I have a couple of sunflowers in big pots on my balcony for about two months now and suddenly holes started showing up on the leaves. It's not just the edges - they have holes right in the middle of the leaf like something's eating through them. What could it be?
The holes in the middle of the leaf are almost definitely spider mites or thrips, but here's something most people miss: if your sunflowers are on a balcony and it's hot and dry, those bugs multiply like crazy. When I had sunflowers in pots a while back, the same thing happened to me and what worked was spraying the leaves (especially the underside, where they hide) every two days with water and a few drops of neutral soap, without overdoing it. Do you notice if the leaves have yellow spots or like really fine webbing? That would confirm spider mites. Either way, the first thing is to check the underside of the leaves with a magnifying glass or up close to see if there are bugs moving around there; if you see little things, then you know exactly what you're dealing with.
I've had that same problem with potted plants, and it's usually been spider mites or thrips - they leave those characteristic holes in the middle of the leaf while they're eating through the tissue. Look carefully at the underside of the leaves with a magnifying glass or your phone to see if there are tiny dots or little bugs, because if it's that you'll need a miticide or a specific insecticide, but if you only see the holes without spotting anything, it could also be a less common pest like small beetles that feed at night.
Before you blame spider mites or thrips, first check if there are red spider mites or white powder on the underside of the leaves, because those bugs leave unmistakable signs. What you're describing sounds more like borers like beetles or whitefly larvae, which make that clean hole pattern in the middle. A quick way to tell is to run your hand under the leaf and see if dust comes off or if you notice movement.
The thing is, on balconies with air circulation and no humidity control, these little bugs feel right at home. If the place is warm and dry, the population definitely explodes, but that also happens if there's poor ventilation or if you water without letting it dry between waterings. Check if there's weeds nearby or leftover dead plant material that could be a pest hotspot. Gently shake the pots over a white sheet: if you see bugs falling, you've got your culprit confirmed.
For treatment, a homemade spray of water with neutral soap works pretty well if you catch it early, and you need to repeat every 3-4 days. If it's heavily infested, you might need a specific insecticide, but first try to improve air circulation on the balcony and cut back a bit on watering frequency. Once you get the pest under control, make sure to keep the leaves clean, because often insects take advantage when there's dirt or dust buildup.
Holes in the middle of the leaf (not on the edges) are almost always from spider mites or thrips, people already mentioned that here 👍. But what's missing is that these pests hate humidity, and that's your secret weapon: spray the leaves every two days with clean water, especially the undersides where they hide. If your balcony is dry and warm, they're having a party there.
Another practical thing you can try before using chemicals is wiping the leaves with a soft damp cloth (go easy so you don't tear them) and if you see the damage is bad, make yourself a homemade spray: water with a few drops of neutral soap or mild detergent. Spray everything well, including stems, every 3-4 days. Sunflowers can handle it pretty well so don't be scared to be generous with water on the leaves.
If it doesn't improve in a week or two, then consider getting an acaricide or insecticide specific for thrips/spider mites (they sell them at any garden center). The important thing is to be consistent, because these bugs won't go away on their own 🌻
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