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Hot on 3 June 2003
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Orange Rust of Brambles

By Gail Ruhl, Sr. Plant Disease Diagnostician, P&PDL, Purdue University

Orange rust is now appearing on blackberries and black raspberries in Indiana; it does not affect red raspberries. The orange rust fungus grows “systemically” throughout the roots, crown, and shoots of an infected plant, and is perennial inside the below-ground plant parts. Once a plant is infected by orange rust, it is infected for life and will produce spores every year after it is infected. The disease does not normally kill plants, but causes them to be so stunted and weakened that they produce little or no fruit.

It is important to identify orange rust at the appearance of abnormal growth of new canes in the spring because infected plants can be easily identified and removed at this time. Within a few weeks, the lower surface of infected leaves will be covered with blister-like pustules that are waxy at first, but soon turn powdery and bright orange. This bright orange, rusty appearance is what gives the disease its name. Rusted leaves wither and drop in late spring or early summer. Later in the season, the tips of infected young canes appear to have outgrown the fungus and may appear normal. At this point, infected plants are often difficult to identify. In reality, the plants are systemically infected, and in the following years infected canes will be bushy and spindly, and bear little or no fruit.

When diseased plants first appear in early spring, dig them out (including roots) and destroy them before pustules form, break open, and discharge the orange masses of spores. If plants are not removed, these spores will spread the disease to healthy plants. The removal must be complete - new infected plants will grow from small pieces of roots left in the ground. Orange rust is also widespread on wild blackberries and black raspberries in Indiana, thus it is important to not only remove infected plants from the blackberry planting but to also remove similar plants from wild areas nearby.

Fungicides with proven effectiveness against this disease have not been found therefore timely eradication of diseased plants is essential.

For more information, please see the following website: http://ohioline.osu.edu/hyg-fact/3000/3010.html


Orange Rust of Brambles Rust
pustules on underside of leaf

Photo by Bruce Bordelon,
Extension Specialist, Horticulture

Orange Rust of Brambles
Close-up of rust pustules

Photo by Steve Mayer,
Marion County CES

Sycamores Losing Leaves!

By Gail Ruhl, Sr. Plant Disease Diagnostician, P&PDL, Purdue University

Are there more sycamore leaves on your lawn than on your tree? Do not panic. Your sycamore tree is not dying, it is merely infected by the most common fungal disease on sycamores in Indiana. This fungal disease is favored by cool, wet, spring weather.

Symptoms: The most characteristic symptom appears as large irregular tan to brown necrotic areas that develop along leaf veins, sometimes expanding to the leaf margin, causing distortion of the leaf. Twig dieback, wilting and browning of newly emerging leaves frequently occur. Numerous cankers (localized, injured areas) occur on twigs and branches. Severely infected rees may lose many leaves, beginning at the bottom of the tree, and may appear more dead than alive.

Disease Cycle: The fungus, Apiognomonia veneta (anamorph: Discula platani), overwinters in infected leaves and branch and twig cankers. In spring, spores are produced and are spread by wind and splashing rain to newly emerging leaves, buds, shoots, and twigs when conditions are favorable. Spores are produced from newly infected tissue, allowing secondary infections to occur.

Management: Even during years of severe infection, sycamore anthracnose does not result in tree death. The most practical control is to fertilize defoliated trees to lessen the stress that comes from having to produce a second flush of leaves. Spraying is generally not warranted on large, or older established trees.

For more information, refer to BP-9, Anthracnose of Shade Trees located on the web at: http://www.agcom.purdue.edu/AgCom/Pubs/BP/BP_9_W.pdf (PDF 496K - Requires Adobe Acrobat to view and print).

You may also download http://www.hort.purdue.edu/ext/HO-140.pdf for fertilization recommendations.

Foliar symptoms
Stem canker and foliar symptoms


The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by the Purdue University Cooperative Extension Service is implied. Any person using products listed assumes full responsibility for their use in accordance with current direction of the manufacturer. Purdue University is an equal opportunity/equal access institution.

Information listed is valid only for the state of Indiana.

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