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Vijai Pandian column: Cosmetic disorders on landscape trees

Jun. 6, 2014
 
These galls are caused by a fungal disease called cedar apple rust, which infects junipers and rosaceous plants like hawthorn, crab apple and flowering quince.
These galls are caused by a fungal disease called cedar apple rust, which infects junipers and rosaceous plants like hawthorn, crab apple and flowering quince. / Submitted
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This strange phenomenon of young ash leaf drop is a common occurrence in spring, where the cool, wet weather triggers a fungal disease called anthracnose. / Submitted
The tiny red bumps or gall-like growths on maple leaves are maple bladder galls and are caused by tiny foliar-feeding insects called mites. / Submitted

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As the trees and shrubs completely leafed out and were doused with rain showers last week, the lush green landscape has also triggered some strange-looking disorders rousing many homeowners’ and gardeners’ curiosity.

Alien tentacle on junipers

In a relatively overnight period, the branches of many ornamental junipers are covered with an orange slimy mass that looks like alien tentacles. This distinctive gelatinous mass encircles a brown gall that clings on a branch of the juniper. These galls are caused by a fungal disease called cedar apple rust, which infects junipers and rosaceous plants like hawthorn, crab apple and flowering quince. However, on rosaceous plants, the symptom looks different by forming yellowish-orange circular spots on the upper surface of the leaves and a hairy fringe appearance on its underside.

The good thing about cedar apple rust disease is that it is a cosmetic disease and will not have a serious effect on the juniper’s health. In a couple of weeks, the gelatinous mass will dry out and become unnoticeable in the landscape.

Sudden ash leaf drop

Premature dropping of ash leaves worries many homeowners with fear of losing their valuable tree. This strange phenomenon of young ash leaf drop is a common occurrence in spring, where the cool, wet weather triggers a fungal disease called anthracnose. Around the mid-vein of the leaves, the infection of anthracnose causes a black-brown blotch that curls the leaves and ultimately causes them to defoliate. Strangely enough, this disease is cosmetic in nature and will not have an ill effect on the tree’s health. The ash tree will produce a second flush of new leaves as the season progresses.

Red pimples on maples

The tiny red bumps or gall-like growths on maple leaves are maple bladder galls and are caused by tiny foliar-feeding insects called mites. The pouch-like galls are initially red in color, but as the season progresses they turn green and eventually black. Inside the gall, the insect continues to feed, mature and lay eggs. Sometimes these galls can cause deformed leaves that can drop early. Once formed, the galls cannot be removed from the leaves. This disorder is again cosmetic in nature, and it is unlikely that the tree will experience injury or a decline in health or vigor. No control treatment is necessary.

Vijai Pandian is horticultural agent/educator for Brown County University of Wisconsin-Extension.

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