Tomato Care & Repair

Most tomato plants are like demanding prima donnas. Everything needs to perfect all the time, otherwise they will play up. Add to that Tasmania’s fickle climate and you find that even the most experienced food gardener struggles at times. This blog post might help you make things ‘just right’ for your tomato plants or improve things if they tell you that they are not happy.

How to make the most out of your tomato plants

Resistant tomato varieties - Most of us choose tomato varieties focusing on the fruit they will produce, but your task of taking care of the wellbeing of your tomato bushes will be a lot easier if you choose varieties that have a natural resistance against diseases. Sweet Bite tomatoes, for instance, are widely described as ‘disease resistant’. There are also hybrid tomato varieties that were bred specifically to resist certain diseases. See seed packets for details. Disadvantage of using hybrid tomatoes is of course that you can’t save their seed (see blog post Heirlooms and Hybrids on this blog). Most heirloom varieties are vine (indeterminate) tomatoes. Some of the suggestions mentioned below are much harder to use on bush tomato varieties (determinate). 

Rotate your crops – please don’t plant your tomatoes where last season you grew potatoes or tomatoes or other members of the Solanum family because pests overwinter in soil. Some will gladly visit potatoes one season and tomatoes the next. Crop rotation is a great way to avoid pests. Crop rotation is covered on this blog in The importance of rotating crops on this FGG blog.

Don’t plant too early - exposure to cold and/or wet conditions can create the perfect conditions for fungi and viruses. Root systems can’t develop well when it is too cold. In Tasmania, if Spring is not too cold, the start of November is a good time to plant tomatoes in the garden. However, there have been La Nina Springs where 1 December was a better time.

Prepare your soil - plant tomatoes in soil that contains plenty of compost, but make sure it does not contain too much nitrogen because that would result in large tomato bushes with lots of leaves and not a lot of fruit. Too much nitrogen can also contribute to Blossom End Rot (see below).

Give them some space - Ideally you plant tomato seedlings far enough apart so when plants reach their full size they still don’t touch each other. Easier said than done in a small garden, I know, but it is totally preferable because this lowers transmission of diseases between plants and gives better ventilation. At least 60 centimetres between plants will make a big difference.

Attract beneficial insects – plant small flowering plants between your tomato plants so beneficial insects that love the flowers will also feast on the non-beneficial insects in your tomatoes.

Mulch - Mulch will make it far less likely that fungus spores will splash up onto leaves from the soil. Mulch will also of course diminish evaporation, so there is less chance that your soil will go moist, dry, moist, dry.

Water from below - Regular irrigation from above means that tomato leaves are wet regularly. Wet leaves are loved by fungi and viruses. If you irrigate from above, please do this in the morning, so water evaporates when the temperature goes up.

Prune regularly - Remove leaves that touch the soil and that touch other tomato plants, so easy pathways for fungi and viruses from one plant to another are cut off. This is much harder to achieve for bush tomatoes that are naturally wider.

Prune vine tomatoes - Prune vine tomatoes to just two or even one main stem to create good ventilation and to get larger tomatoes. Stake or trellis vine tomatoes, so they never rest on the ground.

Ventilate – In hothouses have windows and door open or have fans so there is ample ventilation to keep temperature and humidity down.

Shake to pollinate - Tomatoes mostly pollinate themselves, either by using pollen from the same flower or pollen from another flower on the same plant. Out in the garden self-pollination is often achieved by wind or vibrations that insects create. In a hothouse you may want to give plants a quick shake every few days to improve pollination.

Avoiding diseases or slowing them down

Prune away affected leaves - Remove leaves as soon as they don’t look healthy, to give the plant more time to ripen its tomatoes before it is affected too much. Feeding an affected plant may give it what it needs to form new unaffected leaves. Result may be that the plant recovers and gets rid of the disease that was attacking it.

