NYSTA
Calendar of Events
SUNY Delhi/ NYSTA Golf Seminar & Outing
SUNY Delhi, Delhi, NY
June
5, 2012
Winning Fields Seminar
SUNY Fredonia, Fredonia, NY
June
12, 2012
CNYGCSA "Go Over the Research"
Cornell University, Ithaca, NY
June
21, 2012
Contact Dick Perry at 315-673-4000 for more information.
Sullivan County Challenge -Steve Smith Memorial Tournament
Grossinger Golf and Country Club, Liberty, NY
August
22, 2012
Northeastern Golf Course Superintendents Association POA Annua Golf Tournament
Glens Falls Country Club, Glens Falls, NY
September
24, 2012
Hahn
Memorial Scholarship Tournament
Shadow Lake Golf Course, Penfield, NY
October
1, 2012
Turf & Grounds Exposition
Rochester Riverside Convention Center, Rochester, NY
November
13-15, 2012 / Sponsored by Grassland Equipment and Irrigation Corp., Inc.
Straying Off Target: Turf Insecticides Impact Arthropod Communities, But Do We Need to Care?
Daniel C. Peck, Ph.D., EntomoTech Fundamentals
Spray, squish or bury them, every tactic used to control insect pests will cause collateral damage. The salient question is not whether such impacts occur, but whether they are relevant enough that we need to care. Until unintended consequences are exposed, however, they cannot be taken into account for cost-benefit analyses, such as weighing the obvious benefits of protecting turf from injurious insect pests against the economic, environmental and ecological costs of intervention.
Herein is a discussion of results from a series of studies on the nature and relevance of non-target effects posed by the insecticidal control of white grub pests in cool-season turf. Results from these field experiments, all conducted in an experimental low-maintenance home lawn in western NY, support five concepts that highlight why pest management practitioners should remain motivated to adopt reduced-risk approaches to plant protection.
1. Turfgrass harbors an abundant and diverse assemblage of arthropods.
While the average home owner might be loath to know, underfoot are countless micro-denizens that dismiss the notion of turfgrass as an “ecological wasteland” or a “green desert.” One way to expose this animal community is to extract it from soil cores using a Tullgren funnel, which is a device that forces mobile arthropods into a collection vessel through a combination of uncomfortable exposure to light, desiccation and high temperatures. Another way is to set pitfall traps, which capture arthropods moving across the surface after they tumble into the collection container. Each technique measures a distinct animal community, namely soil-active (soil extraction) and surface-active (pitfalls) arthropods.
Using these techniques, our studies revealed 700-2500 arthropods per square foot of turf and associated topsoil. In soil cores, the most represented groups were mites, comprising 67.8% of total individuals, followed by springtails (17.5%), ants (6.5), true bugs (3.6) and thrips (1.1). Considering the entirety of the catch, there were 6 taxonomic classes of arthropods and 10 orders of insects represented. In contrast, the most collected groups in pitfall traps were sowbugs and pillbugs (37.2%), followed by daddy longlegs (19.2%), other spiders (19.0%), crickets (15.0%), ants (6.1%) and beetles (3.6%), for a total of 5 classes of arthropods and 7 orders of insects represented. When we examined the springtails in more detail, we found 22 species, which is similar to the diversity reported in natural grassland systems.
2. Those arthropods work to promote the sustainability and health of turfgrass.
Diversity aside, just based on sheer numbers alone this fauna should be expected to have some role in how the ecosystem functions. We should moreover expect a greater role because they benefit from inhabiting a perennial system. In contrast to annual production systems, the arthropod community in turfgrass does not experience their world ripped out by the roots each year. One beneficial role is the regulation of pest populations. This occurs through predation and parasitism of the pest species. Another role is nutrient cycling, such as through the degradation of thatch and plant tissue, and the facilitation of microbial decomposition. A lesser appreciated role is soil structure improvement. The movement of larger arthropods through the soil has a positive effect on soil macrostructure while the breakdown of fecal pellets from soil arthropods of any size improves soil microstructure. Behind the scenes and beneath our feet, this fauna helps us in various ways to promote healthy turf.
3. Insecticides can inadvertently suppress those arthropods.
Active ingredient, mode of exposure, formulation and application method are all relevant to the breadth of insects affected by a control product. All else being equal, broad-spectrum contact insecticides will affect more non-target groups than narrow-spectrum systemic insecticides. In the past, control programs featuring older generation insecticides such as carbamates and organophosphates have been shown to halve the size of predator and decomposer communities in turf.
