Dear Experts
Which insecticide do I need to use for Assorted DAHLIA and Hydrangea Miss SAORI ?
Photos attached showing issue with leaves
Thx
Hi @zillah ,
Looking at the photos, I’m not seeing anything that clearly points to insect damage. Before recommending an insecticide, can I check whether you’ve actually noticed any insects on the plants? Things like aphids, mites, caterpillars or thrips would normally be visible on the undersides of the leaves.
A good general‑purpose, plant‑safe option is Eco‑Oil, which is widely used for common sap‑sucking pests. If it does turn out to be an insect issue, Eco‑Oil will take care of most of them.
However, the leaf damage you’re seeing could just as easily be caused by environmental stress. Both dahlias and hydrangeas can mark or scorch if they get too much sun, not enough water, or irregular watering. Hydrangea ‘Miss Saori’ in particular prefers morning sun and afternoon shade, and it can brown or crisp quite easily in hot conditions.
A few questions that will help narrow it down:
The soil in the photos also looks like fairly poor, compacted ground. Did you dig out the planting holes and replace the soil with a higher‑quality garden soil? Dahlias especially like rich, well‑drained soil, and hydrangeas perform much better with improved organic matter.
If you can provide a bit more detail, we can work out whether you’re dealing with insects or whether it’s more of a watering or sun‑exposure issue.
Please let me know if you have any questions.
Mitchell
Thx Mitchell
1-I have not noticed any insects on the plants
2-I water plants every few days
3-They are exposed to sun long hours I would say 8 hours
4-My soil is bad normally when I dig hole and using potting mix and I don't relay on my soil as it is very poor
»However, the leaf damage you’re seeing could just as easily be caused by environmental stress«
I have feeling it is that
»and it can brown or crisp quite easily in hot conditions«.
I guess you are right Mitchell
Appreciate your help Mitchell
Thanks for the extra details @zillah. Based on what you’ve shared, this really does sound like environmental stress rather than insects. With 8 hours of sun and only being watered every few days, both your dahlia and your Hydrangea ‘Miss Saori’ are very likely struggling with heat and moisture loss.
Here are a few steps that should help improve things:
• Increase watering frequency: In summer, especially with long hours of sun, watering every few days usually isn’t enough. Aim for at least every two days, and if the temperature goes above 35°C, water daily. Check the soil in the top 10cm. If it’s starting to dry out, it’s time to water. The goal is for the soil to stay consistently moist but not soggy.
• Give them some shade during the hottest part of the day: Hydrangea ‘Miss Saori’ especially dislikes harsh afternoon sun and can scorch very easily. Adding a temporary shade cloth to block the midday and afternoon sun will reduce stress dramatically. Dahlias also appreciate protection during extreme heat.
• Improve soil quality gradually: You mentioned your soil is very poor. Using potting mix in the hole is helpful, but over time the roots reach the surrounding soil. When you have time, consider adding compost around the base to help improve moisture retention.
With more frequent watering and some protection from the hottest sun, you should see the newer leaves coming through healthy again. Feel free to update us with more photos if things change or if you’d like more help.
Thx for your help
