Weed of the month for May 2014 is Ground Ivy

Ground Ivy  

Biology: Ground ivy (Glechoma hederacea), also known as creeping Charlie, is a very difficult to control perennial broadleaf weed. It can often be seen growing in the shade and invading turfgrass and other mowed areas throughout the United States. Ground ivy thrives in moist, rich soils located in shaded areas, but will grow in full sun as well. These traits combined with the ability to produce aggressive rooting stolons, tolerate low mowing heights, and shade/crowd-out surrounding plants, help to make ground ivy one of the most difficult-to-control turf weeds in lawns.

Identification: Ground ivy is a perennial broadleaf weed that invades turf through aggressive stolons that ‘creep’ below the turfgrass canopy. It forms very dense, mat-like patches that effectively crowd-out the surrounding turf. Like other members of the mint family, ground ivy has distinctive square stems with two leaves branching from each origin point (node) and emits a disagreeable odor when crushed, damaged, or mown. Leaves are round to kidney-shaped with prominent veins and broad rounded edges. These leaves are held above the canopy by long petioles (leaf stems) which can effectively shade and weaken the surrounding turf. Spreading stolons root aggressively at the node, further making ground ivy difficult to control. It produces flowers from April to June that are tubular in shape, purplish blue with red speckles, lobed petals, and are arranged in groups of three to seven. Ground ivy can often be mistaken for other broadleaf weeds such as common mallow or henbit. However, common mallow has rounded stems and sharply toothed leaf edges while henbit stems do not ‘creep’ along the ground nor root at the nodes.  

Kidney-shaped leaves with deeply lobed edges

Two leaves branch from each node

Dense arrangement of ground ivy leaves
Leaves held atop long petioles (stems)

Square stems, characteristic of the mint family

Spreads via aggressive prostrate stolons

Ground ivy regrowth via aggressive stolons
Ground ivy flowers

Cultural control: Because of its aggressive growth and establishment, there are very few cultural practices that have been observed to effectively control ground ivy. Management practices such as improving surface drainage, watering deeply and infrequently, and cultivating (aeration) compacted soils may hinder the development of ground ivy in favor of a more dense, aggressive turf. Nitrogen fertilization will also provide some reduction of ground ivy cover in turf.

Biological control: None known for specific use in ground ivy. Our preliminary research suggests that iron HEDTA (FeHEDTA) may be used to manage ground ivy with multiple applications.

Chemical control: Because of its aggressive nature and the survivability of stolons, there are no preemergence herbicide options for the control of ground ivy in turf although Gallery (isoxaben) can help reduce the ability of stolons from rooting which will slow the spread of this weed. As a result, management must focus on postemergence herbicides. Repeat applications of two- or three-way mixtures of 2,4-D, dicamba, MCPP, of MCPA may offer fair levels of control. Turflon Ester (triclopyr) typically provides better control. Additionally, products that contain triclopyr or fluroxypyr as one of the ingredients in a two- or a three-combination herbicide will work well. In warm-season turf, Manor (metsulfuron) can control ground ivy when applied in combination with a non-ionic surfactant (0.25%). Most of these herbicides require supplemental applications for adequate control.

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
Leslie Beck, Postdoctoral Research Associate
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European Chafer is at the Root of Spring Grub Damage in Northern Indiana

Reports of spring white grub damage are relatively uncommon in most of the Midwest. However, the European chafer is a slightly different beast and seems to be more cold-hardy than other annual white grubs. This characteristic 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 tends to infest areas with no previous history of white grub damage, including low maintenance areas. Folks in Michigan have been dealing with insect for many years now, but it is relatively new to Indiana; with the adults of this species first being detected in Porter, Kosciusko and Allen counties during 2007. We have now linked recent reports of spring white grub damage in LaGrange and Noble counties to this insect meaning that populations are well established in these areas and are likely established throughout the northern third of the state. Spring grub control is difficult to achieve and the only realistic chemical options are trichlorfon or carbaryl. Even then, repeated application may be necessary. If you notice white 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 (shown above). Once established these insects may require some special attention going forward as they tend to be more damaging and somewhat less susceptible 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 so you can identify areas to watch down the road.

Doug Richmond, Turf Entomologist
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Weed Management is a Prerequisite for Using Neonicotinoid Insecticides

Honey bees and other pollinators forage for nectar and pollen on a wide range of flowering plants, including some of our most common turfgrass weeds such as dandelion, white clover, ground ivy, speedwell, chickweed and a host of others.

If any of these flowering weeds are present at noticeable levels, it may be wise to avoid treating the area with a neonicotinoid (or any other insecticide). In the case of neonicotinoids (imidacloprid, clothianidin, thiamethoxam, dinotefuran), mowing off the flowers before application may not be enough since these insecticides are systemic and may be taken up by the plant and translocated to the flowers when another flush of growth occurs. Lawns that are relatively weed free should not pose a substantial risk to pollinators should a neonicotinoid be applied. Effective weed control should be a prerequisite for using neonicotinoid insecticides. We simply don’t know how much of the material ends up in the pollen and nectar of our most common weeds, but if there are no flowering weeds to take up the insecticide, the risk to pollinators will be significantly reduced. Always avoid spraying insecticide of any type directly onto plant blooms.

Doug Richmond, Turf Entomologist
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Early Season Caterpillar Update

Most of Indiana experienced cooler than normal temperatures over the last week, with good amounts of precipitation providing very good growing conditions for cool-­‐season turf. However, green-­‐up of warm-­‐season grasses has been slow, so we have a relatively mixed bag for insect development and damage. The cooler temperatures and ample rainfall should help mask insect feeding damage in cool-­‐season grasses caused by caterpillars such as black cutworm and armyworm while warm season grasses may be slow to outgrow such damage until warmer weather arrives. Warm-­‐season grasses could also be experiencing delayed green-­‐up due to the feeding activity of hunting billbug adults which seem to be out in force. Unlike the bluegrass billbugs that only cause significant damage in the larvae stage, hunting billbug adults may actually damage warm-­‐season turf, especially when green-­‐ up is slowed by cooler temperatures.

Click on the image to zoom in

The black cutworm risk map (above) has been updated to indicate high risk areas where larval development is likely to have reached the point where damage may be visible. Golf Course Superintendents in the entire southern half of the state should be scouting for this insect and paying attention to suspect areas on closely mowed turf.

Superintendents and lawn care professionals alike should keep an eye open for armyworms. They may be small right now, but as they develop, larger larvae can make a lawn disappear practically overnight. The most susceptible turfgrasses tend to be located adjacent to weedy or unmanaged areas, fence rows, the borders of agricultural fields and ditches where tall grasses provide excellent habitat for the adult armyworms to lay eggs. Check my previous tweet for insecticide recommendations appropriate for cutworms… the same chemistries will also be effective against armyworms.

Doug Richmond, Turf Entomologist
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