Coping with Late Season Drought in Turf – Turfgrass Science at Purdue University

Coping with Late Season Drought in Turf

(Adapted from the Midwest Regional Turf Foundation Factsheet, Oct 1, 2004)
After an extremely wet summer, turf drought stress has come out of nowhere almost throughout the state after a dry August and September. Though September and October are prime growing months, turf will not recover unless the turf receives ample rain or irrigation soon. If your turf areas receive ample rainfall and/or irrigation in the very near future, fall management practices can occur as normal. However, limited rain or irrigation may have far-reaching effects on our turf this fall.

Fertilization
Though September is the most important time to fertilize, fertilizing drought-stricken turf is not recommended because the plant will not take up nitrogen quickly if at all. Therefore, avoid fertilizing drought-stricken turf until it has greened-up, hopefully sometime in early October. On normal years, most turf should receive about 2-2.25 lbs N/1000 ft2 in the fall with 1.0 lb N/1000 ft2 applied in September and 1.0-1.25 lbs N/1000 ft2 applied near the final mowing in early November. If you haven’t applied the September fertilizer yet, wait until the turf has greened up and apply 1.0 lb N/1000 ft2 in October with mostly fast release N. Then the November application can be made at 1.0-1.25 lbs N/1000 ft2 with fast release N near the final mowing. If that sequence doesn’t fit into the schedule, a second, much less-desirable method would include applying a fertilizer now that has the majority of nitrogen (60-70%) as slowly available water soluble, banking on the nitrogen releasing later after rains return. Then apply the November application as is normal. This method is less desirable because it applies nitrogen when it cannot be immediately used by the plant, which might increase the chances of off-target movement (through leaching or volatility).

Broadleaf Weed Control
Broadleaf herbicides will not effectively control drought-stressed weeds and may damage drought-stressed turf. Higher rates, adjuvants, and/or using different products (spiking the tankmix) will not increase control on drought-stressed weeds. You’re better off waiting to apply any broadleaf herbicide applications until the rains return. Since broadleaf weed herbicides can be effective when applied well into October and early November, you should have plenty of time to apply yet this year, which will be far more effective than applications next spring.

Grub Damage and Control
Though we initially did not expect widespread grub damage this year, this drought has changed everything. Since adult Japanese beetles and masked chafers prefer to lay eggs in irrigated turf, egg-laying occurred in almost all turf areas this summer. Had rains continued, the relatively widespread but low populations would not have caused serious damage. However, drought stressed turf cannot withstand even minor feeding from relatively low populations of grubs and thus grub damage is now widespread. Unfortunately, much of the grub damage is going undetected because it is being mistaken for drought damage. If your turf is suffering from grub damage, Dylox is currently the insecticide of choice, but don’t expect 100% control given the current maturity of the grubs. To maximize control, be sure to water it in thoroughly and control may be especially difficult in thatchy turf. Since it may take 7-14 days for the grubs to die after application, don’t get in a hurry to apply a second application thinking the first didn’t work. Unfortunately, we are at the end of the window for using Dylox because the grub feeding should be winding down shortly. Insecticide applications can only be used to slow down grub damage in turf. Insecticide applications made now will not bring our damaged turf back to life, nor will an insecticide application affect grub populations next year.

Aerification
Now is prime time to aerify turf areas, but it is impossible for tines to penetrate drougthy soils and drought-stricken turf cannot recover from aerification. However, on higher mowed turf like lawns, roughs, and even athletic fields, aerification well into November will still reduce compaction with minimal negative effects. We’d much prefer aerifying in September or early October to allow turf recovery and minimize winter dessication or encroachment from winter annual weeds. The higher mowing heights of lawns, roughs, and athletic fields protect the plant crowns from winter dessication around the aerification holes, but this is not the case on greens and fairways.

Seeding
Seeding done earlier this fall likely have not germinated unless under irrigation. Rains will hopefully return soon, allowing seeds to germinate in unirrigated areas and seedlings to mature before winter. In the worst case, seedlings will germinate but not mature before winter, succumbing to winter injury. This could be the case with tall fescue and perennial ryegrass, which are the most susceptible to winterkill. Seeding now (the first week of October) will likely not allow seedlings to mature before winter even if irrigation is applied. Therefore, wait to dormant seed until after Thanksgiving or wait until spring to seed. Other options include using a nurse grass like annual ryegrass on erodable areas and germination blankets can also be used to extend the seeding window for a couple of more weeks. Sod is another option and this can be used almost throughout the winter as long as the soil is unfrozen and water can be applied during the winter to minimize the risk of desiccation.

Conditions change quickly at this time of the year. An early- or late-arriving winter, rainfall, etc., can dramatically change turf management practices. Stay tuned to Turf Tips at www.agry.purdue.edu/turf for the latest updates and recommendations.


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