Rutgers Turf Blog

Risks to Soils and Plants from Saltwater Flooding

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As you might expect, we are receiving questions from county agents, landscapers, and property owners about saltwater flooding effects on soils and plants and the appropriate remediation. The information below may be helpful in answering these questions. (Thanks to Stephanie Murphy for pulling together a lot of this information).

Problems from Saltwater

There are a number of potential problems caused by saltwater including: i) the direct effect of burn (osmotic stress) on plant tissue; ii) dehydration of plants (physiological drought stress) caused by increased osmotic potential in soil; iii) plant damaged by sodium (Na) toxicity; iv) loss of soil structure caused by excessive Na; and v) soil infertility caused by increased soil pH (excessive alkalinity). [Read more…] about Risks to Soils and Plants from Saltwater Flooding

Daconil Action Fungicide

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Have received several questions from golf course superintendents over the last few days about potential phytotoxicity from the use of Daconil Action (cholorthalonil + acibenzolar) on golf course greens and fairways.  I have worked with Daconil Action for 7-8 years and have not seen any “unique” phytotoxicity associated with that product compared to chlorothalonil itself.

Having said that, we have seen phytotoxicity (thinning and bleaching of foliage with chlorothalonil products in general) at very close spacings and high rates on greens height annual bluegrass when applied during the summer. We ran an experiment last year and were trying to keep anthracnose out without using a penetrant fungicide that might affect turf physiology. We noticed phytotoxicity after 8 weekly applications of Daconil Ultrex 82.5WDG @ 5 OZ/1,000 SQ FT. This is way off the label rate, so it did not surprise me to see toxicity during hot weather. However, I have not seen phytotoxicity with Daconil Ultrex,  Daconil Action, or any other product containing chlorothalonil at labeled rates or recommended intervals, especially if these products are alternated with other chemistries as we recommend.

The take home message is that turf mangers should keep the rates of any fungicides within label specifications, take mix and alternate chemistries to improve disease control, reduce the possibility of resistance and to prevent phytoxicity.  Finally, avoid spraying any fungicide during the heat of the day.

Bacterial Decline of Creeping Bentgrass

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A golf course lawn.

Several golf courses in the tri-state area have reported symptoms of etiolation and decline of creeping bentgrass putting greens.   In some cases, the etiolation has occurred in isolated areas and then disappeared, but in other situations etiolation has progressed into a gradual decline of affected turf.  Patches can range from 1 to several inches in diameter and may coalesce into large areas of blighted turf.   Repeated isolations has yielded a number of bacterial species including Acidovorax and infected turf has often exhibited pronounced bacterial streaming from cut leaf tissue.  Annual bluegrass on these greens has been unaffected by this problem.

Declining Bentgrass.
Slow growth of turf can be due to many factors but cool dry weather has been important this spring.

Although little is known about the etiology and control of etiolation and bacterial decline of turf, it appears to be stress related with the recent heat wave acerbating the problem.   Anecdotal evidence from superintendents who have combated etiolation and decline suggests that recovery is encouraged by: (1) raising the height of cut, switching from heavy to light weight mowers, reducing rolling (not mowing) frequency, and using solid rollers on mowers, (2) hand syringing to avoid soil moisture extremes (particularly drought stress), (3) stopping the use of vegetative plant growth regulators (such as Primo) or reducing the rate and/or increasing the interval between applications, (4)  avoiding the use of ammoniacal fertilizers (e.g., ammonium sulfate) in favor of nitrate-based sources during symptom expression, (5) avoiding heavy topdressing applications during hot weather (> 90°F) and dispersing bunker sand on greens each day (e.g., with a back pack blower prior to mowing), (6) delaying aerification, spiking, or other cultivation practices until the problem subsides, (7) reducing shade, and (8) improving air circulation around greens to reduce the leaf wetness period.

