Plant Health Problems
Diseases caused by Fungi:
Leaf spot, Cercospora beticola.
Small, circular, tan spots appear scattered over the leaves. The spots have a purple border. This fungus disease is also found on chard and mangels.
Since the disease can be carried in the seed, the use of fungicide-treated seed may be beneficial.
Diseases caused by Bacteria:
Scab, Streptomyces scabies.
Scab is caused by a soilborne bacterium that infects the roots causing corky spots. Yield is rarely reduced but damaged roots may become unmarketable. Scab usually appears in heavily-limed soils. See Potato and Common Scab for a more detailed discussion of this disease.
The bean aphid and the green peach aphid feed on beets. See Aphid fact sheet.
Blister beetles, Family Meloidae.
Several species of large, active, slender, soft-bodied beetles may occasionally feed on the greens. They are usually dark colored and may have thin white lines on their wingcovers. The larvae live in the soil where they feed entirely upon grasshopper eggs. Control is not usually necessary.
Several species of flea beetles including the potato flea beetle, Epitrix cucumeris, the palestriped flea beetle, Systena blanda, the redheaded flea beetle, Systena frontalis, and the smartweed flea beetle, Systena hudsonias, may feed on beets. Young plants may be damaged though older plants show no injury to the feeding. Control measures are rarely necessary. See Flea beetle fact sheet.
Garden springtail, Bourletiella hortensis.
Tiny yellow-spotted purple insects eat holes in the leaves of seedlings. These insects have no wings but are equipped with forked, tail-like appendages by means of which they project themselves into the air. They are usually found only on small plants near the surface of the soil. Control is not usually necessary.
Spinach leaf miner, Pegomya hyoscyami.
This leaf miner feeds on beets and spinach, but unless the beets are being grown for their greens, control is not usually necessary. It also infests chard and several common weeds, including nightshade, chickweed, plantain, and especially lambsquarters. There are three or four generations each season and the insect winters in the soil in the pupal stage. The adult is a gray fly about 1/4" long. It emerges in April or May and lays white cylindrical, netted eggs in clusters of from two to five on the underside of a leaf. They hatch in 4 to 6 days and the young maggots enter the tissue of the leaf where they make first thread-like mines, and then blotch mines, which may eventually involve the entire leaf. If food becomes exhausted, they migrate to other leaves. The larva, about 1/3" long, matures in a period that varies from 7 to 16 days. It then descends 2 or 3" into the soil and pupates, the flies emerging 14 to 25 days later.
Row covers can be used to keep the flies away from the plants, but the area planted must have been free of both cultivated and weed hosts in the previous year. Deep spring plowing can destroy overwintering leafminer pupae. The gardener can find and crush the eggs on the leaf and remove leaves with mines and destroy them. Malathion is among the compounds registered for control of this pest in Connecticut. Chemical control must be directed to control adults, since once the larvae are inside the leaf, this insecticide will not reach them. Consult the label for dosage rates, safety precautions, and observe the long required interval from application to when the spinach may be harvested.