such as Mach 2 insecticide are considered biorational products
because they mimic natural substances. Molting is the process
of losing skin.
laws may limit the use of many traditional turf chemicals.
natural substances and organisms fall under the category of
pesticides are third-generation pesticides that are
environmentally sound and closely resemble or are identical to
chemicals produced in nature.
now, anyone who uses pesticides should be familiar with the Food
Quality Protection Act (FQPA), a U.S. law enacted in 1996. The
law's primary goal is to reduce the risk of human exposure to
pesticides to acceptable levels while preserving critical
pesticide uses (2). All currently registered pesticides must
eventually (based on a time-line determined by the EPA) undergo a
Ultimately, decisions made under
the FQPA will have a major impact on the number of products
available for use on turf, and many of the most commonly used
products could be lost (1).
In response, many chemical
manufactures have decided to develop and market alternative or new
pest-control products that are "softer," or pose less
potential risk to humans and the environment. These alternative
products include biorational pesticides or biopesticides, as well
as some novel chemicals with substantially lower use rates.
What is a
The terms biorational
pesticide and biopesticide are rapidly gaining popularity in the
current climate of environmental awareness and public concern (3).
These terms are derived from two words, biological and rational,
referring to pesticides of natural origin that have limited or no
adverse effects on the environment or beneficial organisms (4).
There is, however, actually no
legally clear, absolute definition of a biorational pesticide. The
EPA considers biorational pesticides to have different modes of
action than conventional or traditional pesticides, with greater
selectivity and considerably lower risks to humans, wildlife and
A biorational pesticide is derived
from a variety of biological sources, including bacteria, viruses,
fungi and protozoa, as well as chemical analogues of naturally
occurring biochemicals such as pheromones and insect growth
regulators (IGRs). They are considered third-generation pesticides
that are environmentally sound and closely resemble or are
identical to chemicals produced by insects and plants (4).
Biorational products are quite
different from conventional, broad-spectrum products. They do not
control pests in the same way as most broad-spectrum products.
They are typically target-specific and have little to no impact on
Most biorational insecticides are
much more effective against some insect pests than others. As a
result, proper identification of a target insect pest is
essential. Turfgrass managers must also understand both the
limitations and strengths of biorational products.
For example, many biorational
insecticides have relatively short residual activity compared with
conventional products. Thus, biorational products must be applied
when the pest is in its most vulnerable life stage. Otherwise,
applications may be ineffective, and applications of a
conventional product may be necessary.
visble here as tiny white worms feeding inside a white grup's
carcass, offer an alternative to chemical insecticides.
Biorational insecticides are
classified into two distinct groups: biochemical and microbial.
Biochemical products include hormones, enzymes, pheromones and
natural insect and plant growth regulators. Microbial products
originate from biological organisms such as bacteria, fungi,
nematodes, protozoa and viruses.
Insect pheromones are
chemical substances that are given off by insects and cause a
specific reaction upon reception by another insect of the same
species. Releaser pheromones are fast-acting and are used by
insects for sexual attraction, aggregation, dispersion,
oviposition (egg laying) and alarm or warning. Primer pheromones
are slow-acting and cause gradual changes in growth and
development. Of these types of pheromones, sexual attraction
pheromones offer the greatest potential for insect control.
There are four primary uses for
sex pheromones in present insect-control programs: male trapping,
movement monitoring, detection and population monitoring, and
In turf, sex pheromones are used
in traps to detect and monitor Japanese beetle populations.
However, traps are not effective in controlling this pest. Each
use of sex pheromones offers its own limitations and benefits.
Insect growth regulators
(IGRs) are chemical compounds that alter the growth and
development of insects. IGRs disrupt an insect's growth and
development in two basic ways: as juvenile hormones and as chitin
Juvenile hormones prevent insects
from maturing; they force an insect to remain in its juvenile life
stage (immature, caterpillar or grub stage). Juvenile hormones are
not effective in controlling turfgrass insect pests such as
armyworm (Pseudaletia unipuncta) larvae, cutworm larvae,
sod webworm (Crambus teterellus) larvae or white grubs
because the juvenile is the damaging life stage of these pests.
