Diseases and pests:Spinach

1.  Athracnose Fungi Colletotrichum spp.

Symptoms: small water-soaked spots on leaves which enlarge and turn tan or brown in color with a papery texture; if infection is severe, lesions may coalesce and cause severe blighting.This disease emergence is favored by very wet weather; spores are spread by splashing water

Management

Use only plant seed from disease-free plants; avoid sprinkler or overhead irrigation where possible, watering plants from the base to reduce leaf wetness. Copper fungicides are sometimes used in the case of an epidemic but are largely ineffective at controlling the disease

2. (Aphids, Peach aphid, Potato aphid) Insects Myzus persicae Macrosiphon euphorbiae

Symptoms:         

• Small soft bodied insects on underside of leaves and/or stems of plant;
• Usually green or yellow in color, but may be pink, brown, red or black depending on species and host plant;
• If aphid infestation is heavy, it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots;
• Aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants

Management

• If aphid population is limited to just a few leaves or shoots, then the infestation can be pruned out to provide control;
• Check transplants for aphids before planting;
• Use tolerant varieties if available;
• Reflective mulches such as silver colored plastic can deter aphids from feeding on plants;
• Sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves;
• Insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation;
• Insecticidal soaps or oils such as neem or canola oil are usually the best method of control;
• Always check the labels of the products for specific usage guidelines prior to use.

3. Armyworms (Beet armyworm, Western striped armyworm) Insect Spodoptera exigua Spodoptera praefica

 

Symptoms

• Triangular, or closely grouped circular to irregularly shaped holes in foliage;
• Heavy feeding by young larvae leads to skeletonized leaves;
• Shallow, dry wounds on fruit; egg clusters of 50-150 eggs may be present on the leaves;
• Egg clusters are covered in a whitish scale which gives the cluster a cottony or fuzzy appearance;
• Young larvae are pale green to yellow in color while older larvae are generally darker green with a dark and light line running along the side of their body and a pink or yellow underside.

Management

• Organic methods of controlling armyworms include biological control by natural enemies which parasitize the larvae and the application of Bacillus thuringiensis;
• There are chemicals available for commercial control but many that are available for the home garden do not provide adequate control of the larvae.

4. Damping-off & Root rot Fungus Fusarium oxysporumnRhizoctonia solani Pythium spp.

Symptoms

• Poor germination rate of seeds;
• Death of newly emerged seedlings;
• Stunted, yellow plants, particularly lower leaves;
• Poor growth, wilting and collapse of older plants;
• Roots may be water-soaked and discolored brown or black;
• Necrotic lesions may girdle tap roots.

Management

• Plant spinach in well draining soils;
• Carefully manage irrigation to avoid saturating soil;
• Use seed that has been treated with fungicide;
• Avoid planting spinach successively in the same location.

5. Downy mildew (Blue mold) Fungus Peronospora farinosa

Symptoms

• Initial symptoms of the disease are yellow spots on cotyledons and leaves which enlarge over time and become tan in color with a dry texture;
• Purple fungal growth is present on the underside of leaves;
• Severe infestations can result in curled and distorted leaves.

Management

• Plant varieties of spinach which are resistant to the disease;
• Application of appropriate fungicides can help to protect the plant if applied before infection begins.

6. Fusarium wilt Fungus Fusarium oxysporum

Symptoms

• Yellowing of older leaves;
• Plants reaching maturity early; premature death of plants;
• Reduced seed production or death of plant before seed production takes place;
• Vascular system of older plants may have a dark discoloration;
• Seedlings may develop symptoms similar to damping off where cotyledons wilt and seedling dies;
• Black lesions may be present on roots.

Management

• Avoid planting spinach in soils known to be infested with Fusarium or where spinach has been planted the previous year;
• Planting early can help protect the seedlings from the disease due to lower soil temperatures which are less favorable to the pathogen;
• Avoid water stress to plants during flowering and seed set.

7. Mosaic and other viruses: Cucumber mosaic virus (CMV) Beet curly top virus (BCTV), Tobacco rattle virus (TRV), Tomato spotted wilt virus (TSWV)

Symptoms

• Chlorotic leaves which may have necrotic spots, mosaic patterns or ringspots;
• Leaves may be puckered and overall growth of plant is poor and stunted.

These viral diseases are transmitted by various insects such as aphids and thrips; Tobacco rattle virus is transmitted by nematodes in the soil and is not a common disease of spinach.

Management

• Practice good weed management around plants;
• Insecticide applications are generally not effective at preventing the disease but can prevent secondary spread to neighboring fields.

8. Spinach crown mite Arachnid Rhizoglyphus spp.

Symptoms

• Leaves deformed;
• Small holes in newly expanding leaves;
• Mites are tiny and transparent, living deep in the crown of the spinach plant;
• Damage can be done to newly emerged seedlings or to older plants.

Management

• Destroy crop debris immediately after harvest;
• Application of appropriate acaricide may be required if mites are damaging and weather conditions are cool and wet.

9. White rust Fungus Albugo occidentalis

Symptoms

• Yellow spots on upper side of leaves;
• Clusters of white, blister-like pustules on underside of leaves which may spread to upper leaf surfaces in advanced stages of infection;
• Infected plants show a loss of vigor and collapse if conditions are favorable to rapid disease development.

Management

• Some spinach varieties are more tolerant of the disease than others;
• Where protective fungicide applications are used, appropriate cultural control methods should also be utilized to reduce the risk of the pathogen developing tolerance to fungicide.

Symptoms

• Death of seedlings;
• Reduced stand; girdled stems and white heads;
• Wireworm larvae can be found in soil when dug round the stem;
• Larvae are yellow-brown,
• Thin worms with shiny skin.

Management

• If wireworms are known to be present in soil fallow field during summer and till frequently to reduce numbers;
• Rotate to non-host crop where possible;
• Avoid planting susceptible crops after a wireworm infestation on cereals without either fallowing of applying appropriate pesticide.

Spinach Leaf Miners (Pegomya hyoscyami) : leaf miners are tiny (6.5 mm) flies that lay their eggs on the undersides of spinach leaves.

The larvae hatch and burrow into the leaf, carving out tunnels and pockets the size of a quarter. The leaf cuticles protect them from parasitoid wasps and most garden insect predators.

Growing spinach where leaf miners are prevalent requires careful monitoring and quick action to prevent wider outbreaks later in the season. Mechanical controls work best with leaf miners.