Tomatoes don’t often give one any trouble, but when they do, it can be terribly discouraging. Just picture my dismay when my summer crop of Roma tomatoes, which usually gives me enough tomatoes for sauces, cooking, salads, and a healthy store of frozen relish for the winter, failed spectacularly last year.
Of course, I’m not alone in this, and plenty of readers have been getting in touch to find out how Australian veggie gardening enthusiasts can steer clear of trouble with this veggie staple. As always, help is at hand. In this post, we’ll jog through the most likely tomato troubles, how to avoid them, and what you can do if they start rearing their ugly heads.
1. Blossom End Rot
Your tomatoes develop, but the bottoms of each fruit seem to rot away. Is it some dreaded disease? In truth, it’s a problem with how you’re growing your tomatoes (sorry guys). In essence, it’s caused by calcium deficiency, and the causes of that range from insufficient water to too much water, low calcium in the soil or sufficient calcium and an incorrect soil pH to make it absorbable. “Omgeeeee!” You exclaim. “What now?”
First up, think watering. Did you let the soil dry out? Did you water like crazy so that your soil was constantly soggy? If the answers to both these questions is a “probably not,” then we need to dig deeper.
Were you inclined to dig around your tomatoes a lot? Oops! You may have damaged the roots, and that would also interfere with water uptake. If you think they just got too dry, remember the benefits of mulch. Still not convinced you’ve targeted the problem?
You may need to have your soil tested to check its pH, or you can try one of the home soil test kits you can get at garden shops. They’re not as precise, but you can get a broad idea of your soil pH from them. Tomatoes absorb Calcium at a pH of 6.5 to 7.5. If your soil is acid, a little lime could be the thing you need.
Need a broader guideline? Inland soils in Australia tend to lean towards acidity, while coastal soils tend to be more alkaline. Whether you’re going to be more scientific or are going to take a guess, the good news is that the 0.5 around neutral pH range suits most plants well, and could prove to be a good general guideline for most of your plants
2. Fruit Cracks
Do your tomatoes seem to burst open at the stem end? Here’s why it happens. If water-stressed tomatoes suddenly get a heavy watering or rain, they drink the water up like crazy, and the fruits literally pop. Try to keep the soil evenly moist through the growing season so that your tomatoes don’t reach this state of thirstiness. A well-watered tomato plant won’t go into water-glutton mode even if there is good rainfall.
Too easy? Let’s try another.
3. Sun Scald
Everything’s looking good until yellow patches appear on the sides of tomatoes exposed to the sun. In general, this occurs when the top of the plant and it’s leaves aren’t providing sufficient shade for the developing fruits. Don’t over-prune your tomatoes, and keep them staked so that they don’t flop over and expose the fruit to the sun’s harshest rays.
OK, so that’s still an easy one. What else should we consider?
4. Low Fruit Set
Your tomatoes grew like crazy, flowered well, but didn’t produce many fruits. What could be the problem? Too much nitrogen in the soil could be the issue. If your plants tended to be softish with dark green leaves, you could be overfeeding.
Growing tomatoes too close together can also be an issue. They’ll self-pollinate, but if the spacing is too small, the pollen doesn’t find its way to the target because there is insufficient air movement. If you’re growing undernet, the net could also be part of the problem. Allow the right spacing, and give your plants a little shake from time to time during flowering to get the pollen moving.
5. Leaf Roll
Here’s another tomato issue that looks like insect or disease damage, but can be prevented through good garden practices. Leaf roll begins with older leaves, which yellow and curl up, and it can spread to affect most of the plant.
Soil that’s too wet, over-zealous pruning and an extra whammy of high temperatures are often to blame. The good news is that your plants should still produce fruit, but next season, try adjusting your watering and pruning – it could just improve your harvest! If your soil drains poorly, build up your beds a little and add lots of compost.
6. Bacterial Canker
Now we’re getting into nasty territory. Yellow spots appear on the fruits, and each is surrounded by a darker halo. There’s nothing to do but remove all infected plants and avoid growing tomatoes in the same soil for three years. This starves out the spores, and you’re good to go again.
Sorry, there’s nothing else you can do about bacterial issues. Anything that kills bacteria also kills plants. Rotate your crops!
7. Early Blight
This nasty plant disease causes spotty leaves that are surrounded by concentric circles of infected tissue. The infection dries out from the central point where the infection began and ultimately, the entire leaf dries up and falls off.
You can treat this problem with a fungicide, but to prevent it, the best method is to avoid growing tomatoes, eggplants, and peppers in a particular bed during successive years. As with other fungal diseases, watering to wet the soil while keeping the leaves dry will also help with prevention.
8. Septoria Leaf Spots
Yep! It’s another fungal disease. Big yellow spots develop central black ones with a halo of dying tissue around them. It looks a lot like most other fungal diseases, but luckily, telling one from the other isn’t that important: prevention and cure are similar enough to make the question unimportant.
Correct plant spacing, and keeping the leaves dry, particularly if you water in the late afternoon or evening, will help to keep your plants from getting this disease. Crop rotation is another preventative method, and you can weigh up whether you’ll use a broad-spectrum plant fungicide to slow or stop the infection if it occurs.
9. Fusarium Wilt
Fungi don’t just attack the leaves of plants: Fusarium destroys the vascular system that transports water through the plant. One branch after another wilt and dies off. Crop rotation (as described above) is your best defense, along with a choice of wilt-resistant varieties like Cherokee Purple and my favourite Roma.
Another type of wilt, named verticillium wilt, occurs in some gardens and should be combated in the same way.
10. Viral Diseases
Plants can fall prey to a variety of viral diseases too. These usually stunt the plant rather than killing it, and you may see odd mottling or distortions on the leaves or fruits. Happy, healthy plants can often resist viral diseases, so limit stress caused by poor nutrition and watering practices.
I’ve already helped plants to overcome the effects of a virus simply by feeding well, but rest assured, the virus is still present and can still spread. It actually becomes part of the plant’s genes! If you suspect a virus on one plant in your patch, it’s probably best to remove the entire plant so that the virus doesn’t spread and come back to haunt you later.
Insects and Tomatoes
We haven’t really discussed insect problems here, but just to touch on them, they’re usually less common. The advantage is that tracing the source of your issue is usually fairly easy. A bite is a bite, and you can usually see that something has been munching away. Some insects scratch the leaves and fruits rather than biting, but close inspection will reveal the little monsters.
If you’re worried about insects, make tomato cages or cover them with net. It’s not guaranteed, but chances are, you’ll have fewer problems. Good cultural practices also play a role here. Healthy plants have their own ways of combating attacks from insects or diseases.
In a future post, we’ll take a look at common veggie garden pests and how to get rid of them or prevent them from paying you a visit.
By now, you may have noticed a common thread running through these tomato problems. Poor nutrition, poor watering, plants that don’t have enough space, and plants grown on the same soil for season after season, are all recipes for trouble.
You can also “love” your plants too much – giving them too much water and food increases your chances of picking up trouble as does overzealous pruning. It’s not that difficult to get the balance right, however.
So, what happened to my crop of Roma tomatoes last year? Well, it didn’t take too much thinking to work it out. To my shame, it was simply a matter of choosing the same spot for my plants for three years in a row. I got away with it the second time around, but not the third. For a supposedly experienced gardener, that’s a facepalm moment, and I have only myself to blame!