Currently, there do not appear to be any really effective chemical treatments for the control of etiolation and bacterial decline on bentgrass.  Junction and other copper-based fungicides have provided limited control and can burn turf during hot weather.  In some cases, Daconil Action has increased the quality of affected turf, but has not provided outstanding control of bacterial decline.  Antibiotics (e.g., Mycoshield) have given little suppression of outbreaks during hot weather, can be very phytotoxic, and are not labeled for use on turf.  ZeroTol (a surface disinfestant) has appeared to reduce symptom severity on some courses when applied every 2 to 4 days, but has not controlled bacterial infections.  Until more research is conducted on this emerging problem, the best course of action is to reduce plant stress and avoid practices that cause excessive wounding of turf, particularly during periods of environmental stress.

Crabgrass Continues to Emerge

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Recent rains have stimulated more crabgrass to emerge. This will probably continue through the end of the month. If applied preemergence herbicides, especially early in the spring, you may start to see “breakthrough”. If have decided to control crabgrass postemergence (manually or with postemergence herbicides), you should scout for emerging plants after each rain or irrigation event. Water will stimulate more emergence of plants. See previous post for more information.

Recently emerged crabgrass seedling plants (taken 20 July).
Recently emerged crabgrass seedling plants (taken 20 July).

Dormancy vs Death

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The question of the day is… How do I know whether the grass that is losing its green color is going dormant or going to die? It isn’t always easy to tell but here are some clues that can help.

First, asses the uniformity of the grass. Is all of the grass turning brown or straw colored? Or… is the grass turning brown in spots or small patches? If the browning is occurring in spots or small patches, there is a good chance the grass plants in those spots are dying, especially if this occurs in a matter of hours to a couple days. [Read more…] about Dormancy vs Death

Crabgrass Emerging

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Crabgrass growing on top of lawnI have been observing the emergence of crabgrass since late April (see image above). Some crabgrass has now entered the tillering stage of growth.

As a general rule, most people begin to notice crabgrass in turf around the 4th of July (Independence Day). At that time, the crabgrass plants are large enough that the leaves stick-up above the desired grasses and the lighter (yellow) green color is highly noticeable from a distance. However, the crabgrass plants will be relatively large (tillered) by that date.

For those that want to control crabgrass postemergence, the next few weeks is the time for action because, regardless of the control tactic, crabgrass becomes more difficult to remove as it matures (get larger).

For those interested in non-chemical options, hand-picking the crabgrass is easiest when the plant are relatively small seedlings. As the plants grow, the enlarged root system makes it more difficult to pull these plants without snapping off the leaves and leaving the crown attached to roots. If this happens, the plants will re-grows its leaves. Hand-picking crabgrass plants is only practical for small turf/lawn areas.

There is limited detailed information the application and efficacy of “organic” herbicides to control crabgrass postemergence. So specific recommendations, other than make treatments to small plants, are not available.

For those interested in conventional postemergence herbicides, these are most effective when applied to seedling crabgrass plants. Two, sometimes more, treatments are often needed, especially when crabgrass plants are relatively large. Apply at 7-to 10-day intervals. Do not apply to drought stressed plants. Discoloration may occur on the desired turfgrass after the treatment is applied. Discoloration is generally more noticeable if the grass is under stress from heat or drought. Spraying the herbicides will be more effective than applying as a granular product. Do not irrigate for 24 hours after the appliation and do not apply if rain is forecast within 24 hours after the application.

Herbicides with postemergence activity on crabgrass that is less than the 4-tiller growth stage include: quinclorac (Drive, SquareOne ), mesotrione (Tenacity), and fenoxaprop (Acclaim Extra). Dithiopyr (Dimension) is primarily used as a preemergence herbicide but it does have postemergence activity on crabgrass plants in the 1- to 4-leaf growth stage.

The use rates and tolerance of desired turfgrasses varies among these herbicides, so consult the label for specific use information. You can also read more at: Crabgras and Goosegrass Control in Cool Season Turfgrass.