Help! My Tomatoes Have Acne!
Your garden began with such promise. Its first fruits and vegetables were wonderful, almost miraculous. But as the growing season waned, your tomatoes did too.
They began to develop the oddest skin conditions-- dry patches, scars, yellow spots, black spots and unsightly cracks.
Dry, Unsightly Patches
Sometimes, especially at the height of summer when it's particularly hot and dry, tomatoes can get a nasty sunburn which often becomes infected. The burn manifests itself as dry, leathery patches called sunscald.
So long as sunscalded tomatoes haven't succumbed to rot, they can still be eaten. Just cut out the rough patch and enjoy!
How to Prevent Sunscald
To protect tomato fruit from sunscald, avoid pinching back leaves in midseason and use screens or row covers to provide shade.
5-Star Tomato Fertilizers
Deep, Deforming Scars
If your tomatoes have deep, deforming scars and holes on the bottom (the blossom end) they're catfaced. Although catfacing isn't particularly pretty, it doesn't adversely affect the nutritional value or taste of the fruit, and catfaced tomatoes are perfectly safe to eat. Catfacing is caused by things that happened in the environment (abiotic factors) when your plants were forming blossoms. It is not caused by disease or other biotic factors.
Possible causes include temperatures at under 58 degrees F, high levels of nitrogen in the soil and exposure to growth-regulating herbicides. Extreme heat and drought as well as unusually cool, wet periods during blossom time can also cause catfacing.
How to Prevent Catfacing
- Set your tomato plants out after dangerously low temperatures are no longer a threat. Although you may be itching to start your garden early, transplanting your tomato seedlings before it's time could expose them to the low nightly temperatures that cause catfacing.
- Buy fertilizer specifically formulated for tomatoes, or opt for rich, organic matter such as dessicated horse manure. All fertilizers are not alike. The high nitrogen fertilizers that you apply to your lawn or your orchid plants are inappropriate for tomatoes. (The first number on the fertilizer bag indicates its nitrogen content.)
- If possible, plant your tomatoes away from areas where they might be exposed to a 2,4-D herbicide. These weed killers are often sprayed along roadways. Like Agent Orange, they destroy plants by disrupting their growth cycle, and they'll interfere with your tomato plant's ability to set normal fruit.
- Select tomato varieties that are resistant to the catfacing, such as Floradade. Large varieties, such as beef steak, tend to be more susceptible.
Mild (But Effective) Insecticidal Oil
Yellow Spots & Rings
The tomato spotted wilt virus (TSWV) used to be a problem that primarily affected commercial tomato growers, but now home gardeners are frequently plagued by TSWV.
TSWV is carried by an insect, the western flower thrip. It first manifests itself as black spots on the tomato plant's stems and leaves. These eventually turn into cankers. Sometimes dark streaks also develop on stems. The plant's growth is stunted, and its fruit develops yellow spots and rings.
How to Prevent TSWV
- Discard infected plants immediately to control the spread of the virus to your other tomato plants.
- Keep your tomato patch weed-free. Weeds attract insects, including thrips.
- Buy tomato plant varieties that are TSWV resistant: Crista, Amelia VR (HMX 0800), Southern Star (BHN 444) and BHN 640.
- Thrips are famously difficult to control; however, you may be able to reduce the thrip population in your garden by applying insecticidal soaps, oils and/or powders as directed by the manufacturer.
Irrigation for the Home Garden
If your tomatoes are split by cracks that circle the stem (concentric cracks) or that spike outward from the stem (radial cracks), it's probably due to the weather. Growth cracks occur during rapid growth, usually when the fruit is close to maturity. Several factors --some within your control--may cause them:
- a period of dry weather followed by wet weather,
- excessive de-leafing of tomato plants coupled with fluctuations in temperature,
- soil high in nitrogen and low in potassium,
- irregular watering and
- excessive watering.
Once you notice that a tomato is cracked, pick it. If you leave it on the vine, it's likely to fall prey to disease.
How to Prevent Cracking
Want fewer cracked tomatoes? Try these three things:
- Apply tomato-appropriate fertilizer (see above), following the manufacturer's directions.
- Don't pinch off too many leaves! Doing so will expose your fruit to excessive heat and cold.
- Water at regular intervals, and consider using a drip-irrigation system. Once in place, they're easy to use, highly efficient and water-saving. And they're now available for container gardens, raised beds and traditional vegetable patches.
Blackheads & Whiteheads
When stink bugs feed on your tomatoes, they cause damage. Usually, it's minor. On green tomatoes, stink bug damage looks like tiny black spots. As the fruit ripens, the spots sometimes turn yellow. The tissue underneath the spots is spongy and white. If the damage is severe, it may even have holes in it.
Stink bug damage shouldn't prevent you from eating your tomatoes, however. Just cut out and discard the spongy bits.
How to Prevent Stink Bug Damage
- Keep your garden weed-free to reduce the stink bug population. Stink bugs overwinter in weedy areas.
- Remove stink bugs from your tomato plants. You probably won't want to do this by hand (they give off a nasty odor when handled). But you could use a bug vacuum.
Although stink bugs can be pests, some are extremely beneficial to your garden, eating canker-worms, gypsy moth caterpillars and other caterpillars—pests that really cause damage.
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