Garden Pests and Diseases
- Jun 15
- 2 min read
Updated: Jun 24
Regular inspection helps identify problems before they become serious. Check your plants every few weeks during the growing season, paying particular attention to new growth, the undersides of leaves, and stems. Below is your guide to common Garden Pests and Diseases in New Zealand gardens and how to treat them.
Aphids
Look for:
Clusters of small green, black, brown, or white insects on new shoots and flower buds.
Curled, distorted, or sticky leaves.
Ants, which are often attracted to the sticky honeydew aphids produce.
Thrips
Look for:
Silvery, streaked, or speckled leaves.
Tiny black spots (thrip droppings) on leaves or flowers.
Distorted new growth or damaged flower buds.
Small, slender insects that move quickly when disturbed.
Scale Insects
Look for:
Small brown, grey, or white bumps attached to stems and leaves.
Sticky residue (honeydew) on foliage.
Yellowing leaves or poor plant growth.
Sooty black mould growing on honeydew deposits.
Powdery Mildew
Look for:
A white or grey powdery coating on leaves, stems, or flower buds.
Distorted or yellowing leaves.
Reduced vigour, particularly during humid conditions or where airflow is poor.
Leaf Spot Diseases
Look for:
Brown, black, yellow, or purple spots on leaves.
Spots that increase in size or merge together.
Premature leaf drop.
Diseased leaves accumulating beneath the plant.
Buxus Pests and Diseases
Look for:
Leaves turning yellow, bronze, or brown.
Bare patches within the plant.
Webbing or small caterpillars feeding on foliage.
Black streaks on stems.
Rapid leaf drop or dieback of branches.
Prevention
Prevention is always the first and best line of attack with pests and diseases.
Stressed out plants are more likely to be attacked. Keep your plants moist and well fed with nutrients in the soil. The best way to do this is with a thick mulch or compost, mulch will hold moisture in the soil as well as provide your soil with nutrients that your plants need.
Natural air flow is important for plant health. Airflow around and through each plant reduces the damp and still conditions that most pests and diseases prefer.
Early Action
If you notice signs of pests or disease:
Remove affected leaves or branches where practical.
Improve airflow by thinning dense growth.
Avoid overhead watering where possible and water in the morning so foliage dries out during the day.
Keep plants healthy with appropriate watering and fertiliser.
Treat pests or diseases using an appropriate product if required.
Products
Groventive Garden is a good chemical option, it is widely available. It works on aphids, thrips, and scale insectsand is suitable for many ornamental plants. Pair this spray with an oil spray to improve efficacy. Repeat every 14 days until the pests have gone.
Copper based fungicide for powdery mildew and leaf spot diseases. Reapply every 1-2 weeks while conditions remain damp.
Apply buxus specific fertiliser like Topbuxus to the soil around your buxus in mid-October, then every 8 weeks until the middle of Autumn. This controls the risk of your buxus getting the buxus blight disease.
For more advice like this book a Garden Clarity Session with Artful Gardens today.
