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Pests & Diseases

Disease & Plant Health

Healthy plants have firm leaves, well-formed flowers and fruit, and well-developed root systems.

Unhealthy plants show damage to leaves, stems, roots, flowers or fruit.


A pest is an animal that damages plants.


Pests can kill plants, slow their growth and damage stems, leaves, flowers and fruit. A host is a plant on which the pest feeds. Some pests can also introduce diseases into plants.

There are two main types of plant pests: chewing and sucking.

Chewing Pests

Chewing pests tear, bite or chew parts of the plants: leaves, stems or roots.
Pests such as borer and leaf miners tunnel into stems or leaves by chewing.
Rabbits and possums are large chewing pests.

Chewing pests eat parts of plants such as roots or leaves. They include caterpillars, beetles grubs, slugs, snails, and slaters.

Caterpillar leaves holes in the centre of leaves - and can be treated with Derris Dust. 

Slugs / snails  tend to eat from the edges and can be treated with slug / snail pellets - a handful scattered around the base of the plant. Clear away any dead leaf litter around the base of the plant.

Sucking Pests

These pests have special piercing mouthparts for feeding. The mouthpart sticks into the plant, sucks sap out and pumps saliva into the leaf and stem. 

Plant tissue is digested and leaves become deformed, stunted or discoloured.  Sucking pests suck sap and can also transmit viral diseases. They include aphids, thrips, whitefly and mites.


Leaf Hopper

Leaf hoppers are plant eating insects that can damage plants and transmit disease from plant to plant.

Young leaf hoppers are known as fluffy bums

Damage usually occurs in summer & autumn and is mostly confined to mature leaves. You can usually tell you have leaf hoppers by pale yellowing of the foliage. Leaves develop typical areas of yellow speckling where leafhoppers have been sucking up plant sap. The damage caused is mostly cosmetic.

In autumn leaf hopper females lay eggs in the stems of host plants. Eggs hatch in spring. Young nymphs feed on the underside of leaves, developing through 5 growth stages before moulting as winged adult males and females. Mated females usually lay summer eggs in the veins of host plant leaves, where they are protected from some non-systemic pesticide sprays.


Most general-purpose contact insecticides containing pyrethrins will help deal with them. Make sure you spray under the leaves to catch all the leafhoppers. The adults will leap away when the spray falls near them, so repeated sprays may be needed to destroy the survivors. It is better to spray at night when less active.

With contact insecticides you'll have to ensure that all parts of the plant are covered, and several sprayings may be needed to give good control.

Spray with Insecticides on roses and ornamentals. Both kill rapidly without any leaf burn or marking. 

We recommend the use of AQUATICUS GLOW as preventative treatment once the infestation is under control.

Kiwicare also offer some great natural and BioGro® certified alternatives to deal with leaf hoppers in your garden. Organic Super Spraying Oil sprayed directly on leaf hoppers and their fluffy bum juveniles will control them. Do not spray in hot sunny conditions as burning can occur.

Aphids / Greenfly

Aphids or greenfly are small, sap sucking insects that are commonly found on buds and new leaves and stems of roses and other plants.

Aphids, sometimes referred to as greenfly, are small*, soft insects with pear-shaped bodies and long & thin with sharply bent legs. They can be coloured brown, black, yellow, pink or green. Woolly aphids look like cotton wool.

Typically aphids may cause stunted shoots, distorted leaves, wilting, honeydew and sooty mould.
Aphids survive during the cooler winter months and are usually hidden within leaf/flower buds. They multiply rapidly during warmer months in spring or summer. Aphids can be usually found in clusters on young shoots, flower buds or underneath leaves.

Aphids are sap suckers. Sap is the plant´s food, nutrient and water circulation fluid. When aphids or other sap sucking insects suck sap from a plant, the plant is weakened and there is a risk of the insect infecting the plant with disease. 

Aphids feed on a variety of plants but mainly feed on soft leaves and shoots (see also  root aphids). Because aphids attack the new buds, the resulting leaves and flowers may never open properly; remaining puckered and curled. Most damaging of all, aphids can transmit serious virus and fungal diseases from one plant to another. A particularly bad aphid infestation often leaves a sticky residue of leaking sap on the plant that will grow a sooty mould, an unattractive fungal growth.

In the photo you can see some aphids. When the mouthparts of these pests penetrate plants they suck out the sap. They can spread viruses as they move the sap from plant to plant.
Aphids also produce honeydew on which sooty mould grows.

Sooty mould on citrus leaves

Sooty mould on citrus leaves

Sooty Mould

What is sooty mould?

Sooty moulds are caused by Ascomycete fungi. They grow on the sap from plants and produce a sweet honeydew as a waste product discharged by insects like scale and aphids. The mould then expands on the honeydew. However, the mould doesn’t feed on the plant; it covers the leaf surface, blocking the light and reducing photosynthesis, vital for plant growth. 


The sooty mould forms a thick black coating on the tree's trunks, branches, and leaves. 


