Physiological Disorders

Blotchy Ripening

See Blotchy Ripening section of Tomato (Outdoor).

Blossom End Rot

See Blossom End Rot section of Tomato (Outdoor).

Fruit Cracking

Fruit cracking in tomatoes can be a serious market problem, reducing profits. The causes of fruit cracking are varied and are subject to debate by researchers. Several factors have an effect on fruit cracking. This can range from splitting to skin russeting.

Water uptake, humidity, temperature and soluble solids (sugars) as well as calcium nutrition and standing water on the fruit are thought to have roles in fruit cracking, along with genetics. Cultural practices can have an effect on fruit cracking. Water management, light levels and rate of fruit development can be affected by management practices.

Greenhouse growers should be aware of potential problems with increased fruit cracking in tomatoes with some cultural practices. Increased light and fruit growth can occur when new plastic is put on or with topping to increase fruit size. Watering schedules may need to be modified to reduce cracking under those conditions.

Irregular water uptake going from very dry to very wet plays a major role in fruit cracking. High temperatures also play a role. Irrigation can be used to modify both. Growers can increase the frequency of irrigation to prevent moisture extremes from developing under both field and greenhouse conditions. Overhead irrigation can also be timed to cool the crop in extreme conditions. High humidity and calcium nutrition are also associated with fruit cracking. Management practices must allow good transpiration rates as well as adequate calcium levels in the soil or fertilizer solution. Likelihood of cracking increases if tomatoes are allowed to ripen on the plant.

Soil-borne Diseases

The fungi Rhizoctonia, Pythium, Phytophthora, Colletotrichmum, Verticillium, Sclerotinia and Fusarium, the bacterium that causes tomato canker, and root knot nematodes may become established in greenhouse soils or survive in tomato roots left from a previous crop. Depending on which pathogen is present, rotation or the use of resistant varieties may be viable alternatives. Otherwise, steam or chemical treatment of the soil is necessary. It should be considered, however, that treatment of soil may not entirely eliminate the pathogen and, in the case of Pythium, Rhizoctonia and Fusarium, the pathogens may rapidly recolonize the soil.There is no effective chemical treatment for the wilt and decline diseases caused by Verticillium and Fusarium. The most effective management techniques are resistant cultivars and sanitation, including soil pasteurization.

pentachlornitrobenzene (Terrachlor 75 WP):  Rhizoctonia root and stem rot, damping-off ONLY. 4.0-8.0 oz/100 gal water. Soil drench application to seedlings. (REI 12h, Group 14).

propamocarb HCl (Previcur Flex): Pythium and Phytophthora species ONLY. 12.8 fl oz/100 gal water.    (REI 12h, Group 28).Prevent intense sunlight after application by applying Previcur Flex in the evening. Do not apply to dry rockwool or other dry growing media without first pre-wetting with water.

Streptomyces griseoviridis (MycoStop): 0.08 oz/lb seed Seed Treatment. 1.0-2.0 g/ cubic yd Soil incorporation. 1.0-2.0 g/100 ft Soil Drench. (REI 4h,Group N/A). Biological control.

Trichoderma species ( RootShield, Plant Shield, SoilGard): See labels for specific instructions. (REI 0h, Group N/A). Biological control.

Viruses

Refer Tomato (Outdoor) for a discussion on viruses.