Tuber, Corm and Bulb Troubles

Many plants are raised from bulbs, corms, rhizomes and tubers. These fleshy organs are at risk throughout their life cycle. They may be attacked in the soil by swift moth caterpillar, bulb aphid, narcissus fly and eelworm and by animals searching for food. Root pests such as wireworm, chafer grub and vine weevil will also attack bulbs and corms.


Dahlia tubers can be destroyed in store by fungal rots. To prevent this from happening, stand the tubers upside down after lifting and allow them to dry. Clean off all soil. Spray thoroughly with benomyl; leave them to dry before storing in boxes in a dry frost-free place. Inspect tubers from time to time; cut away any diseased parts.


A destructive disease of Flag Iris, especially in badly drained soil. Leaf tips yellow and wither; later the fan of leaves collapses. A yellowish slimy rot affects the rhizomes. Plants can be saved if the soft diseased areas on the rhizome are cut away as soon as they are seen and the rhizome and soil are treated with a Copper dust.


Several serious storage rots affect Tulips and Daffodils. Narcissus smoulder causes the bulbs to decay, small fungal growths appearing on the outer scales. Basal rot begins at the base of the bulbs of Daffodils and Lilies, the brown rot spreading upwards through the inner scales. Tulip fire is the most serious disease of this bulb; small fungal growths appear on outer scales and both shoots and flowers are damaged. If rotting has occurred in the past, immerse bulbs in benomyl shortly after lifting. Repeat dip shortly before planting. Remove rotten bulbs from store.


Affected bulbs of Daffodil, Tulip, Hyacinth etc are soft and rotten. Tell-tale dark rings can be seen in a cut bulb. Daffodil leaves are pale, twisted and bear characteristic small yellow swellings on the surface. Throw away all soft bulbs. Do not plant bulbous plants on affected land for at least 3 years.


Several serious storage rots occur on Crocus and Gladiolus corms. Dry rot causes many black spots to appear on the corm, which later merge and the tissue completely decays. With hard rot the spots are brown and the affected corm becomes shrivelled. The spots of scab are round, brown and shiny. Core rot is quite different from the other corm diseases – it starts at the central core of Gladiolus corms and then spreads outwards as a moist rot. If rotting has occurred inthepast, immerse cormsinbenomylshortlyafterlifting. Repeat dip shortly before planting. Remove rotten corms from store.


These soil-living caterpillars attack Gladiolus corms, Iris rhizomes and all types of bulbs. Unlike cutworms they move backwards when disturbed. If swift moth is known to be a serious problem, rake in Bromophos before planting. Otherwise keep the pest under control by hoeing regularly.


Colonies of greenfly may develop on Tulip and Lily bulbs and on Crocus and Gladiolus corms in store, sheltering and feeding under the outer scales. Young growth is severely affected when infested bulbs are planted. Rub off aphids before planting; if the aphids are numerous sprinkle bulbs with Gamma HCH dust.


A common pest of the vegetable garden which can be damaging to flowers belonging to the Pea family (Sweet Pea, Lupin etc). Seedlings are most at risk, and should be protected by sprayingwith Long-last. HexylorFenitrothion if the characteristic U-shaped notches appear on the leaves. Leaves of older plants may be damaged, but spraying here is not usually necessary.


Many different leaf-eating caterpillars attack annuals and perennials in the flower garden. Some are uncommon; a few such as the angle shades moth and the cabbage white butterfly can be serious pests. Pick off the caterpillars if this is practical – if damage is widespread spray with a persistent insecticide such as Long-last or Fenitrothion.


Smooth caterpillar, about 2 in. long, which can be a serious nuisance on Dahlia, Gladiolus and many perennials.


An abundant pest in shady town gardens, hiding under stones or leaves during the day and devouring young leaves of a wide range of flowering plants during the night. Woodlice favour plants which have already been damaged by a previous pest. Control is not easy – do not leave rubbish in the garden and scatter Slug Gard around the plants.


Holes in Leaves

Holes and tears in tender leaves are sometimes caused by frost or severe weather, but the usual culprit is an insect pest. Seedlings, small plants and the lower leaves of tall perennials can all be seriously damaged by pests such as slugs, snails, woodlice and vine weevils which feed on the foliage at night and hide under stones, debris etc during the day. Above-ground pests can attack leaves growing at all levels – capsid bugs produce small, brown-edged holes and caterpillars form large holes or even completely skeletonise the foliage. Many types of caterpillar may be found – the angle shades moth attacks the widest range of plants and the vapourer moth can be a nuisance in town gardens. Note that these garden caterpillars are the larval stage of moths rather than butterflies – the abundant cabbage white is the only exception.


Smooth caterpillar, about VA in. long, which attacks several annuals and perennials. Leaves may be skeletonised.


Serious pests, especially on Tulip, Iris, Delphinium, annuals and rock plants. Irregular holes are formed and tell-tale slime trails can be seen. Damage is worst on a shady, poorly drained site. These pests generally hide under garden rubbish during the day, so keeping the area clean and cultivated is the first control measure. Scatter Slug Gard or Slug Pellets around damaged plants.

Tiny black or black and yellow beetles attack seedlings of the Crucifer family (Stock, Wall-flower, Aubrietia, Alyssum etc). Numerous, small round holes appear in the leaves. Growth is slowed down and seedlings may be killed. The beetles jump when disturbed. Spray the young plants with Long-last, Hexyl or Liquid Derris as soon as the first signs of damage are noticed.

Slightly hairy caterpillar, about Ivi in. long, which attacks several annuals and perennials. Leaves may be skeletonised.


Colourful caterpillar.about 1 in. long, which feeds on the leaves of many perennials from May until August.


A familiar pest which attacks Chrysanthemums, Dahlias and several other garden plants during summer and autumn. Males have hooked pincers, females bear straight pincers. They are night feeders, hiding in the petals during the day. To control this pest, shake the stems and then spray plants and ground thoroughly with Long-last or Hexyl.


These little green bugs are a serious pest of Dahlias. Chrysanthemums, Salvias and other flowering plants may also be attacked. At first the leaves are spotted; as the foliage enlarges small ragged holes with brown edges are formed. The leaves are distorted and puckered. Spray both the plants and ground with Long-last or Fenitrothion.

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