I sure don’t want to sound all doom and gloom, but we do need to make sure all our organic pasture and hay growers are aware of a severe problem that is only getting worse. Organic bermudagrass hay or grazing producers should know this insect and unfortunately bermudagrass stem maggot (BSM) is here, and it doesn’t seem to be going away!
If you are not sure about this insect or the damage it causes, then later this spring walk out in your pastures and look at all the dead tips (picture above). This insect has four life stages: the adult is a small fly, the adult lays an egg on the bermudagrass stem, the egg hatches a maggot or small larvae that burrows into the stem and feeds for several days. The feeding it does cuts through the topmost leaves so that they die. These leaves that died look just like a killing frost came through without the cold weather.
Alicia, Coastal and Tifton 44 are the most susceptible since they are finer textured bermudagrasses. Tifton 85, which is a coarser grass, just doesn’t have as much of a problem with BSM as others.
What can you do as an organic producer? One option for mitigating the damage caused by BSM is through harvest management. If damage is found within 1 week of the normal harvest stage, then harvest the crop as soon as weather conditions allow. Once you see the damage, you are not likely to get much more yield. If damage is within 1 to 3 weeks after the previous harvest, it is also likely that the crop will not add a significant amount of yield. The damaged crop should be cut and (if the yields are enough to bale!) baled and removed from the field as soon as weather conditions allow. Leaving the damaged crop in the field will only compete with any attempts by the plant to regrow and decrease the opportunity that the next cutting will have to accumulate mass.
Can you treat organically? Yes, if you need to treat, then an organic pyrethrin or pyrethrin mix is an option. Current recommendations are to treat after a cutting if damage levels are high. Best results have come from treating twice—once a few days after baling the previous crop as the grass begins to resprout and again 5 to 7 days later. Another possibility is the many and varied botanical products (cinnamon, garlic, clove, etc.), but this may be hit or miss! As always check with your certifier before making any treatments. In this dry year we can’t afford to lose any hay to BSM!