Hi,

I sounds like slugs has been having an evening sunflower banquet in your garden. Slugs rasp the leaves with their rough mouth parts taking the tender leaf tissue and often leaving the tougher veins intact. They will in all likelihood consume the flowers and seeds as well if left unchecked. Telltale signs of slug infestation are the slime trails they leave behind on intact leaf tissue.These are likely to be more visible in the early morning. During the day slugs hide under leaf litter, mulch and rocks. Look under the ground cover around your sunflowers and I think you will discover the culprits, possibly in significant numbers. Old mulch makes and excellent refuge for slugs. They thrive in moist, humid environments so, if you can use drip irrigation to reduce the humidity around you plants. If you water overhead do it early in the day so that leaves can dry before nightfall.

The best way to control and then prevent heavy slug infestations is to rake up and dispose of old mulch in the spring and then apply fresh mulch in the summer. I suggest that you do this now for this year. There will probably be a considerable egg bank in the soil so you will have to use other controls as well. You can bury a cup nearly to the rim near your plants, fill it with beer and collect the slugs each morning.  You can also purchase chemical molluscicides that cause slugs to dehydrate and die. They are sold in granular, paste and gel forms at garden centers.

Thank you for sending us your question. It is not too late to begin controlling the slug population in your garden and you now also can make a slug management plan for next year.