Forecasting threats

The usual suspects: (clockwise from top)  a fire ant, cutworm and white grub. Photos: Bugwood.orgForecasting insect pests in the landscape is challenging. Sometimes we take into account how cold or warm the winter has been and try to make a prediction. Other times we reflect back on how serious certain pests were in the previous year and try to make an educated guess. Other times, we observe long-term trends with a certain pest and we can make a fairly confident statement about what to expect. In reality, however, predicting insect pests is difficult.

With that in mind, I’d still like to make some “predictions” for what we need to look out for as the 2010 season gets underway. This will be somewhat targeted for transition zone and warm season turfgrass from the mid-Atlantic area and the Southeast. I’ll stick with the major pests: the white grubs, fire ants, mole crickets, cutworms and fall armyworms, but also throw in a few thoughts about some new problems we see surfacing.
 

Fire Ants
Fire ants continue to spread and impact more people each year. Almost without exception I’ll get questions as to whether or not the winter will affect the fire ants. Based upon the rapid spread of fire ants throughout the South and their introduction into new areas, I think the obvious answer is no. Fire ants are tough and resilient, and bounce back year after year. I don’t really foresee any negative impact of this year’s relatively cold winter on fire ant populations during 2010. In other words, be prepared for full-scale warfare this year to keep fire ants suppressed to an acceptable level.

Crickets and Grubs
Soil insects such as mole crickets and white grubs are rarely affected by cold weather, but can be impacted by dry weather. I anticipate plenty of mole crickets and plenty of white grubs to go around in 2010. Rainfall is often the biggest factor in determining the overall abundance of these pests. If it’s really dry during egg laying (spring and early summer) then fewer eggs may survive. Wetter years often favor grubs and mole crickets and egg hatch often occurs a little earlier, as well.

Figure 1. New pest problems such as the sugar cane beetle are typically misdiagnosed. Figure 2. Fall armyworms seem to be more common each year in the Southeast and often start near landscaping or the edge of the property. Figure 3. The maintenance of high quality turf often makes seldom seen nuisance pests, such as these ground-dwelling bees, into a major problem Figure 4. Fire ants continue to spread throughout the South and are even becoming a threat in buildings.Cutworms and Fall Armyworms
Cutworms are hardy insects that survive the coldest of winters and seem to do well even under dry period and wet periods. Cutworms are one of the most reliable pests we experience – it seems like they’re always out there, but fortunately not at serious levels. The fall armyworm on the other hand is a very serious pest of all types of turfgrass and can do a lot of damage to sod, sports turf, home lawns, commercial properties and golf courses. It’s not the least bit tolerant of cold, and even in a mild winter it overwinters only in the extreme South. This means armyworms survive the winter only in southern Florida and right along the Gulf Coast. Well guess what happened in those areas in the weeks right after Christmas? It got cold, really cold and most likely set back the fall armyworms. At the same time, that was in late December and early January, so there will be adequate time for the fall armyworm populations to recover.

Fall armyworm problems in the Southeast and Mid-Atlantic states have a lot to do with the migration into those areas from their overwintering sites. Weather patterns moving up from the Gulf Coast are in the spring and early summer can result in an earlier arrival of the moths of this pest. Once they arrive they are capable of several generations. It appears one of the strains of fall armyworms that overwinters in Florida has a strong preference for hybrid bermuda and perhaps the increase in problems in recent years is that the proportion of fall armyworms of this strain keep increasing. It’s a sneaky pest that catches us by surprise, but be aware that during the summer and early fall it can attack and the infestations almost always start along the edges of the turf. Birds feeding in the turf are often an early indicator and newly sodded and sprigged areas are particularly susceptible.

Climate Change
No, not that climate change. I’m talking about the turf climate, the ecosystem of the turfgrass we manage. For those of you who have been in this business a long time, you know that the means by which we manage turfgrass, the cultivars we use, the expectations for the appearance of the turfgrass have all changed dramatically. In other words, the climate has changed. It only makes sense then that the pest problems we deal with in turf are going to change through time as well. When I first started at North Carolina State University 25 years ago, I inherited all kinds of publications on insects like sod webworms. In the last two years I have not have a single call about sod webworms in North Carolina and probably had about 10 in the last 10 years. Yet, 30 years ago, sod webworms were a significant problem in both cool and warm season turf in North Carolina.

Bugs to Watch
What are the up-and-coming pests now? Well we know that billbugs are becoming more and more common throughout the South. The hunting billbug is one of the more common species and we’re seeing damage on both cool and warm season turf with the biggest increase in warm season grasses such as zoysiagrass, bermudagrass and paspalum.

We’re also seeing a rapid increase in what was previously an agricultural pest called the sugar cane beetle. This small black beetle overwinters as an adult and attacks warm season turf and is especially attracted to bermuda and paspalum.
 
I’m not saying these are the next mole crickets or fire ants that we will have to deal with in the Southeast, but they are becoming more troublesome and as our industry changes, we must anticipate that the pests will change as well. 
 
The author is a professor of entomology at North Carolina State University.