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Tomato Fruit Problems

Anne K Moore
Photographs Anne K Moore

You have probably read about tomato blossom end rot, a black sunken area opposite the stem end, caused by a “sometimes”-watering schedule as the tomato fruit is forming.  Other disease and insect problems can be just as ruinous to your tomato fruit.

Tomato fruit worms show up as holes on the surface of the tomato, or, as in the photograph, as a large hole next to the stem where they burrow into the fruit.  If you do not catch them in time and remove them, they will hollow out the tomato.  Hand pick and destroy the worms if you see them on the plant or fruit.  These worms also attack sweet corn ears.  Do not plant corn near your tomatoes.

Tomatoes can be sunburned just as we can.  Called sunscald, it shows up first as a large whitish area on the exposed part of the fruit.  The plants need at least six hours of sun a day, but tomato fruit needs the shade provided by the leaves of the plant.  Grow healthy plants by providing adequate water and low nitrogen fertilizer so that the vines will develop healthy leaves to protect the fruit. 

Anthracnose is a fungal disease that hits the tomato plant and fruit.  On the fruit, it appears as small, sunken, dark spots.  If you harvest them quickly and use them right away, all you have to do is cut out the infected spots.  If left on the plant (or windowsill) the spots will grow and the fruit will rot.  If the fungal disease is severe, you can combat it with fungal spray labeled for tomatoes or pull up and dispose of the vines.  Grow varieties resistant to anthracnose.

Hornworms chew large holes in the fruit, which appear as sunken brown calloused areas.  Just hand pick these large, squishy caterpillars and dispose of them.  I am too squeamish to do this, even with gloves, so I leave their disposal to my husband.  Just thinking about handling them gives me shivers.

The weather and the gardener cause cracks in the fruit.  A long dry spell followed by good soaking causes the fruit to swell and the skin to split.  These openings can let in disease, making the fruit susceptible to rot.  So, if the rains don’t come, the tomatoes need you to give them water.  Keep the soil mulched and moist.

Pinworms cause small Holes and black tunnels in the fruit.  Destroy the fruit in order to get rid of the pest.

Stink bugs feed on the green fruit, causing those yellow spots with white, firm flesh underneath on the ripe fruit.  Stinkbugs are hard to control.  You do not want to hand pick these pests.  Their name says it all.  Cut out the tough white area when serving the fruit.  Kill the stinkbugs with insecticidal soap spray or repel them with garlic spray.

Slimy visitors, like slugs and snails, also have a taste for tomatoes.  You can tell if they have been munching by the slime trail they leave behind.  Either ring the plants with copper tape made to discourage these nighttime visitors, or trap them by supplying hiding places during the day.  Melon shell domes make good traps.  During the day, upturn the shells, capture, and dispose of the slimy creatures in a bucket of soapy water.

Even welcome garden visitors can cause some damage.  Birds do more good than damage to most gardens, eating insects by the hundreds.  They can also be a nuisance if they decide to taste tomato fruit.  Small peck holes will soon rot.  You can harvest the tomato and use it quickly before rot sets in.  I have found that filled birdbaths, both on the ground and on pillars, are a huge help in keeping birds and even squirrels from sampling tomatoes.  Both may just be thirsty.

I like box turtles, which is my guess for the damage to this partly ripe tomato shown here.  This is a good reason to either plant extras for your garden dwellers or cage the plants so that the fruit is not on the ground.  Caged tomatoes in this garden with fruit high off the ground were not touched, ruling out opossums, raccoons, and squirrels, all of which are good climbers and tend to take their food to a safe spot.  This tomato on the ground was eaten on the vine.  It could also have been a family of field mice, but my money is on the turtle.

To try to keep unwelcome critters from visiting your tomatoes, you can fashion scare devices with aluminum strips or pie plates, or inflated owls on posts.  However, you do need to move any of these every few days or the thieves learn they are not a threat.

A few things to remember about tomatoes: 

  • Many heirlooms are more susceptible to most diseases.  
  • Heirlooms have more intense flavor than many of the new varieties but they will seldom set as much fruit.
  • Weeds can harbor pests.  Keep the vegetable garden weed free.
  • If you grow tomatoes in containers, every year before you plant, disinfect the containers by dipping or scrubbing them with water and bleach, 10 parts water:1 part bleach, and fill them with fresh soil.
  • If you grow tomatoes in the ground, move the planting bed each year to a new growing area.  This is called crop rotation.  Wait at least three years before planting in the same spot.
  • Destroy, do not compost, any infected fruit or plants.  Most home compost does not get hot enough to kill overwintering insects or pathogens. 
  • Turn your garden soil every fall after harvest.  This destroys any insect larvae that might overwinter. 

 


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