It is easy to see there is a problem with this tomato plant, but it may be difficult to know how to help it. This plant is lacking Nitrogen (N), Phosphorous (P) and Potassium (K). I would err on the side of caution and encourage the owner to treat it as though it has Tomato Mosaic Virus until the tomato plant looks healthy again.
Nitrogen Deficiency in Tomato Plant
We can see the nitrogen (N) deficiency in the very yellow older leaves. As this deficiency continues the plant will become short, spindly and will wilt under mild water stress. Luckily, this deficiency can be remedied within days of applying nitrogen.
Adding Nitrogen to Soil
There are many ways to add nitrogen back to your soil and prevent it from happening in future crops. Nitrogen is a common fertilizer that can be purchased. If you prefer to naturally add nitrogen to your soil simply add composted manure or coffee grounds to your garden. You can also add nitrogen to the soil via companion planting or cover crops. Green manure crops (like Borage) or nitrogen fixing plants (such as peas or beans) work great for this.
Signs of Phosphorous Deficiency in Tomato Plants
We can see the Phosphorous (P) deficiency in the purplish undersides of the leaves. If this plant does not receive Phosphorous, the older leaves will develop a brown netted veining. Plants with a Phosphorous deficiency tend to look like young unstressed plants because their growth is stunted.
Adding Phosphorus to Soil
Adding phosphorus to your soil will improve the quality of your crops, root growth, stalk strength, and will allow your crops to mature earlier. Ground bone has been added to soil to replace Phosphorus for hundreds of years. Today it is common to add phosphorus to your soil by applying bone meal or rock phosphate.
Signs of Potassium Deficiency in Tomato Plants
The Potassium (K) deficiency is a little more difficult to spot because it can easily be confused for tomato mosaic virus. We can tell that this plant has a Potassium deficiency because of the tip burn on the leaves, dry tan scorch on the matured leaves, curling or the green leaves and the blotchy fruit.
Adding Potassium to your soil
Potassium helps plant fight diseases, grow faster, use water better, and take in other nutrients. There are many ways to naturally add Potassium to your soil. Simply add:
- Composted fruit and vegetable waste
- Ground up citrus rinds
- Banana peals
- Kelp meal or seaweed
- Wood ash
- Granite Meal
Signs of Tomato Mosaic Virus in Tomato Plants
This plant could possibly have Tomato Mosaic Virus, and I would treat it as though it does until the plant looks healthy. My primary reason for suspecting TMV is the necrotic spots in the fruit of the tomato. I would take precautions because TMV is highly contagious, has no cure, stays in the soil for up to 50 years, and can infect tomatoes, tobacco, beans, cucumbers, squash, roses, potatoes and peppers. You can control the possible spread of this disease by:
- Not smoking when transplanting
- Changing into clean gloves after you’ve had contact with the plant
- Boiling any tools that have come into contact with the plant for 5 minutes then washing with detergent
- Swiping your tools with bleach is NOT enough to kill this virus
- Make sure your other plants are healthy and free of nutrient deficiencies
If the tomatoes on this plant continue to exhibit blotchy fruit with necrotic spots after being treated with nutrients, I would assume it has contracted Tomato Mosaic Virus and take the following precautions:
- Burn all parts of the plant
- Clean the entire area
- Do not plant any plants that are susceptive to TMV in the area
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