Clean your secateurs - when you move from one tomato plant to another clean your tools with methylated spirits or some other chemical to avoid transfering pests and diseases. One food garden group member suggested you have two pairs of secateurs, so the one you just cleaned has time to dry before you use it again.

Exclusion – damage caused by insects or rodents can be avoided by netting your tomato patch or bagging individual tomatoes into small nets.

Prevent or remove Mildew – Mildew is a whitish fungus that settles on tomato leaves and weakens them. Milk has an antiseptic effect on mildew (only on mildew), so it can be used to prevent it or get rid of it. You can make the spray yourself. The recipe can be found here.

Prevent or remove fungi – Fungi can be discouraged from taking hold by lowering the pH on tomato leaves and stems with baking soda. Spray once a fortnight. You can make the spray yourself. The recipe can be found here.

Remove non-beneficial insects – sap sucking insects that fly from plant to plant can be the major reason that fungi spores and viruses gradually spread from plant to plant. A good example is whiteflies that are often found in hothouses or other warm not-well-ventilated environments. Non-sap-sucking insects, however, are good to have around tomato plants, so be careful not to eradicate both beneficial and non-beneficial ones by spraying broad-spectrum pesticides, if this is not needed. You can find info about eradicating whiteflies in Pest-Control Quick Guide on this blog and under Neem Oil below.

Completely remove a plant - rapid deterioration of a tomato plant may tell you that the best response is to remove the whole plant carefully. The plant may be affected by a virus or bacteria. For many of them there is simply no cure. When you do this, make sure that the plant or you or your tools do not touch any other nearby tomato plants.

Do not compost - don't compost diseased tomato plant material, but remove it from your garden.

Do not save seeds from diseased plants - saving tomato seeds from heirloom varieties (see blog post Heirloom and Hybrids on this blog) is a great way to have your favourite varieties for many years without any expense, but never save seed from diseased or otherwise under-performing plants. Some tomato viruses are actually transferred to the next generation via seed!

Problems that are NOT caused by pests or diseases

Here are four problems with tomatoes that are in fact not caused by a pest or disease.

Cracked Skin - Tomatoes crack or split when rapid changes in water availability cause fruits to expand faster than their skins can stretch. Cherry tomato varieties with thin skins are much more susceptible to cracking than large varieties. It can be hard to avoid skin cracking in cherry tomatoes.

 

Curly Leaf – leaves have a healthy colour but are curling inwards and upwards. Thoroughly water the plant from below, then check early the next morning. If the leaves are no longer curled, the curling was the way in which the plant avoided evaporation through its leaves, because there was a lack of water.

Cat Face - This condition is caused by unfavourable growing conditions, for instance low temperatures during flowering, or poor soil. It is easily recognisable because of the brown scar tissue (see photo below). Occurs most often on the first-formed fruits because temperatures at the start of the season are too low. Large tomato varieties are much more susceptible to Cat Face than small cherry varieties, so you may be able to avoid it by starting the season with cherry tomatoes and sowing and planting large tomato varieties later.

Affected tomatoes can be eaten. If conditions improve, new tomatoes on the plant won’t have the problem.

Blossom End Rot is the name for rotting at the bottom end (the blossom end) of the fruit. It is caused by a lack of calcium. Tomato plants get their calcium in the water that they take from the soil. Most soils contain plenty of calcium, but if the soil is sometimes too dry, the plant can’t take up the calcium it needs. Regular sufficient watering is the answer.

Things get worse if temperatures are high or if there is a lot of wind. Large tomato varieties are much more susceptible to Blossom End Rot than small cherry varieties. This is not a disease and it won’t spread if you improve your watering. Roma-type tomatoes are particularly susceptible apparently.

Sunburn - Tomatoes can get burned by the sun if there is prolonged extreme heat and direct intense sunlight. In Tasmania it is rare to have sunburnt tomatoes, even after a few days of higher-than-normal temperatures. However, if a tomato plant is in a very sunny, very sheltered spot, if the un-mulched soil around it is hot, and the plant lacks water to cool it down, it can happen, as the photo below (thank you Troy!) proves. The photo was taken after warm weather in January in a sheltered garden at Old Beach.

