Pest & Weed Control
Choose the least amount of the least toxic product when pest or weed problems arise
Choose the least amount of the least toxic product when pest or weed problems arise
While the market offers weed control products with less environmental and health risk than conventional options, managers should still use these products as a last resort. The effectiveness of these alternative products will decrease if not complemented with proper cultural practices covered in earlier toolkit sections. The Bio-Integral Resource Center develops a Directory of Least-Toxic Pest Control Products every couple of years. Other options to evaluate the risk or toxicity of a product includes looking up the signal word or the Environmental Impact Quotient using Cornell University’s calculator. Natural and reduced-risk products to consider for turfgrass weed management include:
Post-emergent Broadleaf Weed Control (Dandelions, clover, ground ivy)
Pre-emergent selective Weed Control
Dr. Paul Koch thinks that “anybody that works in turfgrass will tell you that the healthier the plant system is, the more likely it will fend off weeds, insect pests and diseases.”
According to Dr. Koch, growing healthy turfgrass starts with building healthy soil, selecting the right grass species for the right site and culturally managing the grass properly. Integrated Pest Management fits into these initial steps by focusing on the life cycles of pests and weeds to avoid unnecessary chemical applications.
“Knowing the biology is the greatest challenge with IPM,” Dr. Koch said. “In the old days we used to say it’s April 1st, lets get out our crabgrass pre-emergent. This strategy is ‘easier’ from a standpoint of managing it that way, but it’s not as effective, can cost you money and adds needless inputs into the environment.”
The City of San Francisco follows the Precautionary Principle when determining the health and safety of using a pest or weed control product. If just one respected scientific body designates a product harmful to human or environmental health, the San Francisco Department of the Environment (SF Environment) takes a proactive approach and looks into restricting the product.
Dr. Chris Geiger said the city was surprised when IARC classified Glyphosate as a probable carcinogen, but immediately acted. “We increased the Tier ranking to Tier 1 (most hazardous/restricted) and we started organizing a lot of meetings around this subject to see what could be done to reduce use of glyphosate and what safer alternatives are available.”
Geiger asserted that developing policy around the use and restriction of glyphosate posed a significant challenge to San Francisco. There was temptation to outright ban the product, but the city was concerned the alternatives held higher risks.
“We like to call this regrettable substitution, where something worse is used. That might be an herbicide that’s worse or someone decides to use their weed flamers or gas powered weed whips more than they did in the past which, also, has a cancer risk,” Dr. Geiger explained.
To avoid regrettable substitution, San Francisco enacted glyphosate restrictions for most situations and places where the product was not necessary. The city could not, however, eliminate the product on all areas, particularly in natural areas. Dr. Geiger said the alternatives such as goat grazing and burndowns for controlling invasive species were not effective in challenging habitats such as hillsides. Although the City has refrained from banning Glyphosate, they successfully decreased use of the product by 96% since 2010.
As the second largest landowner in Cook County, IL, the Metropolitan Water Reclamation District of Greater Chicago (MWRD) manages many different landscapes. The MWRD invests a fair amount of time and money to control vegetation on its properties, especially for areas that can't be mowed such as native prairies, water reservoirs with steep slopes and invasive species in tree and fence lines.
"The man hours, whether we are using a contractor or our own resources to control weeds, becomes difficult with the sheer volume of property we own and how scattered the vegetation is throughout our property," said Aruch Poonsapaya.
Poonsapaya attempted to replace these man hours with goat hours in September and October of 2019 at the Lemont Water Reclamation Plant. The MWRD and Poonsapaya learned about goats from grazing programs implemented at both the Chicago O'Hare International Airport and the Downers Grove Park District.
"We reached out to them, saw what they did and decided to do a trail program on our own to see how it fit into our landscape program and philosophy," Poonsapaya explained.
The pilot goat grazing program met expectations. Vegetation Solutions, a company based in Richland Center, WI, rented 50 goats and sheep to the MWRD to eat and knock-down vegetation on five acres over five to six weeks for a little less than $10,000. The MWRD directed the goats to graze difficult to cut and mow spaces such as tree lines and native prairies.
"They'll eat anything that they can reach, anything four or five feet off the ground," said Poonsapaya. "They'll eat through the buckthorn and other vegetation. They're eating machines."
The goats proved to be low maintenance. The MWRD provided the goats with water, while the Vegetation Solutions owner visited the site one or two days a week to check on the health of the goats and feed them minerals. The goats completed their diet by eating vegetation on the site.
Poonsapaya looks forward to witnessing the long-term results of this program. "Talking to past goat users, the more you treat with goats, the vegetation doesn't come back as dense or as overgrown the next season."
