Pasture Mealybug Scouting, Management, and Recovery

1.      Scouting

a.      Check edges of damaged areas more than in the middle of dead grass.

b.      Look for leaf damage symptoms such as yellowing and red leaves.

c.      Look for mealybugs on the underside of leaves, especially the lower leaves.

d.      Check the soil surface and thatch below grass canopy for mealybugs. Often a majority of the mealybugs may be in the thatch and on and in the soil.

e.      Mealybugs can be as large as 5 mm in length or as small as 0.2 mm. If larger mealybugs are being found, there may be many more small mealybugs that are difficult to see.

f.        We have not determined a producer/consultant method for determining the size of the populations while in the field. However, if mealybugs are easily found, they are likely above an economic level.

2.      Management

a.      When grass injury symptoms are detected and pasture mealybugs detected, management with cultural and chemical methods may be used to help reduce mealybug numbers.

b.      Cultural control methods include cutting/shredding and heavy grazing. Pasture mealybugs thrive in tall dense forage, eliminating this will reduce the mealybug population.

c.      Chemical control is still being evaluated but there are several insecticides that research has shown have activity towards pasture mealybug.

                                                              i.      Labeled for use in pastures in Texas

1.      Sefina at 8 to 10 fl-oz/ac offers suppression of the pasture mealybug. Research suggests that it should not be used to manage high populations of pasture mealybug or in a crop rescue situation. Its best fit is when crop injury is slight and the mealybug population is not severe.

                                                            ii.      Not labeled but research show are active towards pasture mealybug.

1.      Centric at 2.5 oz/ac has been shown to be consistently effective in reducing mealybug populations. We are pursuing a Section 18 Emergency Use Label for Centric.

2.      Other non-labeled insecticides that have shown good activity in research trials include Imidacloprid at 6 fl-oz /ac, and Sivanto Prime at 8 to 14 fl-oz/ac

3.      Optimizing control

a.      The key reason pasture mealybug is often difficult to control with insecticides is poor insecticide coverage due to tall, thick grass canopies. These steps will optimize control:

                                                              i.      Reduce the biomass. Where damage and mealybugs are detected the best thing to do is to eliminate the canopy by cutting or shredding. Where possible bale the grass to remove as much dry grass material from the field.

                                                            ii.      Allow regrowth. Allow the grass to regrow to 6 to 8 inches in height. The insecticides that show good activity towards pasture mealybug must have green leaf tissue to work.

                                                          iii.      Treat. After sufficient regrowth has occurred, mealybugs are detectable, apply insecticide. Because the canopy is reduced insecticide coverage and activity should be much better.

4.      Recovery

a.      When pastures are heavily damaged a decision must be made to attempt to recover the existing grass or to replace the grass.

b.      Seeded grasses.

                                                              i.      Grass species such as Bahia and bluestems are good seed producing grasses. Depending on the severity and timing of mealybug infestation, these grasses might have produced enough seed to reseed themselves and not require grass replacement.

c.      Non-seeding grasses.

                                                              i.      Some grass species do not reproduce well through seeds and these might be more difficult to reestablish in severely affected areas by themselves.

                                                            ii.      Although we do not have data comparing the susceptibility of various grass species and varieties, antidotal observations suggest there are differences. Thus, far all pasture grasses do seem to be susceptible and subject to injury and pasture dieback. However, it appears Coastal Bermudagrass is more tolerant than Tifton 85 Bermudagrass. Similarly, in mixed stands of Gordo and Medio bluestem, the Gordo was least affected.  

d.      If the decision is made to start over, removing all grass from the field will be better for reducing mealybug survival and should be done as soon as possible. Early September (or before) would be better than October. This will also help in the establishment of the next crop. 

e.      Applying a pyrethroid insecticide to the fallow field may help reduce mealybug numbers, but this has not been studied. The residual control may be enhanced by disking the field immediately after application.

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A word of warning, be cautious about what you read as you on the AI programs as they are not always accurate. AI bots can be used to gather information about almost any topic including pasture mealybugs. 

I read today of one AI bot stating that grass damaged by pasture mealybugs should not be grazed by cattle due to the toxic saliva the mealybug injects into the plant. This is not accurate. Grazing damaged pastures can help manage the mealybug. The pasture mealybug’s saliva is toxic to the plant and I have found no information of it also being toxic to livestock.