Unfortunately, it’s the time of year that I begin getting calls about defoliated hay fields, sod, and other crops. While not always the culprit, armyworms have been an issue for at least two of our producers this season. If you are not scouting and looking for these damaging pests, this is your call to begin doing so!
The fall armyworm (spodoptera frugiperda) is native to southern tropical climates and is present in almost all states east of the Rocky Mountains. It is most prevalent in the Southeastern U.S. including Georgia. Recently, armyworms were reported for the first time in Africa, so it is now becoming a pest of global proportions.
The armyworm life cycle begins when females lay up to several hundred eggs that hatch in 2-3 days. Once hatched, larvae go through six instars, or periods of development. At early stages, the larvae are small, less than a tenth of an inch in length and aren’t as destructive as their more mature counterparts. The older larvae grow to approximately an inch and a half in length and are easy to identify with their brown body, white stripes, dark spots, and white inverted “Y” on their head. The larval stage lasts around 14 days during the summer and 30 during cool weather. The armyworm then undergoes a pupal phase before turning into a small grey moth. Fortunately for us, this species does not tolerate cold weather and does not overwinter in Georgia, but they are good fliers and do migrate into our region each year nevertheless.
Fall armyworms can cause significant damage to over 80 different crops the most susceptible of which are turfgrasses and forage crops like bermudagrass, bahiagrass, and other grass mixes. Damage from armyworms comes from their larval forms, which will destroy foliage of these species. Young larvae will eat leaf tissue from one side, leaving the epidermis of the leaf intact, but older larvae quickly begin eating through the centers and edges of the leaves. A population of end stage armyworm larvae can defoliate an entire pasture or hayfield in less than a week.
It is essential that producers have an appropriate scouting program so that armyworms are identified when they are less than half an inch in size. At this early stage of development, the armyworms are not causing severe damage and are much easier to control with insecticides. The larvae do not like bright light or heat, so it is best to scout early in the morning. Examining the entire turf or forage crop is essential, and be on the lookout for other indicator species like high bird and wasp populations. Scouting should continue through the end of September and early October. The threshold for treatment of armyworms is the presence of 3 or more caterpillars per sq ft of forage or turf. If you need further assistance with armyworms or insecticide recommendations, contact us at uge3181@uga.edu or 706-359-3233.
