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Chart of Pests on Leaves

by Nanette Londeree, Master Rosarian

Roses will begin their amazing transformation from spindly sticks to lush shrubs during the next couple of months. And that healthy, vibrant young foliage is just ripe for attack by a bunch of different pests. In its tender form it’s also susceptible to damage from non-living, or abiotic causes. Protecting your plants starts with keen observation – looking closely at the foliage for signs of damage, and figuring out what is causing it.

This issue we’ll be looking at sources of pest damage to the leaves of plants along with identifying some of the “good guys” you may find perched on your foliage. The table on the next page includes the name of the pest, what it looks like, the type of pest, the time of year you’re most likely to encounter it, major signs and symptoms (a sign is direct evidence of the cause of the injury, either the presence of the actual pest, or some part of it; a symptom is the change in appearance of the plant part) and where applicable, a photo or description of the damage done. For beneficial insects, there’s a list of their favored prey. The text in the chart is color-coded to further help your pest identification - red for the “bad guys” and green for the “good guys.” Pests that don’t do much damage and are mostly a nuisance are identified in blue text.

In this series, we’ll be discussing different types of pests – insects and mites, fungal, bacterial and viral diseases, and abiotic disorders. We are starting with insect pests that you might observe on rose leaves (though you may find them on other parts of the plant.) An aid to identifying insect pests is their feeding habit – whether they are a sucking insect, extracting vital nutrients from the plant, or a chewing pest that actually removes a portion of the plant part. Piercing and sucking insects, in general, damage plants by inserting their mouthparts into plant tissue and drawing out plant juices, causing stippled (spotted-looking), wilted, deformed, stunted or discolored plant parts. Many, like aphids, also secrete honeydew that in turn attracts ants and supports the growth of sooty mold. Some sucking pests can inject toxic materials or transmit disease organisms into the plant while feeding.

To effectively manage pests in the garden, remember to:

  • Know what a healthy plant looks like
  • Keep an open mind
  • Know your enemies
  • Take a real good look at the plant
  • Think about the history of the plant and its surroundings
  • Consider that it may be multiple problems
  • Look for patterns
  • Eliminate what it’s not
  • Double-check the obvious
  • Make a preliminary diagnosis

    Once you’ve made your tentative diagnosis, consult your other resources to find ways to manage the pest. Consider using the integrated pest management approach – decide on the level of damage you can tolerate then follow the progressive control approach beginning with the least toxic method, cultural, mechanical, biological and finally, chemical.

    Next issue, we’ll continue with what’s bugging your leaves with a focus on diseases and abiotic disorders.

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    Last Modified: 08/06/2013