Green peach aphid (Myzus persicae)

It is a very detrimental insect to spinach. It can transmit diseases that can wipe out large portions of the crop. Aphids and leafminers cause the most serious damage on the crop (University of Georgia). The aphid is pale yellowish in colour and small. It lives mainly on the underside of leaves and therefore hard to control.

Downy mildew (Peronospora spinaciae / Peronospora farinosa)

This fungus is distributed worldwide. It causes leaf spotting that spoils the quality and appearance. Leaf spots begin as indefinite yellowish areas on the upper leaf surface. A mat of grey to violet mould develops on the corresponding lower surface. With time under cool, wet conditions, the spots enlarge until the whole leaf turns black and dies. The fungus increases profusely in high humidity. The spores can over-season in mild climates in living spinach, in seeds and in the soil.

Bacterial soft rot (Erwinia carotovora)

It is one of the most important diseases. Its symptoms include water soaked tissue and muddy-green or greasy appearance of leaves. Rapid decay occurs and the tissue becomes wet and mushy. This bacterium is found in the soil and in plant debris. It can enter into the plant through mechanical injury, insect injury, disease lesions and other skin punctures.

Fusarium wilt (Fusarium oxysporum f. sp. spinaciae)

It is a wilt that is caused by a fungus. Plants can be affected any time after the three-leaf stage. Foliage loses its green luster, gradually wilts and turns yellow, beginning with the oldest leaves. The fungus is soil-borne and seed-borne. It commonly occurs where temperatures are fairly high. It can live in the soil indefinitely and rotation is not effective in its control.

White rust (Albugo occidentalis)

It is a fungus that causes white blister-like pustules on the underside of leaves. They are filled with white spores and the surrounding tissue turns brown and dies. The fungus favours clear, warm, and dry days with cool nights.

Cucumber Mosaic Virus (CMV)

It is transmitted by the green peach aphids. Symptoms begin as a mottling of the younger inner leaves, which later change to a yellow colour. The symptoms gradually appear on outer leaves, which also change to yellow. The affected leaves curl and wrinkles. Severely affected leaves die. If a plant is affected at the seedling stage, its growth is stunted. The Dwarfing, yellowing, corrugation and leaf death are conspicuous symptoms of the disease different from other diseases attacking spinach.

Intensity of the virus increases under long days and intense light. This virus affects, in addition to spinach, a wider group of vegetables, flowers, weeds and ornamentals than any other virus. At least 34 plant families are included as hosts.