- Question : My tomato fruit develops a large black spot on the bottom of the fruit when it nears maturity. What causes this?
Answer : BLOSSOM END ROT OF TOMATOES, BLACKHEART OF CELERY. Blossom End Rot of tomatoes and peppers and Blackheart of celery are physiological disorders caused by a lack of calcium in the soil and /or and uneven moisture supply during the growing season. It is not caused by a disease organism.
Blossom end rot appears as a circular browning, black leathery area on the bottom of the blossom end of the fruit. Secondary disease organisms can enter through the damaged tissue and cause further breakdown of the fruit.
Blackheart of celery occurs in the youngest tissue of the celery plant (the heart). Affected tissue in the center of the heart dies and turns black while the outer, older tissue remains green. Secondary disease organisms can also cause further tissue breakdown.
Injury occurs gradually and is not usually visible until later in the season when the fruit is close to maturity. Tissue damage occurs when hot, dry periods alternate with periods of heavy moisture which results in an uneven or deficient supply of calcium to the developing plant or when calcium availability is affected be excessive use of fertilizer. Periods of rapid growth can also increase the potential for problem development. As calcium is required for fruit tissue and cell wall development, the deficient tissue does not develop properly.
To prevent the development of blossom end rot, ensure there is an adequate supply of calcium in the soil (through the application of lime), and provide a constant supply of moisture throughout the growing season. A rule of thumb is 2.5 cm of water per week for good growth. Mulching the soil will also help to maintain adequate moisture levels. Foliar applications of calcium nitrate or calcium chloride, made periodically throughout the season may be required to prevent the development of blackheart in celery.
- Question: My turnips and rutabagas have a woody texture inside the core and are often brown or hollow on the interior of the root. What causes this?
Answer: BORON DEFICIENCY. Boron, a micro-nutrient, is required by some vegetable crops for proper development and a deficiency can cause serious problems in crop development. The most common problems associated with boron deficiency are Brown Heart of turnips and rutabaga, hollow stem and stem discoloration in broccoli, browning of cauliflower curds, and Black Spot in beets. Of these crops, turnips, rutabagas and beets are the most severely affected by boron deficiency. Brown Heart can be found in turnip and rutabagas by splitting open a root where firm, water-soaked patches occur on the flesh. The tissue may eventually turn brownish and become pulpy and hollow. Affected roots will not store well. To prevent problems with boron deficiency, apply soluable boron (ie. Solubor, or Borax). Be careful during the application as many crops are sensitive to boron. Check for crop sensitivity and tolerence levels. Drift will cause leaves of sensitive crops to be burned and growth damaged. Residue in the soil can also cause problems the following year for sensitive crops. A general rate of Solubar (20% boron) would be 20 grams per 30 meters of row in approximately 10 liters of water (for crops with a high requirement for boron). Borax (10%) would have to be applied at twice this rate (40 grams per 30 meters of row). This application could be made to the row before planting or drenched on the row 5 weeks after planting. An alternative method of application would be to split the application - apply a drench 4 weeks and 6 weeks after planting. This will help to avoid toxicity problems.
- Question: My tomatoes and potatoes loose their leaves by mid summer, prior to that they have brown / black spots on the leaves. What causes this?