In our three-year study to contrast the effects of different white grub control regimes on soil arthropod communities, the organophosphate trichlorfon had no measurable impact. This was unexpected because of its classification as a broad-spectrum contact insecticide with a role in fast-acting late season grub control. No impact was detected for halofenozide (an insect growth regulator) or entomopathogenic nematodes (a biological control). The only discernible impacts were attributed to imidacloprid, a long-residual systemic neonicotinoid. This was measured through soil core extractions over the course of two consecutive seasons where imidacloprid was applied once a year. Compared to untreated plots, overall populations of insects declined by 54%. The specific groups significantly affected were springtails, beetles and thrips (58-62% reduction).
We focused on imidacloprid in a second experiment designed to test the persistence of abundance effects over 6 years of annual applications. This scenario matches that of many turf protection programs, namely the yearly application of preventive insecticides. Pitfall traps were added to measure impacts on the surface-active community, but there was no response detected in that fauna. As measured by soil core extractions, however, imidacloprid’s suppression of certain groups persisted over all 6 years. Therefore there may be a diverging response of soil- and surface- active fauna to the nontarget impacts of imidacloprid. Among the beetles, impact was expressed in adults (but not larvae), and in ground beetles and rove beetles (but not leaf beetles or weevils). The suppression of predaceous (but not plant-feeding) beetles indicates an indirect effect brought on by declines in prey populations, such as springtails. Systemicity is a favorable attribute in an insecticide because the mode of exposure is narrowed to ingestion rather than contact. This may be countered, however, by imidacloprid’s long residual activity, which could broaden nontarget effects through time and into the microarthropod community.
4. Insecticides can inadvertently suppress those arthropods and thereby sustainability.
If insecticides impact the abundance and diversity of nontargets, they may also affect the function of those nontargets. For instance, if predaceous beetles are suppressed by imidacloprid, then their role as beneficial predators of insect pests might be suppressed. We thereby studied the short-term effects of imidacloprid and related insecticides on the role of nontarget arthropods, namely predation on Japanese beetle eggs. Eggs were implanted into experimental field plots treated with four neonicotinoid insecticides. Recovered 2 days later, we measured their loss (or rate of “predation”) with respect to insecticide, and over a period of 1, 2, 3 and 4 weeks after application. Under the conditions of this study, a single application of neonicotinoid insecticide does temporarily disrupt egg predation. Egg loss declined 28-76% in plots treated with imidacloprid. The effects were detected as soon as 1 week after treatment and persisted as long as 4 weeks. The degree of suppression did not vary across season, or whether applications were made in June, July or August. Moreover, clothianidin, dinotefuran and thiamethoxam exhibited a similar effect.
When a preventive insecticide is applied at the time of egg laying, its intended effects (death to newly hatched grubs) may be in conflict with unintended effects (disruption of egg predation). Although compromised by early season intervention, the biological control services provided by generalist predators of white grubs might be conserved through later season intervention.
5. The balance between intended and unintended impacts should be explicitly examined.
Once exposed, it may be that nontarget impacts are not relevant enough to matter. But until exposed, they cannot be taken into account in cost-benefit analyses. Every pest management tactic inevitably impacts the overall biological community and has unintended consequences. In white grub control programs, for instance, the desired effects of the technology (such as neonicotinoid insecticides) must be weighed against those of the practices it can potentially supplant (such as carbamate and organophosphate insecticides). Preventive insecticides have enormous benefits for plant protection because they avert white grub outbreaks. There is currently an overwhelming reliance on this approach, often coupled with repeated yearly applications. As brought to light in our studies, the benefit can now be weighed against ecological costs that were previously unrecognized: suppression of springtails may decrease their role in nutrient cycling and conservation of predaceous beetles, in turn exasperating thatch problems and improving the success of white grub eggs and young larvae.
Until the nature and relevance of nontarget impacts from insect control programs are exposed, we should be motivated to select, develop and promote reduced-risk approaches. Cost and formulation are core concerns for insecticide selection, but other attributes to consider include environmental impact quotient, rate of active ingredient, broad vs. narrow spectrum, short vs. long residual, systemic vs. contact action and preventive vs. curative timing.
Original article reprinted with permission from the Landsculptor® Magazine (Feb. 2012), a publication of the Michigan Green Industry Association, .
Sponsored by Grassland Equipment and Irrigation Corp., Inc.
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