Don’t wait until spring hits to think about how you plan on tackling weeds, pests and disease in your clients’ lawns. Bret Corbett, field research and technical services manager for Prime Source, and Aaron Hathaway, technical field services manager for Nufarm, offer recommendations for fighting some common lawn problems: Poa annua, billbugs and dollar spot. With all chemical applications, make sure you follow the product label and PPE guidelines.
Poa annua
Poa annua, or annual bluegrass, is a winter annual weed, meaning that it germinates in the fall. Most of the time, the fall germinations go unnoticed until late winter or early spring. This is due to shorter day length along with colder soil temperatures, which keep the annual bluegrass in a semidormant state after germination.
When the temperatures warm up, Poa annua will emerge from dormancy and grow rapidly. When temperatures are colder than normal and snowfall is greater than normal, expect to see high weed pressure in the spring. This leads to the infamous seedhead while it is flowering, which makes it very noticeable in the turf canopy, and it can be seen until the summer. When soil temperatures heat up, Poa usually completes its life cycle and dies.
Cultural control: Poa thrives in low-mowed, poorly drained compacted soils. Increasing mowing height, reducing compaction and implementing a proper fertilizer program can decrease annual bluegrass pressure.
Chemical control: A dithiopyr preemergent can be applied late July/early August but would need to be applied each season for better control. For postemergent control, amicarbazone can be applied on Kentucky bluegrass and is best used in the spring or fall season, with two to three applications in one season 14-21 days apart. Plant growth regulators like prohexadione calcium are also an option to regulate Poa growth. For warm-season applications in dormant turf, glufosinate can provide adequate control without causing delays in green-up. Glufosinate can be tank mixed with preemergent herbicides such as prodiamine to provide control of summer annual weeds.
Billbugs
Billbugs are dark charcoal or black insects that are 0.3-0.4 inch in length. They can be found in many different parts of the country and vary in species including hunting billbugs and bluegrass billbugs. They typically overwinter as adults in leaf litter, mulch and thatch.
They emerge in the spring when soil temperatures increase. Since these insects are in a state of suspended development (diapause) during the winter and burrowed into the turf, snowfall and colder temperatures usually have no effect on these insects. However, if cold temperatures persist, it could delay when the insect emerges as the soil temperature has to reach 55 degrees F.
Cultural control: Maintain healthy turf and observe proper fertilization timings and mowing. Other options would be to use less desirable turf types to the insect, such as perennial ryegrass or resistant varieties of bermudagrass or zoysiagrass.
Chemical control: Determine the stage of the insect’s development by using a pitfall trap to catch and assess the insect. It’s important to have an insecticide in the turf in May or late May before the eggs hatch and the larvae start to feed. Clothianidin and pyrethroid insecticides such as bifenthrin, lambda-cyhalothrin or imidacloprid are the recommended chemistries.
Dollar spot
Dollar spot disease can be found in almost every species of turfgrass and presents as spots on the turf approximately the size of a dollar coin (hence the name). The spots are white to light tan in color and can range from 0.5 to 6 inches in diameter. The lesions will begin to appear when night temperatures exceed 50 degrees F. In addition to warmer soil temperatures, the pathogen requires 10 hours of continuous leaf wetness.
Nutrient-deficient turf is more susceptible to dollar spot; however, the disease can also be observed more in stressed situations such as drought or excessive thatch.
Cultural control: Maintain proper nutrient programs, use plant disease-resistant cultivars, increase mowing heights and remove wet leaves.
Chemical control: Azoxystrobin in combination with propiconazole is the most recommended chemistry and provides good to excellent control of dollar spot. Metconazole is another broad-spectrum fungicide that provides good control. Early action is key — once you begin to see spots, make an application.
