Tuttle Mealybug Update
Tuttle mealybugs, a pest of zoysia grass, are surprisingly difficult to control. According to UF/IFAS Extension Entomologist Dr. Adam Dale, there has been a significant increase in Tuttle mealybug outbreaks/reports throughout the state since 2016. It’s not clear if this is because more people are planting zoysia, have had it in their yards for a while, or if the insect itself is dispersing and causing more problems.
It is important to consider the cultural practices being used to maintain the lawn(s). Nearly everything originates with cultural practices. Also, Tuttle mealybug seems to have some seasonality. So, as infestations go into dormancy for the winter, it’s not worth directly managing the insect. Most frequently , outbreaks occur towards late summer and into the fall, so getting ahead of them by managing them in the spring is important.
One of the biggest factors that seems to facilitate Tuttle outbreaks is thatch buildup. Zoysia lawns that have accumulated a dense thatch layer typically have higher mealybug infestations and those infestations are much more difficult to get under control. These insects are very well equipped to hide in the thatch, avoiding direct contact with insecticides and other predators or adverse environment conditions. The thatch can also prevent insecticides from getting down to the lower plant tissue and roots, where some of the systemic products need to be taken up and spread throughout the plant. Thatch management is key to zoysia management AND Tuttle management.
Another major issue is that our most commonly used and affordable systemic products are neonicotinoids (Class 4A). Although there is no confirmed evidence of resistance anywhere in the state, repeat applications of the same chemical class is setting the stage for insecticide resistance and the loss of a control tool. Dr. Dale recommends using other chemical classes, like Mainspring (Cyantraniliprole, Class 28) or even azadirachtin (class 18B). Though insecticides are limited in options, everything possible should be done to avoid resistance.
The keys to more effective control appear to be:
- Thatch management. Verticutting (removing thatch) in the spring.
- If there is a known infestation, immediately (within 2 weeks) after verticutting, make an insecticide application.
- Use a systemic insecticide that the mealybugs will ingest as they feed on the plant sap. Do not rely on contact-toxic products.
- Rotate chemical classes between insecticide applications (more info here). This is very important because mealybugs are highly likely to develop resistance to insecticides.