How can herbicide damage to golf turf be prevented?
The selectivity of herbicides is relative and conditional; if applied improperly, any herbicide can potentially harm turf. I. Symptoms and causes of herbicide damage. Herbicide damage is divided into acute damage and chronic damage. Acute damage is caused by contact herbicides, appears quickly, and the affected turf blades show brown...
The selectivity of herbicides is relative and conditional; if applied improperly, any herbicide can potentially harm turf.
I. Symptoms and causes of damage
Herbicide damage is divided into acute damage and chronic damage. Acute damage is caused by contact herbicides, develops quickly, and the affected turf blades show brown spots, curling, and fading. Chronic damage is caused by systemic-conductive herbicides, manifesting as slow turf growth, then gradual yellowing, and in severe cases slow death. The causes of herbicide damage to golf turf include:
1. Improper application: Herbicides are dosed by the amount applied per unit area rather than by concentration. Not understanding herbicide application technology, using the wrong herbicide, or using the wrong amount can all harm turf. Inaccurate control of spray volume and uneven spraying are both forms of improper application. Using a mist blower to spray turf herbicides produces mist with a strong impact force on the turf leaf surface, causing the herbicide to cling to the turf leaf surface and produce phytotoxicity. If the temperature of the spray solution in the sprayer tank exceeds 42°C, it may also harm turf.
2. Improper maintenance and management: The application of most turf herbicides such as Turf Grass Ning No. 1, No. 38, and No. 42 all require irrigation with water for 15 to 20 minutes 40 minutes after spraying, which can minimize the absorption of the herbicide by the turf leaf surface. If the ground is not leveled before laying turf, spraying herbicides may damage turf in low-lying areas. Spraying herbicides on turf with very high grass, a thick thatch layer, and no mowing can easily cause phytotoxicity to turf. Immediately after spraying herbicides, cutting, aerating, spiking, etc. will damage the turf root system and cause turf yellowing. After spraying, machinery rolling causes the herbicide to cling to and come into closer contact with turf blades through the wheels, increasing the amount of herbicide absorbed by turf, while also reducing air permeability in the turf root zone and harming turf. If golfers enter the green from an area just sprayed with herbicide, it may damage the green turf.
3. Abnormal climate or poor turf growth conditions: Disastrous weather such as high temperatures, cold waves, drought, hail, flooding, and frost causes abnormal turf growth. If herbicides are sprayed at such times, the herbicide absorbed by turf cannot be degraded and can easily harm turf. In early spring, when temperatures are unstable, applying herbicides when the daily temperature drops by more than 12°C or when early spring frost strikes suddenly can cause damage to turf. Applying herbicides when the temperature exceeds 33°C may also produce phytotoxicity.
II. Prevention and rescue of phytotoxicity. 1. Strategies to prevent possible phytotoxicity: (1) Choose pre-emergence weed control. Using herbicides before emergence to prevent weeds only requires application at the normal rate; if control is carried out after weeds have emerged or when damage is severe, the herbicide rate must be increased, raising the risk of phytotoxicity to turf. (2) Adhere to safe operation. Operators should clearly understand the herbicide application technology before spraying, adjust the spray machinery, calculate the dosage accurately, and operate according to the plan. (3) Maintain robust turf. Obtaining robust turf through proper maintenance improves turf adaptability to adverse conditions and can reduce the risk of herbicide phytotoxicity. Low mowing, reducing the thatch layer, and regular aerating and cutting can improve the air permeability of the turf substrate, increase turf root vitality, and reduce the side effects of herbicides on turf. (4) Apply low doses multiple times. For older weeds that have passed the suitable control period, use continuous low-dose multiple applications to avoid damage to turf caused by a single high-dose application. Low-dose multiple applications can partially injure weeds and achieve 60% to 70% weed control; after 2 to 3 consecutive applications, the weeds become increasingly damaged, placing them at a disadvantage in competition with turf, and their space is gradually occupied by turf. (5) Alternate and mix applications. Reduced-rate mixtures of turf herbicides with different mechanisms of action can reduce possible phytotoxicity to turf.