Answer: Early Blight is an annual problem of tomatoes and potatoes in the home gardens of Atlantic Canada. It is somewhat misnamed as it can appear in the garden at any time and is usually found around mid-August (especially as tops begin to mature). It is a foliar disease caused by the fungus Alternaria solani. Lesions appear first on older leaves and stems as small, circular or oval brown to black spots that gradually enlarge. Concentric rings can often be seen within the enlarged lesions. The disease is more severe during periods of warm, humid weather and defoliation can become a problem. Damage on tomato fruit will appear as large , sunken areas particularly at the calyx end or on growth cracks. The fungus overwinters on diseased plant debris. Complete removal of crop debris will reduce overwintering of fungus. Healthy, vigorous plants are less susceptible to injury from early blight. Be sure to supply adequate fertilizer and water to maintain even growth. Well spaced plants with sufficient air movement are also less susceptible to infection. Late Blight is a serious disease to potatoes and tomatoes in Atlantic Canada. It is caused by the fungus Phytophthora infestans that overwinters on infected tubers and is more of a problem during periods of humid weather during July, August, and September . Symptoms appear first as brownish-black, water-soaked blotches on the leaves. Under favorable conditions, the disease will spread rapidly through the foliage causing defoliation. Foliar symptoms are on both potatoes and tomatoes. For early maturing potatoes, late blight will not seriously affect crop development or yield, as the tubers will be developed before defoliation occurs. Later maturing varieties may require applications of a fungicide to prevent complete defoliation and to avoid being a source of contamination to neighboring commercial fields. Infection on tomato fruit appears as rough, greasy, greenish-brown patches. When taken inside to ripen , he fruit will remain firm but will turn brown and leathery. To reduce the incidence rate of late blight, begin the gardening season with clean seed potatoes. Plant only certified potatoes to prevent introductions into your garden. Do not use seed potatoes saved from the previous garden season. Introduction on tomato seed or plant tissue (from a greenhouse) is not a problem. Grow early maturing varieties and maintain vigorous growth throughout the season. Water the garden early in the day and provide adequate space between plants to ensure good air drainage. Practice good garden sanitation (remove tubers) to prevent overwintering of the disease organism. If the disease is present on the potato tops, careful harvesting can avoid infection of the tubers. To accomplish this, remove all tops from the garden area and wait two weeks before harvesting. The two-week period will kill the spores on the soil surface, which could infect the tubers at harvest time. Affected tubers will rot in storage or will act as an infection source for next year.
- Question: My cole crops often wilt during periods of hot weather and when I pull them out of the ground , the roots are huge. What causes this?
Answer: Clubroot is a serious soil-born disease of all the cole crops as well as turnips and rutabagas. It is caused by several strains of the soil-born fungus organism Plasmodiophora brassicae. The organism can remain in the soil for a number of years without host crop(s), and cannot be eradicated from infected soil, It is spread by diseased tissue or soil, and on equipment or tools which move from one site to another. Clubroot appears as small or large club like swellings on the roots. The swelling affects translocation of water and nutrients from the root zone. The plants will take on a bluish tinge and growth will be stunted. In severe infestations, the entire root system will be deformed and the foilage will turn yellow and wilt in the warm sunny weather. Clubroot infestation is greater in acid soil conditions. A soil pH maintained as close to 7 as possible with limestone can reduce the incedence of the disease. Soil conditions with a pH level of below 7 but with high concentrations of calcium and mangnesium will also control disease development. To slow down the build-up of the disease, maintain a crop rotation using crucifer crops once every 4-7 years. Several of the common weed species are also susceptible to clubroot and therefore help to maintain the presence of the organism in the soil. Try to maintain good weed control in the garden. Susceptible weeds include wild mustard, wild radish, shepard's purse, worm seed mustard and yellow rocket. Do not put infected tissue in the compost pile.
- Question: My seedlings often rot just after emerging from the seed bed. What causes this?
Answer: Damping off is a soil-born disease problem of seedlings by the fungal organisms Rhizoctonia, Pythium and Phytopthora. It is a problem in the greenhouse, in cold frames, and may appear if unsterilized garden soil or unsterilized flats or tools are used for seedling production. The fungi attack the seedlings before they emerge causing death. Seedlings can also be attacked at the soil surface after emergence. Damage appears as sunken areas on the stem at the soil line. Plants usually topple over and die. Plants can survive initial attack but will carry a scar. Affected plants will not thrive and should be discarded. Wet soil conditions promote disease development. Water lightly and only as frequently as needed. Sow seeds thinly and cover lightly with soil. Thin, thickly planted seedlings after emergence to prevent crowding. Provide good air circulation and fertilize transplants to promote good growth. The disease is most serious early in the season during periods of cool, damp weather conditions. Use sterilized mixes availible from garden centers. If garden soil is used in the mix, sterilize it in the oven. Place shallow layers of soil in metal containers in the oven for 1 hour at a temperature of 82°C. Sterilize planting containers with a solution of 1 part, (6% bleach) in 9 parts water. Rinse containers after treatment. Preventitive soil drenches are availible commercially and can be used after seeding or after emergence.
Government of New Brunswick