Tomatoes face their fair share of pests and diseases and this can seriously affect the amount of fruit they produce. Weather conditions play a role in whether the pest or disease will become a problem. The best way to manage the accumulation of pests and diseases is to practice Integrated Pest Management (IPM) and crop rotation. By using these two methods, you do not need to rely on heavy chemicals. IPM is using physical/mechanical, biological, and chemical controls to manage pests and diseases. Crop rotation falls into the physical/mechanical group, as tomatoes are planted in a different bed each season.
Viruses, bacteria and fungal diseases can enter the plant through wounds such as broken stems or through the roots or be transferred by sap-sucking insects such as aphids, whiteflies, mites and mealybugs. Pathogens can also be spread by wind and water.
Tomatoes are a summer/warm weather crop and are susceptible to fungal diseases that require moist conditions to thrive. The main fungal diseases are wilt and mildew. These diseases multiply by spores. Ideal conditions are: warm temperatures, moist air, and a host plant such as a tomato. The spores can also survive in soil, dead plant material, and weeds growing nearby.
Signs of wilting are that the lower leaves turn brown and papery, look dry and droop, while the upper growth still looks healthy. The lower leaves seem to need water. But the disease interferes with the roots’ ability to absorb moisture. Watering actually makes the problem worse.
There are two types of mold: downy and powdery. Downy mildew is characterized by white spots or patches on the upper and lower parts of the leaf. Characteristics of powdery mildew are that the fungal spores start out as tiny white dots that gradually spread across the entire leaf. It also affects buds, stems and fruits.
Pest and disease control measures:
- Buy healthy seeds and seedlings
- Practice crop rotation
- Pick the leaves off the ground and destroy them, don’t compost them.
- In winter, sprinkle the soil with lime sulfur, which kills fungal spores.
- Do not water from above as this can spread fungal spores.
- ground level water
- Plant grafted tomatoes as they are more resistant to pests and diseases
- Make sure there is plenty of sunlight.
- Make sure air can circulate around the plants.
- Do not continue to feed the plants with nitrogen, as it creates soft, juicy leaf growth that is susceptible to attack.
- Make your own fungicide. See below for the recipe.
- Apply fungicides early in the morning.
Fungicide recipe:Mix one level teaspoon of baking soda in one liter of water. Add a quart of skim milk and a dash of Condy’s Crystals which you can get from a breeder (someone who supplies horse owners). Shake well and spray on leaves. It only lasts about 1-2 days in the bottle.
Blossom-End Rot is a physiological disease caused by too little calcium or too much nitrogen. As for calcium deficiency, it does not mean that the soil is lacking in calcium. There may be calcium in the soil, but the pH may be wrong, preventing the plant from accessing it. Tomatoes like soil with a pH between 5 and 7. If the pH of your soil is acidic and below 5, the plant may not be able to absorb calcium. To overcome this problem, an application of garden lime is recommended. This will raise the pH of the soil and allow the plant to access the calcium that is present in the soil. When you’re preparing the soil to plant your tomatoes, a good handful of lime per plant will help.
Tomatoes also attract their share of pests like whiteflies, aphids, mealybugs and spider mites. These are sap-sucking insects and some have the ability to multiply asexually. That means the female can produce many clones without the male. It is important to control these pests because they can transmit viruses and bacterial diseases.
I recommend that you use low toxicity sprays like Long Life Pyrethrin or a homemade chili or garlic spray. These types of sprinklers are called contact sprinklers and they wash out easily after rain or watering. They are not absorbed into the vascular system of plants like systemic aerosols such as Confidor. If you read my article Plant pests and diseases you will find recipes to make your own pesticides. One sign that your tomato is being attacked by sap-sucking insects is that the leaves are curling, bubbling, or turning silvery. When applying contact sprays, it’s important to spray it on the pests, so I suggest you look under the leaves because that’s where a lot of pests cohabit.
Some cultural tips for growing healthy tomatoes
- Put the plant in full sun.
- Check the pH of the soil and modify it accordingly if you need to.
- Don’t over-plant the garden bed.
- Prepare the soil properly before planting with compost, blood and bone, potash, and animal manure.
- Put down a shade cloth if the day is going to be extremely hot.
- water in the morning
The nice thing about growing your own tomatoes is that you control what pesticides you apply to them. If you decide to use heavy chemicals it is vital that you follow the withholding period instructions. The holding period is the number of days you must wait until you can harvest the product.
Growing your tomatoes is very rewarding, but you have to control pests and diseases, otherwise you will find that your efforts are being wasted. Observing and understanding what tomatoes require is the secret to growing healthy tomatoes. Integrated pest management and crop rotation are invaluable tools that, if you put them into practice, will reward you with delicious tomatoes without using heavy, nasty chemicals.