2. Measures to prevent possible phytotoxicity: (1) Strictly control the dosage. Precisely test the walking speed of machinery or manual spraying; before preparing the spray solution, repeatedly check to confirm there is no error before implementation, avoiding discrepancies. (2) Ensure machinery is in good condition. The use of mist blowers for spraying turf herbicides is prohibited. Before spraying with large sprayers, strictly inspect and maintain them to ensure they are in good condition. Thoroughly test the spray equipment, train operators by test-spraying with clean water, and prepare the spray solution using the "two-stage dilution method." After preparing the solution, rinse the machine tires with clean water to prevent wheels carrying herbicide from rolling over turf. Eliminate machine leakage. Mark clearly to prevent overlapping or missed spraying. (3) Avoid adverse weather. For herbicide application in transitional turf zones in spring, spray before the arrival of cold waves. To improve turf resistance to harsh environments during green-up, apply overwintering fertilizer with a relatively high potassium ratio in September to October to protect healthy overwintering of turf. Do not use herbicides during drought, frost, or pest outbreaks. Spray at temperatures of 15°C to 33°C. When the temperature is above 33°C, reduce the rate appropriately. (4) Exercise strict management control. When spraying herbicides for soil treatment or with both pre-emergence and post-emergence herbicidal action, irrigate with water for 15 to 20 minutes 40 minutes after spraying, and the irrigation should soak through. When spraying certain herbicides with both pre-emergence soil treatment action and post-emergence foliar action, such as Turf Grass Ning No. 52, No. 75, No. 18, and No. 35, not only should water be applied for 15 to 20 minutes 40 minutes after spraying, but water should also be applied for 5 to 6 minutes before spraying, which can reduce the amount of herbicide absorbed by turf blades. When irrigating above slopes, use "small amounts multiple times" to prevent the herbicide above the slope from being washed down to sensitive turf or tree roots below. Avoid
fertilizing or spraying other insecticides or fungicides within about one week of herbicide application. Mow low frequently to cultivate robust turf with strong root vitality. For turf that has been planted for many years and has too thick a thatch layer, cut, aerate, and spike to break up the thatch layer and increase turf root air permeability. These tasks need to be carried out one month before herbicide spraying to prevent phytotoxicity. Avoid rolling after spraying. (5) Set up isolation belts. When overseeding fairways with cool-season turfgrasses such as perennial ryegrass, Turf Grass Ning No. 1 + No. 42 or Turf Grass Ning No. 1 + No. 18 can be sprayed at the same time as overseeding or within 3 days before or after. To prevent the herbicide from being washed onto the fairway and damaging ryegrass when irrigating after spraying in the rough, spread a 20 to 30 cm wide strip of activated carbon at the junction between the rough and the fairway. Mix 1 part industrial activated carbon with 5 parts sand evenly, and spread two rows with a topdressing machine, or spread by hand. This is especially important at junctions where the rough is higher than the fairway.
3. Rescue of possible phytotoxicity: If slight herbicide phytotoxicity occurs on turf and the turf turns yellow, spray turf root-promoting and green-keeping agent as soon as possible, with an application rate of 0.03 ml/sq m, diluted with 120 ml/sq m of water, and spray 3 times consecutively. Alternatively, as early as possible, spread sand mixed with industrial activated carbon on the affected turf to adsorb the mistakenly sprayed herbicide and reduce the harm. When phytotoxicity is slight, spray low-concentration foliar nitrogen fertilizer or potassium dihydrogen phosphate at a concentration of 35% to 40% of the usual amount.
The key to successful rescue from turf herbicide phytotoxicity is to take remedial measures within 48 hours after discovering misuse, and the earlier the timing, the better the effect.