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Chart of Pests on Flowers, Stems and Leaves

by Nanette Londeree, Master Rosarian

It’s all about timing – whether the punch line to a great joke, adding ingredients to your soufflé recipe so it doesn’t flop or asking your boss for a raise, timing can often determine whether your actions are successful or not. And it applies to the garden as well; you can prevent or lessen the impact of problem pests in the garden by anticipating them and timing your actions appropriately.

The study of recurring plant and animal life cycles – the leafing and flowering of plants, maturation of crops, emergence of insects, and the migration of birds is known as phenology and is based on the timing of biological activities. It is nature’s calendar - when the first daffodils bloom, robins build their nests, or leaves turn colors in the fall. Seasonality, like the dates of the first and last frosts of the year and the beginning and end of our rainy or dry cycles, are abiotic events that can influence the timing of nature’s recurring cyclical events.

The term phenology - derived from the Greek words phainos, meaning “to appear, to come into view” and logos, meaning “to study,” was first introduced in 1853 by the Belgian botanist Charles Morren. The practice of studying natures’ cycles has been going on throughout human history - our ancestors used the knowledge of animal behavior and plant growth and their associated timing for their hunting and gathering; developing agrarian societies collected seeds and learned to maximize crop production by optimizing the timing of planting and harvesting. And the Royal Court of Kyoto in Japan has observed and documented the flowering of cherry trees since 705 A.D!

The life cycle events, or phenophases, of flowering plants include leaf budburst, first flower, last flower, first ripe fruit, and leaf drop, while for insects it may include mating, egg-laying, larval development, molting or metamorphosis. Many of these natural events are simple to observe. And, whether consciously or not, you’re already actively practicing phenology by simply looking at your roses on a regular basis, and mentally recording what you see and when you see things occur. You can broaden your pest management opportunities by knowing who the bad actors in the garden are and when they’re most likely to appear, allowing you to take steps to proactively manage them when they are the most vulnerable to treatment.

The table below highlights the most common rose insect pests in our mild winter climate, and the months of the year when they are generally the most active, though the timing of activity may change year to year due to weather conditions or your specific locale. So, what’s bugging your flowers, stems and leaves this time of year?

Disease Calendar

Photo of deer courtesy of Diane Luboff
All other photos courtesy of Baldo Villegas’ website at

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Last Modified: 08/06/2013