Posts Tagged ‘Early blight’

Tomato problems are popping up all over the place, with plants suffering everything from early blight to bacterial speck.  If your tomato’s looking peaked, check out the symptoms against this list of possible culprits.  For more extensive information, click here for the CSU Extension fact sheet on recognizing tomato problems.

 Symptom: Leaves chewed to a nub, large pellets littering the area below the plant.   hornworm

Culprit:  Tomato and tobacco hornworms are large green caterpillars with white stripes and a soft, flexible horn on the hind end.  Like hungry teenagers, they quickly strip plants of leaves and damage fruit.

Cure:  Hornworms are easy to control.  Courageous gardeners pick them off by hand or you can apply Bacillus thuringiensis(Bt), an organic product that gives hornworms a deadly bellyache.

 Symptom: Leaves turning yellow with purple veins.  Fruit is small and tasteless, and the plant looks as if sugar were spilled on it.

Culprit:  Psyllids, small sap feeding insects whose saliva causes the plant to grow oddly.  Look under leaves for the scale-like nymphs.  Their waste, called lerps, looks like sugar.

Cure:  Tiny Psyllids can mean big problems for tomatoes, severely stunting fruit, so at the first sign of these bad bugs, spray with insecticidal soap.  This is limited help, though, and you may need something stronger. 

Symptom:   Green plants turning blond, yellowing from the bottom up.  Older leaves have brown spots with concentric rings, and sometimes stems or fruit is blemished.     early blight

Culprit:  Early blight is a fungus spread by water, insects, and gardeners.

Cure:  Pick off diseased leaves, and keep the ground free of debris. Dust healthy leaves with sulfur to shield them from infection.  Or you can try potassium bicarbonate, talked about in a previous post.  Give plants room to grow without crowding them, and use drip irrigation to prevent splashing water.  

Symptom:  Black, sunken, rotten spots on the bottom of fruit.

Culprit:  Blossom end rot, caused by poor uptake of calcium.  Though calcium is plentiful in our soil, irregular watering and excessive heat prevent the plant from using it. 

Cure:  Use a timer to automatically turn on and off the irrigation, and mulch plants to keep the soil from drying out too rapidly. 

 Symptom:  Fruit with bleached-out soft spots or unripe, green shoulders.

Culprit:  Intense sun and high heat are too much of a good thing for tomatoes, causing sun scald, poor fruit set and unripe spots.  green shoulders

Cure:  Canopy the plant with shade barrier cloth draped on support poles above the plant. 

 Symptom:  Limp, wilting leaves that don’t perk up in the evening or after watering.  Older leaves yellow and die, often affects just one side of plant .  Plant may be stunted with few tomatoes.

Culprit:  Fusarium Wilt, which blocks the water transport system of the plant.  Tomatoes that are labelled VFN are resistant to this disease, but heirloom varieties may suffer.

Cure:  Pull and destroy the plant. The problem remains in the area for several years, so plant your tomatoes, eggplant, potatoes and peppers in another spot for the next three seasons.

 Symptom:  Mottled yellow and green leaves, or leaves with purple spots.  Plants are small, yellow and bushy.  Leaves are misshapen and look stretched out like taffy.   virusFruit has yellow rings and spots.

Culprit:  Cucumber mosaic virus or tomato spotted wilt virus.  Viruses can cause odd-looking problems.  If you notice your plant suddenly looking like it’s from outer space, with leaves elongating like a shoestring, becoming curled or cupped, it may be a virus. 

Cure:  Viruses can’t be cured, so pull and destroy the plants.

 Symptom:  Leaf spirals, cupping or distortion.

Culprit:  Tomatoes are sensitive to herbicides. Many gardeners don’t spray their food plants; instead, the damage is from drift.  Drift can occur from applying weed killer on windy days. 

Cure:  Limit applications of weed killer to cool times of the day when wind is calm.  herbicide

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It seems like the problems are coming fast out in the vegetable patch.  One that I’ve battled every year has reared its ugly head:  early blight on the tomatoes.  This fungus gets its jollies by attacking plants as the temperatures soar, and now that we’ve gotten toasty warm outside my plants are showing their first signs of disease.

Early Blight is the common name of the fungus Alternaria solani.  It overwinters on leaves or other plant parts left in the garden, then colonizes the plant by spores splashing up during irrigation or driving rain – something we’ve had a lot of this season.   early blight

 Once symptoms show they appear as brown to black, target-like spots on older leaves lower on the plant.  Effected leaves turn yellow, then drop from the plant.  Once this begins it seems that the rest of the summer is a race against the disease.  Fruit may or may not be effected, and you can still get plenty of love apples from the vine.  But in severe outbreaks the fruit is ruined. 

In the long term, good sanitation in the garden is the way to keep the disease pressure low:  cleaning up all fallen leaves every fall and destroying them.  Experts recommend rotating tomato plants out of the area for a couple of seasons, but in a backyard this isn’t exactly do-able.  I have one vegetable garden and the plants will have to get tough or suffer.  earlyblight3

Spacing plants far apart to get good air circulation is another way to keep disease low.  I’m a big proponent of this and try to give my plants plenty of room when I pop them in the ground.  But they have a nasty habit of growing, filling out and touching one another, then all hope for order in the garden is lost to chaos.   Vines ramble where they want, grapes reach out to throttle their neighbors, the tomatoes stick shoots out at odd angles and the pumpkins produce leaves big enough to diaper a baby – there’s no such thing as good air space when August rolls around.

Fortunately this season I have a new weapon to try in the battle for tomato dominance:  Potassium Bicarbonate, a.k.a. Green Cure.  This organic fungicide was developed by Dr. Ken Horst of Cornell University to combat many fungal problems on roses, but it is also labelled for use on tomatoes and other crops.  Green Cure

Dr. Horst found that potassium bicarbonate keeps fungus at bay, although it doesn’t completely eliminate it.  It’s useful on early blight, powdery mildew (I’m keeping an eye on my squash for that) and other common leaf problems.

 Green Cure is a wettable powder – you mix a couple of tablespoons in a gallon of water and spray it on the plant.  As with ALL pesticides, organic or not, read and follow the lable.  I like to spray early in the morning, before breezes kick up and the sun becomes intense on the leaves.  With this product, coverage of upper and lowersides of leaves is important, and will have to be reapplied every two weeks until I decide I’ve had enough tomatoes.

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