European Chafer Causing Serious Damage in Northeastern Indiana

European Chafer Causing Serious Damage in Northeastern Indiana

Although reports of spring white grub damage have been relatively uncommon in Indiana in recent years, there have been a growing number of cases in the northeastern part of the state.
The European chafer Rhizotrogus majalis Razoumowsky is apparently at the root of several reports of large scale and severe damage to turfgrass this spring. This insect is a slightly different beast than our more familiar white grub species. It is significantly more cold-hardy which allows it to feed later into the fall and start feeding earlier in the spring compared to Japanese beetle and masked chafer grubs. It also shows up in areas with no previous history of white grub damage, including low maintenance areas.

Folks in Michigan have been dealing with this insect for many years now, but it is relatively new to Indiana; adults of this species were first detected in Porter, Kosciusko and Allen counties during 2007. With the help of several diligent individuals in the green industry, we have now linked several reports of serious spring white grub damage in LaGrange, Noble and Elkhart counties to this insect meaning that populations are now established in these areas and are likely established throughout the northern third of the state (see Figure 1 and 2).

Figure 1. Home Lawn in Nobel County showing extensive damage from European chafer grubs.

Figure 2. Low maintenance turf area showing patchy damage from European chafer.

Spring grub control can be difficult to achieve and the only realistic chemical options are trichlorfon or carbaryl. Even then, repeated application may be necessary and damage is not likely to be reversed at this late time. A more proactive approach aimed at preventing infestation this summer is more likely to provide a reasonable solution. Recommended products and application timings for white grub control can be found here: http://extension.entm.purdue.edu/publications/E-259.pdf. European chafers may also cause damage to a variety of field, forage and grain crops (see Figure 3).

Figure 3. Extensive, but patchy damage to winter wheat caused by European chafer grubs.

If you notice grub damage this time of year, take a closer look and try to find the larvae in the soil. European chafer larvae can easily be identified using a 10X hand lens to inspect the raster pattern (Figure 4). Once established these insects may require some special attention going forward as they tend to be more damaging and somewhat less vulnerable to traditional insecticide treatments. The best control is achieved using a preventive approach with applications of imidacloprid, thiamethoxam, clothianidin or chlorantraniliprole applied June through mid-July. Keep records of any European chafer infestation in order to identify areas to keep an eye on going forward.

Figure 4. Location (A) and form (B) of the raster pattern in European chafer grubs.

Doug Richmond, Turfgrass Entomologist and Extension Specialist
Email: drichmond@purdue.edu

Follow me on Twitter @doctorDRich

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Hunting Billbug Larvae Overwintering in Indiana

Hunting Billbug Larvae Overwintering in Indiana

We recently discovered that the hunting billbug is capable of successfully overwintering in the larval stage as far north as West Lafayette Indiana. This insect is mainly a pest of warm-season turfgrasses such as Bermudagrass and zoysiagrass and has become a perennial problem in parts of the state where these grasses are cultured. Although we’ve known for several years that this insect overwinters as an adult and produces two generations per year in this part of the country, its ability to overwinter here in the larval stage was previously unknown. Overwintered adults have been the primary management target, but insecticide applications targeting adults may have little impact on the soil-dwelling larvae. Instead of just 2 generations to think about, managers should be aware that 2 separate cohorts may occur.

Figure 1. Hunting billbug larvae found in soil during March 2015.

Figure 2. Hunting billbug adult (actual size = approximately 1 cm).

Figure 3. High- (top) and low- (bottom) cut zoysiagrass damaged by hunting billbug.

This means is that both larvae and adults may be active and present over much of the growing season. This fact could complicate insecticide timing, narrow the spectrum of useful management options and spread damage over a larger portion of the growing season. The following table contains chemical management recommendations based on my experience and those of our colleagues in North Carolina who have been dealing with this exact issue for some time.

Table 1. Chemical management options for hunting billbug based on target stage of the insect.

