Beetlemania, not Beatle…you know what I mean!
Scarab beetles make up more than 30,000 species worldwide, which really represents only about 10% of the known species of coleopterans. These figures may be mind-boggling in terms of species diversity, but most turf managers in the continental US only have to be aware of less than a dozen. That number is significantly reduced as you travel from east to west across the nation. Many higher populations occur in the eastern and central portion of the country where damage can be most significant.
Most members of the order coleoptera undergo full metamorphosis, meaning that they will experience 4 life cycles starting with the egg which hatches into a larva, then will enter a pupal stage before emerging as an adult. The larval stage of scarab beetles is known to be a fleshy, whitish six-legged-worm-looking C-shaped grub. While white grubs have been discussed ad nauseum for decades, some of our management approaches have begun to change…again.
Knowing that these insects belong to the same order does not mean that they all act alike. Some will exhibit different feeding patterns, or an appetite for different matter or even dissimilar life patterns. It is for these reasons that we will take a few minutes to talk about some factors that set the most common offenders apart.
Our usual suspects include the Japanese beetle, masked chafers (Northern and Southern), European chafers, Asiatic garden beetle, Oriental beetle, May/June beetle and Green June beetle. There is one more wrongdoer that can present a great deal of turf damage, and that is the black turfgrass ataenius (BTA), but they conduct most of their feeding on close-mowed turf or golf course turfs and are not as pertinent to our discussion of white grubs in the lawn setting.
Considered a non-native or exotic species, the Japanese beetle was introduced in 1916 in New Jersey. Since then, they have progressively dispersed through most states east of the Mississippi River, leaving Florida as the only state not infested. Their path has also led them to several states even further westward.
This species tends to be one of the more problematic ones as they will feed heavily during both the larval stage and the adult stage. Large populations of larvae can inflict massive damage to turf, particularly if it is stressed. Adults will attack over 300 species of ornamental plants, leaving damaged fruits and lacy looking skeletonized leaves in their wake.
These insects add insult to injury because they emit a pheromone while feeding, attracting others and possible mates to the same plant where they congregate, and damage ensues at a greater pace.
Japanese beetles have one generation per year with the adults emerging from below the soil surface mid-summer to leave landscape plants looking mangled for the later portion of the year. They then return to the soil where eggs are laid waiting to start the below-ground feeding process.
Optimum timing for control is when first instar grubs are young or newly hatched and feeding voraciously, which is normally mid to late summer. As these grubs mature and enter later instars, they become tougher and more tolerant to insecticides making management much more difficult.
If that isn’t enough to frustrate many, these same white grubs are a tasty treat to many foraging vertebrates, including skunks, armadillo and others which indiscriminately will dig and pull back damaged turf seeking out a meal, making the lawn look like someone ran a rototiller through it. Adults are day fliers, easy to spot and identify, which will help the call to action.
For the sake of brevity, I will condense this group from three different but similar species. This group includes the Southern and Northern masked chafer along with European chafers. These three are mostly similar in their activity, with some minor differences.
The Northern and Southern species are considered native, whereas the European is exotic or invasive.
All three tend to be night fliers and attracted to light sources. They also will do most, if not all, of their feeding in the grub stage. The major difference between then is that the European chafer can sometimes have a two-year life cycle, but all are considered important turf pests.
This insect, also a non-native, is moving westward at a slow pace. There will normally be one generation per year but there is some potential for two in the southernmost regions. AGB is not often thought of as a major turf pest as it tends to do more of its damage as an adult on ornamental plants, and even that is not severe. It does prefer weedy areas for feeding as a grub and is said to be particularly drawn to orange hawkweed, which is, as its name states, a weed.
Adults are night fliers, so even more reason for them to be less conspicuous. The species’ highest concentration lies in the Northeast.
GJB may represent the largest in physical size of the discussed culprits, reaching up to 1 inch in total length. This makes these goliath-like beetles somewhat ominous, but detection may only take a keen ear at times.
Most beetles are not overly achieved masters of flight but this one is known to bounce off non-moving obstacles with some normalcy.
It is a native beetle that does exhibit some different behaviors. First, as a grub it may emerge from below the soil surface, leaving behind a worm-like pile of soil and even crawl or wriggle on its back looking like a caterpillar. Most other grubs will not leave their below-grade hideout. They also will most likely be morning fliers when searching for meals, and they will dine heavily on fruit to the point where entire small fruits will be consumed.
These patterns make it far less of a standard turf pest.
This is another invasive species found to be much more plentiful in New England.
Larval feeding may not be limited to turf; this one has a broader palate and especially enjoys dining on ornamental plant and vegetable roots.