  • Spray with insecticide to control the sap-sucking insects

  • Spray with a fungicide to kill the mould 


  • Grow a variety of different plants to build an appropriate habitat for beneficial insects that predate on pests 

  • Create good airflow between plants 


If your plants already have an infestation you can squash them between your fingers but this might be difficult on more than a few buds. Use a Kiwicare  PLANThealth Spectrum concentrate to spray the affected parts of the plants. 

Make sure the undersides of leaves and inside curled leaves are treated.

Mix 10 ml per 1 L of clean water.
Spray foliage until run off occurs.
Spray leaves on both the upper and lower surfaces as complete coverage is required for effective control.
Apply every 10-14 days.

For a great natural and BioGro® certified alternative try Organic Super Spraying Oil to suffocate the aphids on contact but do not spray in the middle of the day as the sun can reflect onto the oil and burn the plant.

White Stuff on Flax

Often around dead leaves from around flax plants, you can find patches of white scale & fluffy stuff.


The pest that is causing the white stuff is a type of scale. If you scrape away some of the cotton-like covering and look carefully you should be able to see small white pear-shaped adult scales.
The young scales (crawlers) are even smaller and you may even see them moving around - the adults don't move - they just stay put and suck the leaf sap.
Severe scale attack can debilitate the plant and cause yellowing of leaves.

Spray with insecticidal oils like Conqueror or Clear White Oil, or systemic insecticide products like PLANT HEALTH SPECTRUM

Clear away as many of the old leaves as possible and expose the affected areas to the sun, rain and insect-eating birds. The scale numbers will naturally be reduced to the point where they'll have little adverse effect on the plant.

A disease is caused by bacteria, fungi, and viruses.


Diseases are caused by fungi, bacteria or viruses.
Disease prevents plants functioning properly and interferes with growth and development. It can be difficult to work out exactly what has caused a particular disease, as many plant diseases have similar signs.


Fungi are plants that cannot make their own food and rely on other plants or animals (dead or living).

Many fungi are beneficial, but some can damage or destroy the leaves, stems or roots of plants. They may attack and grow into and through the plant tissues as a mass of fine threads, feeding on plant cells as they spread.
Fungi reproduce by spores, and can spread rapidly. They prefer damp warm conditions for growth and reproduction.

Fungi are spread by:

  • wind

  • water

  • infected soil.

Disease symptoms are:

  • spots

  • rot

  • mildew and mould

  • a furry appearance when they are mature and producing spores (this is one way of telling the difference between fungal and bacterial infections).

Fungal diseases can be prevented by:

  • maintaining good hygiene (disposing of infected plant material, cleaning tools)

  • making sure the plants in greenhouses have good ventilation and avoiding the wetting of plant leaves

  • using chemicals called fungicides that cover plant surfaces

  • using resistant plants.

Buxus Blight

What is Buxus Blight?

Buxus blight is a fungal disease caused by Cylindrocladium buxicola, affecting the Buxus species (Box). This disease doesn’t kill the roots, but it will weaken the plant. However, if you catch it early, recovery might be possible. 


This disease causes leaves to brown and fall off. In addition, it can infect young stems and cause black streaks. 


If the plant is infected:

  • Prune out the infected limbs

  • Sterilise your equipment between plants

  • Remove all leaves under the plants

  • Spray foliage with a fungicide called Buxus Blight Fighter


  • Check your plants for any signs of the fungal disease

  • Prune once a year as it will reduce the risk of spreading 

  • Ensure a good airflow around your plants

  • Water at the base of the plant 

  • Improve your soil’s health by adding mulch around the trees

Griselinia Root Rot Caused By Phytophthora

What is Phytophthora? 

Phytophthora is a type of root rot existing in the soil. If left untreated, it can cause the decay of roots in plants. In fact, moist soil is a suitable habitat for these fungi. So, it’s vital to have good drainage for the plant. When there is too much water near the roots, Phytophthora spores will travel and can reach the plant’s roots. 

It’s essential to add that phytophthora affects many other plants, not just Griselinia. 


The plant may become yellow or brown when infected with root rot. They can even fall off. These symptoms can worsen if left untreated. In addition, the plant could die because it won’t be drinking water properly. 


If you notice the symptoms listed above, we recommend testing the soil. If it comes back positive with the disease, you may want to consider treating the plant as soon as possible. 

  • Remove affected plants 

  • Replace the soil with fresh topsoil to prevent further spread 


We have seen more and more Griselinia diseases this year because it has been extremely dry. The plant roots get easily damaged because it doesn’t have enough energy to absorb from the dry soil. The Phytophthora will then attack the specie. 

Since this disease spreads fast, we recommend not planting this hedging shrub and looking for alternative species not susceptible to root rot, such as Buxus, Taxus, Ribes, etc.   

However, if you already have Griselinia hedges around your property, we recommend doing these steps to prevent the spread or formation of the root rot:

  • Increase drainage of the soil 

  • Improve the general soil’s health

  • Add mulch


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