Sunflowers Can Be Critter Magnets

Q. After this last rain and gusty winds some sunflower leaves are scorched. The sunflowers are 3 feet tall, sown from seeds saved from last year. The leaf scorching runs between the veins but not on all the plants.  Is this normal after this kind of weather?

A. This had nothing to do with the weather. Look at the bottom of the leaves. Sunflowers are notorious bug traps. If this scorching is from bug damage, you will find lots of bugs feeding on the bottom side of the leaves.

Bottom leaves of sunflowers beginning to scorch showing signs of pest problems on the underside

Bug damage is noticed on the lowest leaves first and progresses up the plant. Usually insecticidal soap sprays applied to the bottom of the leaves kill these critters but will not repair the damage they created.

If the lower leaves turned yellow, it could be from not enough nitrogen fertilizer. If they are 3 feet tall, they have already removed a lot of nutrients from the soil to get that large. Feed them once a month with fertilizer or they will run out of food, the lower leaves turning yellow and scorching.

Checking on the undersides of the leaves we can see aphids beginning to colonize, perhaps placed there by ants moving them into virgin territory

Another possibility is irrigation or damage from salts. They go hand-in-hand since water washes salt from around the roots and pushes it deeper. Little plants only require small amounts of water. Big plants require more water so make sure they are getting enough water and it is applied often enough.

Improve the soil at the time of planting with compost, feed the plants regularly with a fertilizer, water them enough and check for bugs. Then they will be healthier.