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Search Results for ' Tomatoes--Diseases and pests'

PAL Questions: 3 - Garden Tools:

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Keywords: Verticillium, Tomatoes--Diseases and pests

PAL Question:

I was just outside checking on the slow ripening progress of my tomato plants and noticed something that has me concerned. There seems to be a fungus or mold at the very base of my "super fantastic" tomato plant. Other than this issue and the slow ripening the plant seems to be doing okay. I haven't noticed this fungus/mold before so I don't know if has just appeared and is spreading rapidly or if it has been there all along. Do you know what it is? Will it spread through the entire plant? Will it spread to the other tomato plants and veggies in this bed? Should I remove the entire plant?

View Answer:

This sounds a lot like Fusarium wilt, but it could also be Verticillium (another fungal problem) or even walnut toxicity (do you have any black walnut trees within 50 feet of your plants?). It might even be excessive watering which is causing the problem.

According to The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale, 1996), you can cut open a stem near the soil line and look for internal discoloration. Verticillium affects the whole plant, while Fusarium will start by infecting individual shoots and then spread. Tomato Fusarium only affects tomatoes, while there are numerous plants which are susceptible to Verticillium. The best thing to do if your plant is suffering from these fungal diseases is to destroy them, so you may want to take a sample to a Master Gardener Clinic for diagnosis before you do anything drastic.

General resources on tomato problems:

Recognizing Tomato Problems from Colorado State University Extension.

Vegetable MD Online from Cornell University.

University of California, Davis Integrated Pest Management has excellent pictures of the insides of the stems, for comparison.

Season All Season
Date 2007-07-25
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Keywords: Tomatoes--Care and maintenance, Lycopersicon, Tomatoes--Diseases and pests

PAL Question:

It's midsummer, and I have a bunch of healthy-looking green tomato plants without any fruit. Shortly after I planted the starts, the flowers developed, and promptly fell off, taking a bit of the stem-end with them. The spot where I've planted them is in full sun, they have good soil, and they get watered as they should. Any idea what might be going wrong?

View Answer:

The problem which most closely resembles your description of what is happening with your tomato plants (flowers falling off shortly after planting, and taking a bit of the stem as they drop) is called 'blossom drop.' According to D. G. Hessayon's Vegetable Expert (PBI, 1990), blossom drop occurs when pollination fails to take place, and there is dryness at the roots or in the air. There is no treatment for this malady, but watering regularly, spraying flowers in the morning, and tapping the plants to aid pollination are preventive measures. Attracting beneficial insects to your garden will also help with pollination.

Here are links to more information that may be useful to you:

  • University of California Integrated Pest Management pages on tomato problems and pollination
  • Washington State University - Spokane County Extension: Why Blossoms Fail. Note also that WSU Extension in Spokane County says cool night temperatures may cause blossom drop.
  • University of Illinois Extension: "Tomato blossom drop is very common with high summer temperatures. Tomatoes will drop blossoms when daytime temperatures in the summer are above 90 degrees F. Blossoms will also drop earlier in the growing season when night temperatures drop below 55 degrees F."
  • This article from about.com provides a lot of detail about the problem and how to prevent it:
    Blossom drop can be attributed to several causes, most often related to either temperature and/or stress.
    1. Temperature too high or too low
    2. Lack of pollination
    3. Nitrogen: too much or too little
    4. Humidity too high or low humidity
    5. Lack of water
    6. Stress from insect damage or disease
    7. Too heavy fruit set

    This article recommends planting varieties known to do well in your climate, ensuring pollination, avoiding over-fertilizing, taking note of humidity levels, and watering deeply once a week in dry weather.

Season All Season
Date 2009-08-05
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Keywords: Honeybees, Nicotiana, Tomatoes--Diseases and pests

PAL Question:

I am about to plant Nicotiana mutabilis seeds, and I wonder: if neonicotinoid insecticides are harmful to bees, is the pollen in Nicotiana also harmful? Also, is it a bad idea to plant Nicotiana near my tomatoes (could it spread tobacco mosaic virus)?

View Answer:

Although neonicotinoids are not currently implicated as a direct cause of Colony Collapse Disorder, the Xerces Society for Invertebrate Conservationís "Are Neonicotinoids Killing Bees?" says that "recent research suggests that neonicotinoids may make honey bees more susceptible to parasites and pathogens, including the intestinal parasite Nosema, which has been implicated as one causative factor in CCD." The brief summary of the full report on this issue is well worth reading.

I doubt whether the pollen or nectar of the ornamental plant Nicotiana has the same properties as a formulated systemic pesticide which contains a synthetic form of nicotine. For an example of the ingredients in a neonicotinoid pesticide, see this fact sheet for Imidacloprid from the National Pesticide Information Center. I found a scientific article ("The effects of nectar-nicotine on colony fitness of caged honeybees" by N. Singaravelan et al., in Journal of Chemical Ecology, January 2006) which says that the floral nectar of Nicotiana species and of Tilia cordata contains trace amounts of nicotine. The authors concluded that "results indicate that honeybees can cope with naturally occurring concentrations of nicotine, without notable mortality, even when consumed in large quantities for more than 3 weeks."

As for your other question, Nicotiana does sometimes get tobacco mosaic virus, though the National Garden Bureau says it seldom has much trouble from it. Still, it is probably a good idea to keep some distance between your Nicotiana and your tomatoes (and any other solanaceous plants, like potato, eggplant, pepper) just to be on the safe side, or at least be sure to change gloves and clean tools after handling the plants. The main method of transmission of tobacco mosaic virus is "mechanical," that is, by handling a plant with the virus and then handling plants that are susceptible to it.

Season All Season
Date 2013-03-30
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December 12 2014 11:33:49