Taking Care of Your Tomatoes
Tomato plants are susceptible to many seasonal diseases and conditions that impact plant health and reduce yields. Although many challenges exist from plant diseases to soil born pathogens, there are some strategies you can take to lessen risk and improve yield. Strategies include both pre-plant and post-plant steps, so if you already have plants in the ground, consider employing post-plant strategies this year and plan to include pre-plant strategies in the next growing season. Soil borne diseases have different impacts and the control methods are different.
Variety selection is the key to reducing disease risk. If a large harvest is your goal, choose disease resistant and early producing varieties. Some great choices that will work well across our area are: Big Beef, Celebrity, and Early Girl. Many Roma and cherry tomatoes perform well throughout the growing season too. Along with variety selection, grafted plants are also an option to help prevent disease. You can expect to pay a little more for the security of disease resistant rootstock grafted onto the heirloom scion (fruit producing top) that produces the traditional tomato that your taste buds crave.
Spacing and trellising limits the spread of disease by increasing the ventilation around plants. Choosing to plant one row of tomatoes per bed, at 18”-24” in-row spacing allows for good ventilation on a variety of trellising structures. Growing Big Beef tomatoes on a line trellising system similar to what you would use for pole beans can lengthen the production season and the plants adapt well to single leader (trunk) pruning. In contrast, using cages with large hand-space openings with a determinate type tomato, like Celebrity, works very well to hold in more side growth typical of the variety.
Regardless of your pre-plant decisions, there are some post-plant strategies that can decrease disease risk too. Pruning plants and cultural control methods such as good sanitation and debris removal provide lots of benefits, many impacting disease control. Starting at the bottom of the plant, prune off the lower leaves that come in contact with the ground or mulch. As the plant grows and builds more upper foliage, prune lower leaves up to the first flower cluster. This removes lower leaves that may be loosing the power of cell division and growth due to plant age, reduces plant contact with the soil surface and limits potential entry points for disease to enter the plant. Prune as close to the plant stem as possible to reduce entry points for disease. Remember to REMOVE infected plants as soon as you find them. Removal of diseased plants is the most important step in reducing disease spread. Be sure to properly clean and disinfect the cutting tools after you work on a plant.
Scout for insects frequently. Insects not only cause chewing damage to plants and fruit but can also spread disease. Noting insects and keeping populations under control can reduce disease risk. A few insects to look out for are: leaf hoppers, white flies and thrips. Check leaf surfaces, underneath foliage and in the flowers. Observe insect populations and take cultural and/or biological control measures when needed. Cleaning up the area, removing dying leaves and making sure you have good air flow through the plant is the first line of defense. Know your good bugs from the bad. Remember lady bugs are your friends. They’re there to dine on the bad actors like aphids.
Irrigation can influence disease as well. Apply water in the morning to limit the length of time the plant foliage is wet. By watering in the morning, all moisture on the foliage will evaporate leaving the plants dry for the rest of the day and into the night. If using drip irrigation, the problems that come from leaf wetness are reduced, although AM and early PM watering is still recommended for efficient water use by the plants.
Many tomato diseases are either bacterial or fungal and can be treated with a broad spectrum application of appropriate products, if needed. For instance, early and late blight, both very common issues, can be prevented/treated with a copper fungicide.
Tomatoes ripen from the inside out, so full color on the outside means the fruit is ripe all the way through and susceptible to bruising and damage. Fortunately, tomatoes ripen off the vine. Picking the fruit at an early to mid-breaker stage can give you a bit more flexibility in handling and damage control. If they are showing a bit of color at the “shoulder”, you can pick them and let them ripen inside. Keeps the pests off them as well.
For a more information on growing tomatoes as well as tomato problems and diseases take a look at https://content.ces.ncsu.edu/growing-tomatoes-in-the-home-garden
Minda Daughtry is Horticulture Agent for North Carolina Cooperative Extension in Lee County.