Managing Pastures After a Big Pasture Mealybug Year

Last summer and fall we learned what Pasture Dieback was the hard way as many pastures and hayfields experienced grass loss caused by the pasture mealybug. What we know at this point is mostly what we can learn from the Australians, who have been studying the insect pest for over 10 years.

The primary solutions they have found in Australia are:

1. Manage for Recovery
2. Improve the Pasture
3. Sow a Break Crop
4. Treat the Pest/Pathogen

Manage for Recovery

The best thing to do in the winter and spring is to manage the pasture for recovery from last year's damage.  This includes fertilizing at proper rates, managing invading weeds, and adjusting stocking rates to forage production. I understand rainfall will have a significant impact on all these management practices.

Fertilization is a key to production of healthy hay and forage. While some research shows high fertility rates can also cause mealybug populations to increase, this may be manageable by grazing or cutting hay early to keep from having excessive forage.

Heavily damaged parts of the pasture will be more susceptible to invading weeds. Thus, it is important to monitor weed growth to make timely herbicide applications.

Much of the research from Australia shows the intensity of grazing can have an impact on the mealybug populations. Manage cattle on pastures to keep stocking rates high enough to prevent excessive grass growth.

At this point, we don't know much about the tolerance level of alternate grass species. We have learned that our more common pasture grasses, bermuda, bahia, and the bluestems, are susceptible to being damaged from the mealybug. The Australians encourage incorporating legumes into affected pastures, but there are pros and cons to doing this.

Managing the pasture mealybug with insecticides is not an option right now. Of the five insecticide tests I conducted, only two had favorable results so I do not have sufficient research to make insecticide recommendations. When insecticides are better researched and labeled for control of pasture mealybug, alerts will go out as soon as possible.

Last week, I scouted around the Victoria area and did not find mealybugs. We know the insect winters in the soil and we will be monitoring fields that had problems last year to determine when they begin to be found on the plants.

This spring and summer we will be conducting research on the following topics: 

1. Insecticide screening
2. Timing of insecticide applications
3. Emergence timing
4. Scouting methods