appear to have grown cotton balls with pink spots. These are actually a type of tree gall called Wool-sower gall.

This gall is produced by the harmless Cynipid gall wasp (Callirhytis seminator). photo credit: R. Robert

This gall is produced by the harmless Cynipid gall wasp (Callirhytis seminator). photo credit: R. Robert

This gall is produced by the harmless Cynipid gall wasp (Callirhytis seminator). These wasps lay their eggs on a specific plant and the eggs produce the grubs whose secretions cause the gall formation. The gall provides protection and nutrition. Their favorite host plants are oaks.

The galls do not harm the tree, …

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Cedar Quince Rust

April 21 2017 RHR 077This spring, orange goop appears to be taking over the Juniperus virginiana ‘Burkii’ in the BioStream. During damp springs, cedar quince rust (Gymnosporangium clavipes) produces cushion-shaped, orange, gelatinous blisters through the bark where the branches are swollen on cedars and junipers.

During damp springs, cedar quince rust (Gymnosporangium clavipes) produces cushion-shaped, orange, gelatinous blisters through the bark where the branches are swollen on cedars and junipers. photo credit: R. Robert

During damp springs, cedar quince rust (Gymnosporangium clavipes) produces cushion-shaped, orange, gelatinous blisters through the bark where the branches are swollen on cedars and junipers. photo credit: R. Robert

This fungus has a two-host lifecycle.  A few hours of wet, cool (74 to 78 degrees F) spring weather are sufficient for telial swelling on the …

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Oh No! My Cherry Trees are Brown

March 29 2017 RHR 016Cherry and magnolia trees are blooming throughout the Delaware Valley but you may be asking why your flowers are brown and not pink. Some early blooming cultivars of cherries and magnolias have succumbed to frost damage and turned brown.  As a result, they have no blooms this spring, just browned flowers.

Most of the Prunus 'Okame' blooms were destroyed by frost. photo credit: R. Robert

Most of the Prunus ‘Okame’ blooms were destroyed by frost. photo credit: R. Robert

No need to panic. Your tree is not dead. It is just a victim of unseasonably warm temperatures in February and then a return to cold temperatures in March. The warm temperatures caused early blooming …

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