Control of Pests and Diseases:
Pests and their Control
Cutworm, Aphids, and Mites are the few insects that attack celery in the Philippines.
1. Aphids, Aphis sp. These are small greenish insects, which are either winged or wingless. They reproduce every rapidly. The insects sucks the sap from the leaves causing curling, distortion and stunting of the plant.
Control – Diazinon and Malathion at concentrations recommended by the
manufactures are examples of effective insecticides.
2. Cutworms, Prodenia litura Fabricius. The larva of the insect is a brown worm about 5 cm long. the adult is dark pale-brown and its outer wings have transverse light brown bands. It is about 2 cm. long. The eggs are laid on the lower surface of the leaves in a mass of several hundreds and covered with matted hairs. During the day, the worms hide in the soil where they pupate. At night they come out to feed on succulent leaves and stems.
Control- The soil surface along the plant row can be treated chlorinated hydrocarbons such as Aldrin, Dieldrin, etc. at concentrations recommended by the manufacture.
3. Mites, Tetranychus truncatus Ebara. These are tiny pests difficult to see with the naked eye. They cause stippling and wattling of leaves.
Control – spray with either Tedion V-8, Diazinon, Kelthane or Chlorobezylate at concentrations recommended by the manufactures.
Diseases and their Control:
Celery is susceptible to several diseases, which are of real concern to the producer of this market crop.
1. Blight – There are three distinct blights infecting celery, but since they are all controlled by the same means, it is well to discuss them together. Late blight (Septoria apii) is characterized by small, brown, circular lesions on the leaves and stems. Black fruiting bodies of the fungus later appear in these areas. In the case of early blight Ceriopora apii, dead, ashen-gray velvety areas develop in the foliage. The bacteria ( Bacterium apii) produce lesions that are more reddish brown that those cause by late blight, in addition to a yellow halo. No black fruiting bodies are to be seen in celery infested by bacterial blight. Plants can affected by these diseases at any time during their life span.
Control – control by cultural methods and fungicide sprays is similar for each of the blights mentioned. The organism causing both late and early blight can survive on plant refuse in the soil so two to three rotations are desirable. These fungi can also survive in the seed.
Two to three year old seeds are recommended for planting because at this stage the fungi are no longer viable. New seeds can be soaked in hot water at a temperature of 48 degree C for 30 minutes to kill the seedborne fungi. Then the seeds are dried and treated with Thiram dust
Spray application should start in the seedbed and repeated every 7 to 10 days until harvested. Dithane, Zineb, and Nabam plus Zinc sulfate are effective materials. Label directions should be followed religiously.
2. Damping-off of seedlings – The most common soil-borne organisms causing this disease are: Pythium debaryanum Hesse, Rhizoctonia solani Khun and Scelrotium rolfs Sacc-all fungi. Seeds infected with the disease may either decay before they germinate; sprouts are killed before they reach the soil surface, or seedlings may develop lesions near the soil level and fall over.
Control – Disinfecting of the soil in the seedbed or seedboxes is usually desirable. Watering the beds in the day so that the soil surface will be dry at night will help reduce infection.
Seeds can be placed in the cloth sack and soaked until moistened in a solution of 1 oz. of Calomel (mercury chloride) in 1 gal. of water. Another method is to coat the seed thoroughly with either Captan, Chlonil or Thiram dust at the rate recommended by the manufacturer. Such treatment should be used on hot water-treated seed.
3. Bacterial Rot – is caused by a bacterium, Erwinia carotovora Holland. Small lesions appear on the fleshy petioles and rapidly enlarge. Finally, a soft, mushy rot develops.
There is no specific stage of maturity at which celery must be harvested. If cut too early in the season, the yield would greatly be reduced. However, celery can be cut when a little over-mature, but not too late as to allow the petioles from becoming pithy, in which case, they lose their high quality.
In harvesting celery, the plants are cut below the soil surface with a large knife before leaving the petioles attached at the base. Tiller or suckers, short and prongy outside the petiole, and diseased or injured leaves are cut off before they are washed and packed in convenient containers.