Celery, Celeriac (Apium)
Plant Health Problems
Diseases caused by Fungi:
Fusarium yellows, Fusarium oxysporum f. sp. apii.
The disease first appears in the field as stunted, yellow, and wilting plants. If the plant crown and roots are sliced open with a knife, the water-conducting tubes in the plant will be discolored. The disease can lead to plant death if susceptible cultivars are grown. The fungus is soilborne and can persist in soil for long periods of time. The fungus can survive on weeds and other crop plants without exhibiting symptoms.
Two- to three-year rotation with cucurbits and onions will reduce soil inoculum. Moderately resistant plants are also available.
Root and crown rot, Rhizoctonia solani, Pythium spp.
Symptoms appear as wilting and a slow or rapid collapse of the plant. The roots can appear brown and water-soaked instead of white. A water-soaked lesion can often appear at the base of the stem.
Control can be achieved by improving water drainage in the field and using a two-year rotation with nonsusceptible plants, such as corn, to prevent the buildup of pathogenic organisms.
Early blight, Cercospora apii.
This blight is caused by a fungus and appears as large, irregular, dark-brown spots on the leaves and stems. The leaf spots are generally bounded by the veins. In severe cases, the spots grow together and kill the leaves. Early blight is caused by a fungus which may be carried in the soil or on the seed. The fungus does not live in the seed for more than two years.
When using newer seed, it may be best to disinfect it by dipping for 30 minutes in hot water (118 F). The incidence of this disease in Connecticut is rare. Control can also be achieved with the use of fungicide sprays applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are chlorothalonil, thiophanate-methyl, or copper sprays. Consult the label for dosage rates and safety precautions.
Late blight, Septoria apii.
Late blight is a common fungus disease of celery in Connecticut which appears as small, circular, tan leaf and stem spots. Usually there are small, black dots scattered across the tan spots. Gelatinous threads of spores are exuded from these dots during wet weather.
The disease is not a major problem in Connecticut and usually does not require controls. However, control can be achieved with the use of fungicide sprays applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are chlorothalonil, maneb, thiophanate-methyl, or copper sprays. Consult the label for dosage rates and safety precautions.
Diseases caused by Phytoplasmas:
Aster yellows, phytoplasma.
Celery that has aster yellows has an abnormal number of leaves. The leaves are yellow, twisted, and stunted. The roots remain slender and have an abnormal number of fine hairy roots. Aster yellows of celery is caused by a bacterium-like organism called a phytoplasma which also causes the disease on asters, carrots, and lettuce. The phytoplasma is carried by leaf hoppers.
To keep down the amount of disease, growers should control leafhoppers with insecticides and avoid planting carrots near asters.
Diseases caused by Nematodes:
Pin nematodes, Pratylenchus hamatus.
The pin nematodes are too small to see with the naked eye, but they live in the soil and feed on the roots of celery and other plants. They stick their stylets into the plant roots and suck the food from the plant tissue. Although the nematodes are individually very small, they may be present in such numbers that they will cause stunting and yellowing of celery and other crops.
Rotation with nonsusceptible plants, such as corn, can reduce the number of pin nematodes in the soil. Growing celery in a new area will also control the disease. Care should be taken to avoid carrying any soil from the old site to the new site.
Root-knot nematodes, Meloidogyne hapla.
Infected plants are stunted and sickly, with knots on their small, feeding roots. This disease is caused by nematodes which can persist in the soil for years.
Rotation with nonsusceptible plants, such as corn, can reduce the number of nematodes in the soil. Growing celery in a new area will also control the disease. Care should be taken to avoid carrying any soil from the old site to the new site.
Diseases caused by Physiological/Environmental Factors:
Boron deficiency or cracked stem.
Celery deficient in boron has many parallel cracks across their stems. Later the tissue between the cracks curls up in strips. The leaves of deficient plants may show areas of brownish discoloration.
Applying a balanced fertilizer that is supplemented with micronutrients can reduce the incidence of cracked stem.
Heart rot, calcium deficiency.
Celery plants grown in hot weather can frequently develop a calcium deficiency in the center of the crown causing it to not develop. Soft-rotting bacteria frequently enter and cause a wet slimy rot.
Control is difficult to achieve, but efforts to water the plant more regularly and use mulching can reduce the incidence of heart rot.
Most insects on celery also feed on carrot. See Carrot for information on additional insects.
Celery leaftier, Udea rubigalis.
Although this small greenish-white striped caterpillar may occasionally feed on leaves, it is not a serious pest and control is rarely needed.
Parsnip webworm, Depressaria pastinacella.
When parsnip and celery are grown for seed, some injury may be caused by this caterpillar which webs together and feeds upon the unfolding blossom heads. The caterpillar is slightly more than 1/2" long when full grown, greenish yellow with black head and legs, and covered with small black warts. There is one generation a year and the moths live through the winter. When nearly mature, the caterpillars leave the web and burrow inside the flower stems where they pupate. Control is not usually necessary.
Tarnished plant bug,
This bug injures many different kinds of plants by sucking sap from the tender leaves and shoots. On celery the injury shows as darkened sunken areas about 1/4" in diameter on the leaves and shoots near the top of the plants. Feeding in the heart can also cause the death of young leaves, which may then be degraded by soft rot. The tarnished plant bug is a mottled brownish bug about 1/5" long that hibernates in protected places. The eggs are inserted in the tender tissues of plant stems, leaves, and buds, and the young bugs or nymphs are yellowish green and pass through five nympal stages before becoming adult. The adults are good fliers, and often move into vegetable crops from feeding on hayfields or weeds. Nymphs are not usually found on celery. A recently introduced parasitoid of the tarnished plant bug, Peristenus digoneutis, attacks the nymphs of the tarnished plant bug on alfalfa and may help to reduce populations moving into vegetable crops. Carbaryl is registered for control of this pest in Connecticut, but observe the long interval required between insecticide treatment and celery harvest. Also consult the label for dosage rates and safety precautions.
Twospotted spider mite, Tetranychus urticae.
This mite, which is about 1/16" long when mature, lives on the underside of leaves where it sucks plant sap. The leaves of infested plants have a sickly appearance, with yellow or reddish-brown blotches. Webbing may be visible in heavy infestations. Injury is most severe in hot, dry weather. Natural enemies normally regulate the population as long as pesticide use is avoided, so control is not usually necessary.