Target Stage(s)	Active Ingredients	Timing
Adults	bifenthrin, deltamethrin, lambda-cyhalothrin, zeta-cypermethrin	As soon as adults become active (late April – early May)
Larvae	clothianidin, thiamethoxam, imidacloprid, chlorantraniliprole	When larvae are inside stems or crowns or present in soil
Adults & Larvae	clothianidin + bifenthrin (Aloft), imidacloprid + bifenthrin (Allectus) bifenthrin + zeta cypermethrin + imidacloprid (Triple Crown)	When adults and larvae are present or after adults have been active for several weeks

Always follow label directions and recommended application rates


by Doug Richmond and Alexandra Duffy, Department of Entomology, Purdue University

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Weed of the month for April 2015 is Smooth Crabgrass

Weed of the month for April 2015 is Smooth Crabgrass

Smooth Crabgrass  

Biology: Smooth crabgrass (Digitaria ischaemum), is a summer annual grassy weed that is found throughout the Midwestern United states. Closely related to large crabgrass (Digitaria sanguinalis) and southern crabgrass (Digitaria ciliaris), these three species are often considered to be the most problematic weeds in lawns due to their ability to survive extremely low mowing heights, poor quality soils, and dry/hot climates.

Identification: Smooth crabgrass is a summer annual grassy weed that is commonly found in home lawns throughout the US. Smooth crabgrass can tolerate very dry, poor quality soils and is found in multiple cropping systems ranging from agronomics, to landscape, to horticulture, to vegetable gardens, along with both cool and warm season lawns in Indiana. Crabgrass plants are very opportunistic, so look for it to germinate in areas of bare soil like walkways, gardens, newly seeded turf areas, as well as a very open, thin turfgrass canopy.

Germination typically occurs from mid- to late-spring (late March-early May) in Indiana. If germination occurs while the temperatures are still slightly cooler, the plant will remain small for an extended amount of time. As the temperatures warm, more leaves will start to develop and the plant will begin tillering by early- to mid-summer (June). The young leaves of smooth crabgrass will have very little hairs, while large and southern crabgrasses have a dense covering of very fine hairs. All three crabgrass varieties will have a membranous ligule that has a torn or ‘shredded’ appearance.

Smooth crabgrass leaf emerging from coleoptile.

1-leaf size smooth crabgrass.

2-leaf size smooth crabgrass.

3-leaf size smooth crabgrass.

Usually some hairs are present on smooth crabgrass but many fewer than on large crabgrass.

Photo shows membranous ligule and few hairs on leaf sheath or leaf blade.

The development of multiple tillers can contribute to the clumpy appearance of a crabgrass plant, though smooth crabgrass is generally smaller in size than large crabgrass. Once mature, smooth crabgrass produces seedheads in the form of 3-5 spikes that are clustered at the top of long, erect stems. Seedheads mature at the end of summer prior to fall/autumn. As crabgrass dies with the first killing frost, the plant can appear as unsightly brown patches surrounded by green cool-season turf in lawns.

Prostrate growth of smooth crabgrass in short cut turfgrass.

Dense turf keeps out crabgrass. Here a patch of creeping bentgrass in a lawn is keeping out the crabgrass.

Chilling injury to crabgrass in cool fall months prior to the first frost.

Brown, dead crabgrass plants in a lawn following the first hard frost.

Cultural control: Maintaining a high quality lawn through higher mowing heights, proper fertilization (some fertilization is always better than none), and supplemental irrigation during drought will help the desired turf to outcompete crabgrass.

Biological control: None known specifically for control of smooth crabgrass in home lawns.

Chemical control: For more information about crabgrass control, see our recent post, Common Questions About Crabgrass Germination and Preemergence Herbicides Answered.

Both smooth and large crabgrass can be controlled using preemergence and postemergence herbicides.

There are multiple options for preemergence herbicides that are available for purchase by homeowners, including dithiopyr (Dimension), pendimethalin (Pendulum), and prodiamine (Barricade). These herbicides prevent the crabgrass from successfully germinating. For adequate control, these products must be applied before the crabgrass starts to germinate. One exception is dithiopyr, which has the ability to control crabgrass after it germinates until it reaches 1- to 2-tillers in size.

Once the crabgrass has already emerged, another option for control is the use of postemergence herbicides. Products that include active ingredients like dithiopyr (smaller than 1- to 2-tiller in size), quinclorac (Drive), mesotrione (Tenacity), fenoxaprop (Acclaim Extra) can be used to adequately control crabgrass that has already emerged. Each of these individual fertilizers provide a slightly different spectrum of control and works well on specific sizes (based on number of tillers) of crabgrass. Homeowners can choose a product based on the size of their crabgrass as well as its ability to control other weeds that you might have present.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist, Purdue University

Leslie Beck, Weed Extension Specialist, New Mexico State University

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