Do you spray your roses?

Title: An In Vitro Study of Fungicide Effects on Pollen Germination and Tube Growth in Almond

Authors: Weiguang Yi, S. Edward Law, and Hazel Y. Wetzstein

Published in: HortScience, volumn 38, pages 1086-1088, (2003).

Abstract: "In almond [Prunis dulcis (Mill.) D.A. Webb.], fungicide sprays are required to prevent blossom blight, which can infect open flowers. Numerous studies have reported detrimental effects of agrochemical sprays on pollination, fruit set, and yield in tree fruit crops. However, effects of fungicides on pollen germination and growth in almond are little known, particularly those from recently developed active ingredients. In this study we evaluated the effects of commercial formulations of 10 fungicides on pollen germination and tube growth in almond using in vitro assays. Assays conducted at 1/100 recommended field rates (RFR) were effective in delineating differences in almond pollen sensitivity to different fungicides. Captan and azoxystrobin were the most inhibitory, with germination percentages of less than 1% of the no-fungicide control. Germination was not significantly affected by propiconazole and benomyl. Intermediate inhibitory effects on pollen germination were observed with ziram, cyprodinil, maneb, thiophanate-methyl, iprodione, and myclobutanil. In contrast to germination, tube growth was less affected by the presence of fungicide. In pollen that germinated, tube elongation was the same as in controls in five of 10 of the fungicides evaluated. Nonetheless, azoxystrobin and captan reduced tube elongation by

Yes, I do spray the plants, but usually begin after the primary pollination season. I don’t see a problem with the germination of pollen. I get reasonably good take with pollinations. A problem that I have noticed, though, is that since I began using Immunox (Myclobutanil) regularly the germination of my rose seeds has been very poor–rarely more than 15%, and usually less. I mentioned this problem this year in a post on this forum (see link below), but nobody responded to my question.

I don’t know whether people didn’t respond because they had no knowledge of a link between Immunox and reduced germination or because they were too busy. However, after the first spraying of the season, I decided to switch back to Funginex (now Rose Pride) since germination had been better when I was using it. I know that there are all sorts of variables that may enter into the problem, but if there is a major change in germination percentage this year (which was very poor for rose growing here), I’ll consider my question answered. I’ll let everyone know what I discover.


First of all I’m a rose hobbyist at this time in my life. I don’t consider myself a serious hybridizer. I don’t spray mainly out of concern for my health and the environment. I’ve noted that cancer seems to be prevalent in those that spray toxics. I’d prefer not to be a statistic.

Roses should be able to get along without spray as far as I’m concerned but then I live in a climate where disease is seldom a problem. I sympathize with those that live in more challenging areas in terms of disease and insect attack. I’m less worried about pollination and more concerned about health issues. Thanks, Robert

Yes but only with copper, suplur lime, zinc, etc type lines. Ive seen one too many people die from cancer and whether or not harsh chemicals were the cause, Id rather not find out and/or risk the safety of those visiting the garden.

I don’t use fungicides. I either remove disease-ridden roses, or let nature take care of them. I do, however, use cygon 2e against the larva of spittlebugs which causea damage to new growth. I spray selectively.

Many people are concerned about this issue and for good reason. I’ve recently started experimenting with less toxic alternatives for treating seeds, like H2O2, Neem Oil, Baking Soda etc. So far I don’t think I have anything definitive to report other than, 1) an initial 24 hour seed soak in H2O2 works better than a 5 minute soak, and 2) that I’ve lost a lot of seeds to fungus this year! It’s possible the 24 hour soak works well enough. I need to play around with another batch of seeds, as I didn’t keep records of length of soak when I started most of the seeds this year. Once the mold starts, it’s definitely harder to control, and H2O2 soaks seem to work some of the time and not other times.

It seems to me if we all played around with different natural methods, one of us will come up with a good alternative that stops the fungal growth and allows for good germination. I know that some here find fungus to be ok, but not me. Perhaps it’s the type I have. Looking at my seeds, I can see at least 4 different types that I can visually identify. One type of black fungus’ seem to be pretty deadly and one type of white seems very harmful to the developing root. And at least 1 type of white fungus seems not to be harmful at all to the developing seeds and germinated seedling.

How about it, guys? If we all do a little experimenting, I’m sure we can find some natural alternatives that allow us to breed roses without potentially hurting ourselves in the process! Anyone game or are you completely satisfied with the current methods you are using?

I think in the past I struck people as strange as I’ve said, I’m more comfortable spraying my fruit trees with spray than my roses. Even though the fruit trees product is ingested and the roses are not - here is my reasoning (such as it is):

I only spray the fruit trees around bloom time and shortly thereafter (I aim for useable fruit and am not that worried about cosmetics). It’s generally several months thereafter when I’m harvesting fruits (I don’t spray berries at all). And the fruit trees are generally fairly far removed from my house.

I’m in among the roses more often. I’m potentially harvesting (blooms) recently after spraying and potentially getting scratches from the thorns. And the roses are closer to my house.

I did attempt a modified Cambridge spray program this year. As long as I kept it up, the plants looked good. But with all the continual rain we had the year in the mid-Atlantic and a busy schedule, I evenually stopped, and lost a lot of leaves to blackspot. The question I don’t have the answer to is whether the leaves would have succumbed anyway with the rising temps, or the spray would have reduced the infection amount.

Chris Mauchline

SE PA, zone 6