The Department of Primary Industries and Regional Development, nurseries and rose growers have been inundated with photos and specimens of roses that are suffering from all sorts of symptoms which include:
- Silvering of the leaf surface.
- Curled and distorted leaves with bronzing on leaves, stems and new shoots.
- Grey to black markings on flowers often showing a ring of scarred tissue around the apex.
- Flower buds reduced in size, have a brown colouring and fall off before development.
- Flowers are paler in colour with a brown tips.
The culprit causing the damage are Chilli Thrips known as Scirtothrips dorsalis, a tiny insect less than 2mm in length. These thrips have a punch and suck action, they puncture a hole in plant cells and suck up the sap, this is what causes the mottled effect on the leaves and brown scarring on the rose buds.
Chilli thrips are most active in spring, summer and early autumn if it’s warm and dry. This is their preferred weather and ideal for breeding. Thrips are hard to see with the naked eye but if you get a plain sheet of paper and tap the leaves or flower you may see them moving on the paper. The life cycle of Chilli thrips is complete within 15 days and includes egg, 2 instar larval stages, prepupa, pupa and adult. Eggs will hatch between 2-7 days.
These pesky little insects are polyphagous; meaning they will feed on many different plants. They are now a widespread pest found in Pakistan, Japan, the Solomon Islands, Australia, South Africa, Israel, the Caribbean and America.
Before you reach for the systemic insecticide its worth knowing that they have many predators like lacewings, ladybirds, predatory thrips and predatory mites.
In preparation for Chilli Thrips
As the weather warms up it is inevitable that chilli thrips (Scirtothrips dorsalis) will return to our gardens attacking roses, strawberries, chillies, citrus and many other veggies. The best tactic is to take preventative action early rather than waiting for numbers to build up to plague proportions.
Chilli thrips are hard to see without a magnifying glass, but their tell-tale symptoms are easily noticeable. You will see brown scarring along the leaf veins, flower buds drying turning brown and not forming, light brown spots on stems, curled and dried leaves, and deformed new shoots or flower buds.
Thrips start as an egg, then a larva, pre-pupae and finally a winged adult. After feeding on new shoots the larvae fall to the ground until they reach adult stage and develop wings. They can have many generations and numbers build up quickly particularly in warm weather.
If you have thrips, always collect fallen leaves as this helps prevent the larvae from developing into winged adults and laying eggs.
Spray plants thoroughly with insecticides (listed below) when symptoms first appear, particularly spring flower buds. If you had a really bad infestation last year you may need multiple fortnightly sprays of different products.
If preventative spraying has been left too late, hard pruning of badly affected stems is recommended, bag all pruning’s, and pick up fallen leaves so the life cycle doesn’t continue. So many rose growers resorted to removing their roses last year, but if preventative action is taken when they emerge in spring hopefully the problem won’t be as bad. Management will take commitment and perseverance with severe infestations needing treatment every 7-10 days. All infested growth should be pruned off and pruning tools cleaned between roses. Do not put cuttings in compost or leave it on the ground, bag them before binning them. There are several organic and chemical options for gardeners but will require repeated applications.
Always check for beneficial insects and pollinators before spraying anything on your plants, organic, botanical, or systemic. Be aware that some systemic insecticides containing imidacloprid is harmful to bees and other insects that feed on the sap of plants or collecting pollen. Botanical Insecticides registered for Thrips control that contain pyrethrums, Potassium soaps, Fatty Acids and ethanol, Spinetorum, Botanical Oils.
Organic gardeners can spray with OCP Eco-Oil, Natrasoap Insecticidal Soap, Beat-a-Bug Natural pyrethrum, Yates Natures Way Vegie and Herb spray, Searles Ecofend Natural Solutions mite and insect spray, Hortico Insect Killer Tomatoes and Vegetables, Sharp Shooter Natural Pyrethrum.
If gardeners need to go for stronger more systemic sprays remember some may have a detrimental effect on bees and other beneficial insects. Products that contain active ingredients such as imidacloprid, acetamiprid, spinetoram, or pyrethroids are effective against thrips, and may be available to home gardeners.
Conguard, Success, Mavrick and Richgro Bug Killa have been used by rose growers with some successes are all systemic insecticides that are registered for the control of chilli thrips.
Top Tip: Place blue coloured sticky strips in rose bushes to discover what sap sucking insects are in your garden – use a magnifying glass to get a better view.
Thrips & sucking insects – botanical based registered products
Top Tip
Don’t use any oil-based sprays when temperatures are above 32 degrees as the leaf tissue on plants may burn.
https://www.agric.wa.gov.au/horticulture/chilli-thrips-roses#:~:text=Chilli%20thrips%20(Scirtothrips%20dorsalis)%20are,leaves%2C%20stems%2C%20and%20shoots.
Perfect lawn is the number-one goal for many home gardeners.