If sunburn is a problem in your garden, cover plants with 50% green or black shade cloth on hot days. Mulching their soil will keep moisture in and temperatures down. Adequate water at all times will also help.

Tomato plants in hothouses might have the same problem if exposed to long periods of intense sunlight and heat, but once again, this is rare in Tasmania. In hothouses, improving ventilation is the first step to this not happening again.

A sunburnt tomato will be affected by mould if left on the plant, but if you remove it soon after the sunburn occurs, the unaffected part of it can be eaten without any problems.

If you have had sunburnt tomatoes in your garden your plants may benefit from less pruning than you normally would, so tomatoes are shielded from the sun by leaves.

Problems that ARE caused by pests and diseases

Tomato pests and diseases are caused by insects, fungi, viruses or bacteria.

You would hope that the diseases are easily identified by examining the leaves of a plant. The reality is that the damage to tomato leaves and fruit by a variety of fungi, viruses or bacteria can look quite similar unless observed through a microscope, so often it is not completely obvious what disease has caused the damage.

 

That is no big deal because in most cases it is not crucial to know the exact name of the disease. The way of dealing with the problem for those who want to grow food organically is nearly always the suggestions above.

Copper fungicides used in winter to protect stone-fruit trees against Curly Leaf is often mentioned as a way of killing tomato fungi and even viruses. However, spraying these chemical substances on tomato bushes that have fruit on them is much more concerning than spraying it on bare trees in the middle of winter. Thoroughly wash tomatoes before eating if you choose to use this pesticide.

Neem Oil is a pesticide for getting rid of sap-sucking insects that affect tomatoes, especially whiteflies. Neem oil is approved under many organic certification schemes. There are products that claim to be Neem oil in which Neem oil is only a minor component. Neem is broad-spectrum, so it kills all chewing and sucking insects. Opinions are divided regarding toxicity of Neem oil to humans. Have a look at Neem Oil Fact Sheet for more info.

For those who want to know a bit more ….

Fungi arrive as spores on the wind and visiting insects such as whitefly, are easily spread via tools, splashing water, moist leaves and in humid conditions. Copper fungicides can help. Fertilisation of plants so they grow more leaves after you remove affected ones is also a good thing. Some tomato fungi also affect potatoes. Examples of fungi are: Powdery Mildew, Black Spot, Early Blight, Late Blight, Verticillium Wilt, Septoria Leaf Spot, Tomato Leaf Mould, Fusarium Wilt.

 

The spots on these leaves point to Early Blight

Fusarium Wilt causes root and stem rot

Viruses are very small and not visible to the naked eye. Most viruses are spread by insects, in particular aphids, but some are spread through tools that were used on infected plants. Virus infection causes a wide range of symptoms including unusual colour patterns in leaves and fruit, distorted growth, plant stunting, reduced yield and plant death. Insecticides are often not effective because plants become infected before the insects succumb to the insecticide. Examples are Mosaic and Tomato Leaf Curl.

Bacteria are microscopic single-celled organisms. Bacteria multiply rapidly by simple cell division. Bacterial pathogens are introduced to new sites on contaminated seed or transplanted plant material. With most bacterial diseases there simply is no effective pesticide. Examples of bacterial tomato diseases are Bacterial Spot, Bacterial Speck, Bacterial Canker and Bacterial Wilt.

Please email me your feedback

Please contact me on foodgardengroup@gmail.com if you have other tomato management methods that work for you or additional comments or if you feel that some of the info provided here is not accurate. I am keen to learn from you!

For more information on this subject I recommend

• Oklahoma College of Agriculture: Common Diseases of Tomatoes Part 1, 2 and 3
• Youtube Stop worrying about tomato diseases
• DeBacco University: Top 10 Plant Problems 2019

I hope you will have a bountiful crop!

Max Bee