Home Garden Resource 

Volume 12 2006

 Ask The Expert 

Q: Hi I wanted to know what is it when your leaves on your tomato plant turns yellow ? Am I watering to much? thanks for your help, 

Cindy Boyer

Hi Cindy
There could be several cause for your leaves turning yellow and yes over watering is one of them however here are some other things that could be causing yellow leaves on tomato plants and their solution:

Whiteflies and aphids: These can both cause leaf yellowing and leave a characteristic sticky excrement called honeydew. Leaves appear shiny and are somewhat sticky when honeydew is present. Damage usually is minimal on tomatoes and often can be ignored. If aphids become a problem, some applications of
insecticide soap are effective.

Early Blight: This is the result of a fungus infecting the foliage causing a disease known as early blight. Early blight is an annual problem for most gardeners. It normally develops into a problem when plants have a heavy fruit set and the area has received rainfall. Spores from the fungus are spread to the lower foliage by wind and splashing rain. Leaves must be wet for infection
to occur. At 50 degrees F. the leaves must be wet for 12 hours for infection, but at temperatures above 59 degrees F., the length of time for infection is only 3 hours. Leaf spot development is most severe during periods of cloudy days and high humidity. To control the fungus, foliage applications of a fungicide must be made every 7 days until moist conditions (dew included) no longer exist. Applications should begin when the first fruit is slightly larger
than a quarter.

I hope this helps

Tomato growing guide

 

Sign up for our free newsletter and never miss a new article

 

Quick tips for a healthier lawn.

Mow high. The shorter you mow your lawn, the more work you will need to do to keep it looking good. Never cut more than a third of the plant when you mow. If you want to keep your lawn mowed to just 1 inch, that means mowing when it reaches 1.5 inches, or every 2 to 5 days. That's a lot of work. Mowing that close can weaken root systems (making the grass more prone to drought), and makes it easier for weeds to out compete grass. Mowing your lawn to a 3-inch height helps grass compete with weeds. It means mowing when the grass reaches 4.5 inches, or every 5 to 15 days, depending on growth rates.

Keep your mower sharp. Dull blades tear grass instead of cutting it. Lawns mowed with dull blades use 30 percent more water. Plus the wounds created by dull blades allow disease pathogens to enter grass plants. File your blade regularly, and replace damaged blades.

Leave the clippings. Clippings do not create thatch, contrary to popular belief. If you cut only a third of the plant at each mowing, the clippings won't smother the grass either. Mulching mowers work best to chop up clippings so they can settle down through the grass and onto the soil surface. There, earthworms incorporate clippings into the soil, improving both its drainage after storms and ability to hold water during drought. Do not disperse clippings onto pavement or into gutters. They are high in phosphorus and can cause pollution when washed into storm sewers and reach streams and lakes.

Don't fertilize early. Fertilizing in early spring only stresses grass plants over the long term by encouraging excessive top growth at the expense of roots. (Do not apply fertilizer to frozen or saturated soil, or on top of snow. It's a waste of fertilizer and sure way to have it wash into streams and lakes.) A better strategy is to fertilize in fall, from about August 15 until about 2 weeks after last mowing. Plants will use this fertilizer to develop root reserves to help them survive through winter and get off to a healthy start next spring. 

Watch your water. It's easy to do more harm than good. Never water at night. Wet grass invites diseases. Water between 4 a.m. and 8 a.m. when the leaves will dry quickly in the morning sun. During extended drought, stop watering and allow grass to go dormant. More on watering.

Special care in shade. Grass needs a minimum of 4 hours of direct sun -- 6 hours if it gets much foot traffic. Anything less than this, you should consider other ground covers. In shady spots, plant fine fescues that are adapted to lower light, mow high and reduce fertilizer. 

Spray sparingly. Never use lawn insecticides without scouting to see if the problem justifies treatment. 75 percent of lawn insecticide applications in New York are unnecessary or ineffective. Manage grass for healthy root systems, which can tolerate some insect damage and remain aesthetically pleasing. 

Fill in weak spots. Use a rake to work up and improve the soil where weeds flourish or the ground is bare. Then reseed with grass varieties best-suited to the site. If, after a season of mowing high and leaving the clippings (taller grass will help shade out weeds), your lawn is still more than half perennial weeds and bare spots, consider a complete.

You don't have to become a lawn expert to have a healthy lawn. Just follow these simple tips and you'll be well on your way. For more details, follow the links from each tip, and explore our Lawn care menu.

Information provided by:
Department of Horticulture, Cornell University