It does do a larger percentage of damage below ground in its larval state but will also feed on some plants once emerged as an adult. Pay special attention to daisies, petunias, phlox and roses if a population is expected. Typically, we would expect to see one generation per year.
Though a misnomer, these insects may sometimes be referred to as June bugs. What is true is that May/June beetles belong to the genus Phyllophaga and there are over 200 known species in the U.S. to consider.
What is beyond the norm is that this beetle will generally have a two- to three-year life cycle. This becomes a little bit more important when we discuss control measures.
Similar to the green June beetle, it is larger in size and like many others is less than accomplished in flight skills. Again it is common for them to collide with fixed objects during their evening flights.
This species also tends to be more plentiful in the Northeast but will spread throughout the eastern half of the country. Lastly, it is somewhat unusual to find a heavy population.
Many of these insects can do a great deal of damage and control methods often are necessary where population levels reach a particular threshold. The reason for this threshold is that healthy turf can often withstand and outgrow the feeding of just a few white grubs.
The problem arises when numbers reach a certain point. High density for white grubs is thought to be in the range of five to 10 per square foot. You will only be able to determine populations by doing some monitoring.
Areas of heavy feeding will present much like drought stress and can be confusing without taking a closer look. If on closer inspection the turf pulls back like carpet, it’s a good sign that there is some extensive grub feeding damage.
At this point, all is not lost because this usually shows up later in the season when seeding is far more successful, and the tiny white grubs do a good job of loosening the soil for a nice seed bed. Another truth about grub problems is that they tend to wax and wane. For instance, I’ve seen little for both grub activity and adult flight in some of Northeastern Ohio, but you can be sure that we will see another wave in the coming years.
Identification is important in determining what species of grub you are dealing with. All grubs have spines or hairlike structures on the tip of the abdomen called the raster. By using the layout these spines or the rastral pattern, you can positively identify the grub then assess the need for management.
The other aspect that makes identification important is assigning the timing for an application. Luckily, most of the single generation beetles are emerging, laying eggs and hatching fairly close to the same time. The exceptions are BTA and May/June beetle, which are either multi-generational (more than one generation per year) or they have a multi-year life cycle.
There are also some climactic and weather conditions that play a role in beetle activity. Rainfall can sway populations one way or the other. Saturated soils will have low oxygen content, making it difficult to survive if it is over a long period of time. Conversely, extreme drought can impede egg development so we can sometimes get help from mother nature.
With regard to control, until the early 1990s we had very few options. More often old chemistry like Sevin (carbaryl), Oftanol (Isofenphos) and Dylox (Trichlorfon) were used. These materials had very short residual so preventative management was really not effective.
Some are also not available any more. Once Merit (Imidacloprid) and Mach II (Halofenozide) hit the market the game was changed, and the notion of preventative control became a reality. These two chemistries, though pricy at the time, became the industry standard for what was called “season long control” and the use of Merit is still strong today.
In 2002, the EPA cancelled Mach II, leaving imidacloprid to handle the heavy lifting. Since that time, several same-class chemistries including Arena/Aloft (clothianidin) and Meridian (thiamethoxam) have arrived. Clothianidin will also get late season control up to third instar grubs. Merit is also found commonly in granular fertilizer combination products allowing for two functions to happen at one time, fertility and grub control.
The problem arises in that all of these products land in the class of chemistry called neonicotinoids and have come under great scrutiny in recent years. In fact, some have been banned in particular states or counties and that movement is gaining momentum. Meanwhile, some of the old favorites, Dylox and Sevin, are still being used for rescue or curative treatments.
There is, however, a light. The Anthranilic Diamide class of chemistry brings exceptional preventative control with some potential for early curative activity.
These materials include Tetrino (Tetraniliprole), Ference (Cyantraniliprole) and most well known, Acelepryn (Chlorantraniliprole), which has just recently been launched by FMC as Durentis. The beauty of Durentis is that the AI load is higher, resulting in even lower per acre rates.
Both Durentis/Acelepryn and Ference are showing outstanding control when applied earlier in the season with some good activity on early post grub control. This offers more flexibility and ease of watering in with early season rainfall more likely.
Though the industry has sought more biorational methods of control, and some have emerged. Some Bt (Bacillus thuringiensis) products along with Milky spore and parasitic nematodes have been on the market for some time, however control is generally fair at best.
Contact myself or Pat Gross, Ewing’s Tech Team, for more information on grub control and other turf questions. Email me at klewis@ewingos.com or call/text 480-669-8791. Email Pat at pgross@ewingos.com or call/text 714-321-6101. We’re happy to help.