White grubs are the most common insect pests on lawn and sports turf. Effective grub control relies on understanding the different grub species and their life cycles. The most common grub species found in the Midwest are Japanese beetles or chafers. Both grub species will cause limited damage to turfgrass if populations do not exceed five grubs per square foot. If populations exceed that threshold, first identify the type of grub and then tailor a control strategy for the grub species:
Control for Japanese beetles
Adult Japanese beetles emerge from the ground between late June and early August. Most curative organic and conventional grub control products are ineffective before and during this time period. For best results, apply control strategies during late August and early September when the adult beetles lay eggs. Refraining from irrigation may reduce populations as the eggs desiccate under drought conditions. If the season experiences frequent rains, than resort to OMRI certified products of beneficial nematodes, milky spore or Grandevo.
Control for chafers
Chafers have similar life cycles to Japanese beetles. Unlike Japanese beetles, however, chafer eggs do not dessicate and their larva/grubs excel in dry conditions. Well irrigated fields will allow turf roots to replenish and handle most chafer pressure. Beneficial nematodes and Grandevo will control for chafers in August and September. Milky spore will not work on chafers.
While numerous diseases can occur on lawn or sports turf, they rarely lead to extensive plant death and hence rarely require fungicide applications. Follow all proper cultural practices to limit conditions that are optimal for disease development. If disease does occur, it often recovers on its own once the favorable disease conditions have passed.
Dr. Doug Richmond recommends first assessing soil health to help grow healthy plants capable of defending themselves from insects or recovering quickly from pest damage. A healthy soil features a diverse community of soil invertebrates and microbes that promote carbon and nitrogen cycling, and a nutrient profile that ensures adequate plant nutrition. Combining healthy soil with proper cultural, biological and chemical IPM controls can reduce insect pest populations and improve plant resistance to insect pests.
“That’s the framework within which we are implementing IPM,” Dr. Richmond elaborated. “When we talk about insects in particular, the way we organize insects, based on behavior, taxonomy and life cycles, dictates how we manage them.”
Multiple cultivars of perennial ryegrass, tall fescues and fine fescues can contain endophytes that produce defensive compounds that deter or poison insects. However, these defensive compounds only affect above-ground insects such as cutworms, sod webworms, armyworms, chinch bugs and billbug adults. Grasses with deep fibrous root systems, such as tall fescue, seem to better resist damage from below ground insects like white grubs and billbug larvae. These grasses, also, better tolerate stress and drought. The National Turfgrass Evaluation Program collects and shares open-access performance data of turfgrasses by region to help field managers choose mixes that best resist insect pest pressure.
Multiple biological and reduced-risk products effectively control insect pests, but only if applied during the appropriate time of the respective insect’s life cycle. Parasitic nematodes infect and kill insects, reproduce inside the host insects' body and spread to other insects. GrubGone and Acelepryn can control white grubs, whereas Spinosad and Acelepryn will control caterpillars.
“We have a hard time in some areas of our native plant garden to establish plants, because there is nothing to hold the roots in the top several centimeters,” Bradley Herrick described conditions at the UW-Madison Arboretum. “Invasive Jumping Worm species can fundamentally change the structure of soil.”
A high abundance of jumping worms can dry out the soil and destroy vegetation by creating too much pore space and leaving large castings resulting in highly erodible soil.
Compared to common earthworms found in the soil, jumping worms have longer (7-20 cm), darker and more rigid bodies, do not burrow into the soil during the winter and overwinter in a cocoon. Both the location of the milky-white clitellum near the jumping worm’s head and the jumping worm’s violent and active movements when poked or disturbed best distinguish it from common earthworms. Finally, they produce "Coffee grounds" casts and lose their tail when handled roughly.
Herrick says educating yourself and others to identify jumping worm before they establish and spread will best control this new soil invader, “There’s nothing perfect in terms of what we can do to prevent the introduction or spread of any invasive species, particularly jumping worms. Having the knowledge to know what to look for and what to ask, we can do our best to minimize their spread.”
Only use, sell, plant, purchase or trade landscaping and gardening materials and plants that appear free of jumping worms. Ensure compost reaches 104 degrees F to reduce cocoons. Clean soil and debris from vehicles, equipment and personal gear before moving to and from a work or recreational area.
Most products to control jumping worms are new. An entomopathogenic fungal isolate of Beauvaria bassiana has show to reduce adult jumping worm populations by 70%. Some research exists for the effectiveness of biochar. Consider reducing wood mulch applied in your garden and experiment with pine needles, hay or native grass mulch to repel the worms or solarization to kill cocoons.