A Complete Guide to Identifying and Controlling Flower Pests

Types of Pests  

According to the parts of the flower they damage and the way they do it, pests can be divided into the following categories.  

1. Leaf-chewing pests:

These pests take big bites out of flower leaves when they feed, causing the leaves to become damaged; in severe cases the leaves can be eaten completely bare.

Common pests of this kind include the yellow slug moth and scarab beetles, as well as harmful animals such as snails and woodlice, which gnaw on leaves and tender shoots.  

2. Piercing-sucking pests:

The mouthparts of these pests are like needles, able to pierce into the tissues of flower plants (leaves or tender tips) and suck out the plant's nutrients, causing leaves to dry up and drop off; affected leaves lose their green colour and turn white or brown.

These pests are relatively small and extremely varied in kind, and are sometimes hard to spot. Common ones include aphids, scale insects, whiteflies, thrips and spider mites. Some of these pests secrete honeydew, and some secrete a waxy substance. They not only contaminate flower leaves and branches, but also very easily lead to sooty mould, so that the leaves and branches appear to be covered with a thick layer of coal dust.

Among these pests, the mites can spin silk and form webs; in severe cases the webs can stick leaves and branches together, at which point they are very easy to spot, and this is also a period when the pest infestation is quite severe. 

 

3. Boring pests:

These pests bore into the branches and stems of flowers and feed inside, hollowing out the stems and branches and killing them.

Examples include the chrysanthemum longhorn beetle, the dahlia stem borer moth and the rose stem sawfly. Some bore into leaves to do damage, and the tunnelled passages can be seen in the leaves, causing the leaves to dry up and die.  

4. Soil-dwelling pests:

These pests live their whole lives in the shallow and surface layers of the soil.

Where flowers are damaged, tunnelled passages or death can often be seen in the leaves, as with cutworms, wireworms and mole crickets.  

Inspection and Identification  

1. Check for insect droppings:

Check whether there are insect droppings on the ground around the flower plants and on the branches. For pests that bore into branches and trunks, check whether droppings and wood shavings have fallen to the ground from the frass holes. Longhorn beetles excrete droppings and wood shavings that are mostly thread-like; those of wood borers are granular and stick together in strings.

 

2. Check for excreta and secretions:

Check the branches, leaves and other parts of the flower plants for oily smudges; when these substances are found, they are generally produced by pests that secrete honeydew or wax, mainly piercing-sucking pests such as aphids, scale insects and whiteflies.  

3. Check for eggs:

Large eggs and egg masses can be seen with the naked eye, while tiny eggs can be seen with a magnifying glass. Eggs are generally laid on branches, leaves, leaf axils and other places; for example, red spider mite eggs are mostly laid on the underside of leaves; tent caterpillar eggs are laid on branches; aphid eggs are mostly in the leaf axils; and locust eggs are found in the soil.

Because different pests have different living habits and lay their eggs in different places, searching in their egg-laying sites makes it possible to further identify the pest species and the damage, so as to allow early control.

4. Tap branches to check:

For some pests that fly up when startled, tapping or shaking the branches and leaves will reveal them. Red spider mites and similar pests are small and hard to make out with the naked eye, so a white sheet of paper can be placed in a representative spot among the branches and leaves, which are then tapped; whether red spider mites are present can be judged by whether they appear on the white paper.

5. Check the damage symptoms:

Check whether the leaves and branches of the flower plants have any gnawed spots, such as holes, notches or net-like patterns; or curled leaves, or foreign growths on the branches, withered tips or dead branches, and so on.

 

6. Check for pests in the soil:

First check whether the soil surface looks abnormal. For example, when mole crickets move about on the surface soil, raised trails are left on the soil surface. Some adult scarab beetles lurk beneath the surface soil around the roots and stems of flowers, and can be found by turning over the surface soil.

Control Methods  

Wood ash soaking method:

Use 500g of wood ash, mix with 2.5kg of water, soak for a full day and night, filter out the impurities, then spray the affected plants with the clear filtrate; this can effectively kill aphids.

Vinegar leaf-wiping method:

Use 50ml of table vinegar (rice vinegar), dip a cotton ball in the vinegar, then gently wipe the leaves of the flower plants with the vinegar-soaked cotton ball; this can both wipe away and kill scale insects and restore the green shine to leaves previously damaged by scale insects.

Alcohol leaf-wiping method:

Gently and repeatedly wipe the leaf surfaces damaged by scale insects with alcohol, and the scale insects can be removed; even larvae that cannot be seen with the naked eye can be completely killed.

Iodine tincture application method:

If the main trunk of a woody flower plant rots, first scrape away all the rotted part down to the xylem, then apply iodine tincture, and apply it again after 7-10 days; not only can it be completely cured, but over time the main trunk develops prominent burls, which increasingly bring out an aged, striking look with a distinctive charm.

Baking soda spray method:

Finely spray affected plants with a 0.1% baking soda (NaHCO3) solution; the control rate for powdery mildew on flowers such as roses, chrysanthemums, garden balsam, cotton rose and cineraria can reach more than 80%.

Washing powder solution spraying method:

The specific preparation method is to mix 1g of washing powder with 100-180g of water until even. Spray once a week, and after 2-3 consecutive treatments the damage from scale insects and aphids can be controlled. Note, however, that a neutral washing powder should be chosen; if burning appears on tender leaves, promptly spray some clean water to rinse off the residual solution.

Camphor ball burying method:

Sew 2 camphor balls into a small cloth bag and bury it at the roots of the flower plants; this can prevent longhorn beetles and other trunk-boring pests.

Essential balm spray method:

Spray a 600-800 times diluted solution of essential balm; this can control aphids, red spider mites, scale insect nymphs and moth and butterfly larvae, with a pest control effect of 90%.

Sugar-vinegar solution spraying method:

Spray potted flowers with a mixture of 2g of sugar, 3g of vinegar and 95g of clean water; this can kill many kinds of pests and pathogens, and also has a fairly good effect on the chlorosis of flowers such as camellias and rhododendrons caused by iron deficiency.