Leaf & Stem Troubles

Aphids and powdery mildew are serious problems in a dry summer, and grey mould can be destructive when the weather is wet. Starvation leads to poor leaf and stem development, and traces of lawn weedkiller can lead to severe distortion.

DAMPING OFF

The damping off fungi attack the roots and stem bases of seedlings. Shrinkage and rot occurs at ground level and the plants topple over. The golden rules are to sow thinly and never overwater. Ensure adequate ventilation under glass. Remove collapsed seedlings immediately; water remainder with Cheshunt Compound.

LEAFHOPPER

Pale mottled patches or flecks appear on the leaves – common on Pelargonium and Primula during the summer months. Small yellowish insects or their empty white skins will be found on the underside. Direct damage is usually slight but they can transmit viruses. Spray with Long-last or Bio Sprayday.

CHRYSANTHEMUM EELWORM

The leaves develop brown areas between the veins; the plants may be killed if the infestation is severe. Aster and Paeony as well as Chrysanthemum may be attacked. The closely-related leaf blotch eelworm produces similar symptoms on Begoniaand ferns. Pickoff and burn affected leaves; destroy severely infested plants.

STEM ROT

Several types of stem rot attack garden flowers – all are serious. Part or all of the stem decays and the leaves wilt. Sclerotinia disease is a common cause in herbaceous border plants – Sunflower, Campanula, Chrysanthemum etc. Hard black bodies occur in the pith. There is no cure – lift badly diseased plants and burn.

COLD DAMAGE

A sudden cold snap in spring can affect developing leaves and leaf buds by destroying chlorophyll. The affected leaf, when it expands, may be yellow-edged (Anemone, Sweet Pea etc), almost white (many bedding plants) or white-banded (Daffodils). Pick off badly affected leaves; spray with Fillip to speed recovery.

FROGHOPPER

The frothy white masses (’cuckoo spit’) which occur on the stems of Geum.Solidago, Chrysanthemum, and many other flowering plants, are familiar to everyone. Less well known is the cause – pinkish 0.5 in. froghoppers which suck the sap and distort young growth. Hose with water, then spray with Long-last or Hexyl.

LEAFY GALL

A mass of shortened shoots with thickened, distorted leaves sometimes develops at the base of the plant. This disease is spread by tools or by taking cuttings from diseased stock, so affected plants should be destroyed and not used for propagation. Susceptible plants are Sweet Pea, Chrysanthemum, Dahlia and Pelargonium.

PHLOX EELWORM

The young leaves of infested plants are strap-like and die off prematurely. Older leaves are distorted. Several perennials, such as Phlox, Gypsophila and Aubrietia may be attacked. The crowns of Polyanthus are killed. Dig up and burn infested specimens; do not replant with susceptible perennials for at least 3 years.

FOOT ROT

The tell-tale sign is the blackening and rotting of the base of the stem. The name depends on the plant affected – geranium blackleg, pansy sickness, campanula crown rot etc. Use sterile compost in seed boxes or pots. Avoid waterlogging. Destroy infected plants and water remainder with Cheshunt Compound or Dithane.

TULIP FIRE

A serious disease of Tulips, causing scorched areas on the leaves and spots on the flowers. Young shoots may become covered with a grey, velvety mould. Rotting of bulbs occurs . Cut off diseased emerging shoots below ground level; spray the remaining plants with Dithane. Repeat at 14-day intervals. M

Several species of aphids infest annual and perennial flowers in warm, settled weather. The commonest are the black bean aphid and the peach-potato aphid. Young growth is distorted and weakened; leaves are covered with sticky honeydew which later becomes covered with sooty mould. Keep plants well-watered in dry weather. Spray with Long-last, Bio Sprayday, Malathion or Liquid Derris as soon as colonies start to appear.

Long winding tunnels are eaten in the leaf tissue by small grubs. At first the tunnels appear white, later they turn brown. Chry-santhemum foliage is commonly attacked in this way. The carnation fly behaves rather differently, producing blotches on the leaves and sometimes killing the plant. Pick and destroy mined leaves. Spray with Hexyl.

Leaves and shoots sometimes wilt badly even though the soil is moist. If the plant is an Antirrhinum, Aster, Sweet Pea, Carnation, Chrysanthemum, Lupin or Poppy then the likely cause is a soil-borne fungus. Tissue inside stem will probably be stained brown. There is no cure. Remove diseased plants – do not grow susceptible plants on the same spot.

RED SPIDER MITE

If leaves develop an unhealthy bronze colour, look for tiny spider-like mites on the underside of the leaves. The presence of fine silky webbing is atell-tale sign. In hot settled weather spraying may be necessary – use Long-last or Liquid Derris.

A destructive disease in wet seasons. Fluffy grey mould appears on the leaves; with many bedding plants (Godetia, Clarkia, Petunia, Zinnia etc) stems are attacked. Remove mouldy leaves and badly infected plants immediately. Spray with a systemic fungicide.

POWDERY MILDEW

The main symptom is a white mealy growth on the leaf surface. It is encouraged by overcrowding and lack of soil moisture. This is the disease commonly seen on Michaelmas Daisy. Delphinium and Chrysanthemum. Spray with a systemic fungicide at the first sign of disease and again 1 week later. Repeat if disease reappears.

Look for the tell-tale sign of coloured swell-ings on the leaves and stems. These raised spots may be yellow, orange or brown. It is a common disease of Antirrhinum, Hollyhock, Pelargonium. Carnation, Chrysanthemum and Sweet William. Pick off and burn diseased leaves; spray with Dithane every 2 weeks.

DOWNY MILDEW

Less likely to be trouble-some in the flower garden than powdery mildew, al-though Antirrhinum, Sweet Pea, Poppy and Wallflower are often affected in damp weather. Upper leaf surface shows yellow or dull patches; greyish mould growth occurs below. Plants are crippled by a severe attack. Spray with Dithane at the first sign of disease; repeat at 14-day intervals.

Viruses may be carried by insects, tools or fingers. There are many different symptoms of virus infection – leaves may be yellow, covered with yellow spots or patches (mosaic), crinkled and distorted or white-veined. Stems may be covered with brown stripes (streak) or stunted and distorted. There is no cure; if you are sure of your diagnosis, lift and burn. Buy healthy stock; keep aphids under control.

Leaf spot is a family name for a wide group of diseases which appear on many types of flowering plants. Leaf spot (round or oval coloured spots) is an important disease of Pansy, Phlox, Polyanthus, Poppy, Iris and Sweet William. Ring spot (dark concentric rings of spores) is common on Carnation, and leaf blotch (irregular-shaped spots) affects Delphinium. Pick off diseased leaves. Spray with a Copper spray or Dithane, but control may be difficult.

Sorry, comments are closed for this post.