Lawn is not necessary in all landscapes but it has an important cooling effect around a house and provides a place for kids, pets and adults to play. If shady trees are planted in or on the boundary of lawns the cooling effect is even greater.
We don’t need vast amounts of lawn around our houses but we certainly need some to offset the urban heat island effect that hard surfaces and lack of public open spaces are creating. Green spaces entice us outdoors to live a healthier and less stressful lifestyle.
The most important factor in growing a good lawn is preparation. If you do the right prep and select the lawn type suitable to your conditions it shouldn’t use any more water then your garden beds. I know lawn has a water-guzzling reputation but it’s just not true.
Soil: You will need to get the soil right. If you live in sandy soil you will need to incorporate clay, loam, compost, wetting agent and slow-release fertiliser like Grow Safe. If you live up in the Hills you will need to build the soil profile but don’t use any clay.
Wetting agent: its imperative you use a wetting agent and retainer use Soak Up its important for your lawn’s health.
Mowing: If your lawn is subject to heavy water restrictions and may experience drought-like conditions, then the lawn mowing height should be increased. This will allow the lawn leaf and thatch layer to insulate the soil against heavy water loss from evaporation and the end result will be greater lawn health — using less water, as summer progresses.
Regular mowing is needed in summer — healthy lawns will benefit from fewer weeds and more green leaf with less invasion of the grass into surrounding garden beds.
Liquid fertilising: Using the Lawn Love every month delivers nutrients directly to the leaf blades and is absorbed immediately. Lawn Love will help your lawn become less suitable to disease attack.
Granular Fertilising: Lawn is probably the most over-fertilised plant in your garden. People throw it around like chook food. If your lawn is established, it doesn’t need phosphorus. If you have done the preparation when laying the lawn, it should only need to be fertilised at the beginning of spring, summer and autumn. Use Grow Safe fertiliser, you only need one handful per square metre. If you use more it goes straight into our waterways. The other important thing to note is the more you fertilise, the more you have to mow.
Beware the thatch: Watering a heavily thatched lawn will waste a lot of water. The water just sits on top of the thatch and evaporates before it goes into the soil.
Lawns should be de-thatched (verti-mowed) whenever is necessary and done so in the spring.
Varieties such as buffalo or kikuyu can be mowed much lower at the beginning of spring instead — as an alternative to vertimowing and to reduce thatch.
Seven favourite lawn varieties for WA gardens
1. Sir Walter Buffalo
This is one of my favourite lawns after two big dogs and a family that hammers my back lawn. It’s been trouble-free and looking great for 10 years now.
Sir Walter is a soft-leaf buffalo with deep roots, a low thatch habit and a tight growth sward. It stays greener throughout summer and winter and is disease resistant.
Another benefit is that it has proven shade tolerance so this makes it ideal for small courtyard areas and under trees.
2. Sapphire
Sapphire is a very soft-leaf buffalo that is about 17 per cent finer than other soft-leaf buffalos when it is mature.
It’s one of the more frost-tolerant lawns, coping with -10C. in winter, so is a good one for inland and down south. It is a deep blue-green colour, grows well in dappled shade, is drought tolerant and out-competes weeds.
3. Palmetto
Palmetto is a soft-leaf buffalo variety with great shade tolerance. Like Sir Walter, it is drought-tolerant and maintains its deep green colour throughout the year.
It’s a good lawn for kids and dogs alike and outruns any weed competition.
4. Empire Zoysia
You may know Zoysia by the name of Empire or Empress grass. A fantastic drought-tolerant lawn, it has a soft leaf shaft, making it a great lawn for small children.
The downside of it is that it has a slower growth rate than other lawns and takes a long time to recover if you have a few kids and dogs. The upside is that it requires much less frequent mowing.
5. Envy
A beautiful soft leaf-lawn that is known as Queensland blue (Digitaria didactyla), Envy is a very soft dense grass with a beautiful blue-green colour.
It needs full sun and does well in coastal areas with high humidity but doesn’t thatch up like couch. It is slower growing and less invasive then couch but not as drought-tolerant as the buffalo types.
6. Kenda and Village Green
This is Pennesetum clandestinum, which is a sterile form of kikuyu that does not produce viable seed, eliminating the problems with seed dispersal into native bushland. Both types manage to survive the winter better and produce a dense rhizome growth, making them more drought tolerant.
This is a good turf for dogs and kids.
These lawns will need full sun and are practically indestructible, surviving neglect and extreme heat.
7. Matilda Buffalo
Matilda is a soft buffalo lawn with its own unique strengths and characteristics which separate it from the other soft-leaf.
Matilda is a semi-dwarf buffalo lawn, which simply refers to Matilda having finer and thinner stems and stolons, a trait which is unique among the better-selling and better- quality buffalo lawn types. The leaf width is narrower than common buffalo and Sir Walter, and wider than sapphire, with a leaf width approximate to palmetto.