Grey Leaf Spot Disease in Tomato Plants

So you're got what you think is a flourishing garden, your tomato plants look beautiful until one day you go out and notice that something is wrong with the leaves on your plants. If the leaves have small dark spots that grow bigger and darker each day until the spots are grey, then you've got the dreaded Grey Leaf Spot disease.

While it is alarming, there are steps that you can take to rid your plants of the disease. This article will give you information on what Grey Leaf Spot is, what causes it and how to get rid of it.

What Grey Leaf Spot is:

Grey Leaf Spot is a fungal disease that causes lesions on the generally older leaves on tomato plants in form of brown or black specks. The specks change color over time and grow larger (1-2 mm). They can stay brown or turn into spots that have a grey center with surrounded by yellow. Holes (shot holes) can go all the way through on the leaves. There can be several spots on a leaf but they don't generally fuse together and remain separate on the leaf that they are on. The spots on a leaf may make the leaf itself change to yellow, then brown and fall off the plant.

AVRDC.com states that "defoliation can be severe, leading to sunburn damage of the fruit." Younger steams may occasionally get lesions but it's not as typical as on older leaves. Bad infections WILL cause tomato production to slow or stop.

Causes of Grey Leaf Spot:

The disease is usually found in areas that have warmer climates where fungal spores thrive. It is caused by fungi titled Stephylium solani. The spores are spread by floating through the wind and landing on the plants. In humid areas it spreads even more quickly. It can also spread if you use an overhead sprinkler.

Treatment for Grey Leaf Spot:

Check out your tomato plant thoroughly. If the entire plant is infected, unfortunately you have to chuck it so it won't spread to your other tomato plants. If it is salvageable, you'll want to remove the affected leaves and the leaves that have fallen on the ground. If the tomato plant in question still has Grey Leaf Spot after you've tried to save it, you'll need to remove the plant entirely.

Kay Klier has a tomato FAQ and says that a Bordeaux mixture will help with Grey Leaf Spot. The mixture is made out of copper sulphate and hydrated lime. You can find out how to make it here.

If you'd rather use a spray that comes in a bottle, there is a brand called Garden Fungicide that helps with disease control. It is available through EcoSmart.com and you can search for a retailer near you by clicking this link.

Sources:

http://www.avrdc.org/pdf/tomato/gray_leaf_spot.pdf

http://home.earthlink.net/~shelly.johnson/tomato.html

http://en.wikipedia.org/wiki/Bordeaux_mixture

http://www.greenfingers.com.au/services/digging_deeper/tomatoes_want_to_grow/5.htm