Much of the exterior (skin) and
even some of the internal parts of an insect are constructed of
chitin (a polymer). Chitin synthesis products inhibit the
production of chitin, resulting in the inability of an insect to
produce new exoskeletons (skin). And, without an exoskeleton,
insects cannot survive. A chitin synthesis inhibitor would be an
appropriate control product for the turfgrass insect pests
(Bt) is a spore-forming bacterium that produces toxins that, after
ingestion, cause a rapid gut paralysis and death of certain
insects, especially caterpillars. Bt is a naturally occurring soil
bacterium, but chemical manufacturers have developed a process to
formulate it and make it commercially available to turfgrass
Bt complements many
environmentally sensitive pest management programs because of its
low toxicity. As a result, Bt is the most widely used microbial
insecticide in the turfgrass and ornamental markets (3). However,
Bt is not a "silver-bullet;" like all control products,
it has limitations. Bt has a relatively short-residual activity;
is readily degraded by direct sunlight; has slow action,
limited-contact activity; and is unable to kill larger larvae.
Success with Bt depends on close monitoring and application when
insects are small or in their most vulnerable life stage.
is a spore-forming bacterium, the causal agent of milky disease in
white grubs of the Japanese beetle and other scarab beetles.
Several strains of milky disease bacteria infect various species
of white grubs; each strain tends to be specific for that type of
grub (3). The bacteria are harmless to earthworms, wildlife and
humans, as well as beneficial insects. Like Bt, milky disease
spores have been formulated and marketed. It was available under
the trade names Doom and Japidemic, and now it is again being
marketed under the trade name Milky Spore.
Milky disease also has
limitations. It is very slow-acting -- even under ideal conditions
it takes several years for the pathogen to provide adequate
control of grub populations. In addition, milky spore disease is
relatively expensive, and much of the research data on this
product has shown an extremely variable pattern of performance
is a naturally occurring fungus that infects several insects.
Spores of the fungus adhere to the insect skin and upon
germination, penetrate the body wall, eventually killing the
insect. Beauvaria bassiana has limitations as well:
Similar to other fungi, it typically requires hot, moist
conditions to be effective. More research is needed on
fungus-based insecticides to better understand how they may be
used in a turfgrass pest management program.
are microscopic roundworms that attack and kill insect
caterpillars and grubs, and they continue their life cycle by
reproducing within the dead host. These types of nematodes are
beneficial organisms that naturally occur in most soils and are
not considered a threat to plants and wildlife other than insects.
They pose no threat of contamination to streams, lakes or
groundwater. Entomopathogenic nematodes are mass-produced and
marketed by only a limited number of manufacturers. Unfortunately,
factors such as poor or short shelf-life, sensitivity to heat and
sunlight, and speed of kill have limited the use of nematodes.
These factors, compounded by the decision of some companies to
discontinue marketing nematodes, have reduced nematode
Spinosad is in a
relatively new class of insecticides called naturalytes that
contain two fermentation-derived substances produced by the
bacterium Saccharopolyspora spinosa. This bacterium is a
naturally occurring microorganism that acts as both a contact and
a stomach poison, but is more effective if eaten by the insect
pest. Spinosad is similar to conventional synthetic pyrethroids in
that it is effective at very low use rates and has a fairly short
residual activity. Spinosad, however, affects the insect nervous
system by causing tremors, rapid paralysis and death. Because of
the aforementioned characteristics and its low toxicity to humans
and wildlife, spinosad may become an important resource for
Biorational pesticides will
become important resources for turfgrass managers and their
pest-management programs. Demand will likely grow for these new
tools as the EPA implements restrictions on pesticide uses,
registration and labeling, and as chemical manufacturers
voluntarily remove or decline to produce chemicals for turf to
preserve more lucrative markets.
1. Brandenburg, R.L. 1999.
Food Quality Protection Act may limit pesticide choices. Golf
Course Management 67(2):58-61.
2. Guillebeau, P. 1998. Food
Protection may limit pesticide use. Golf Course Management
3. Potter, D.A. 1998. Destructive
turfgrass insects: biology, diagnosis, and control. Ann Arbor
Press, Chelsea, Mich.
4. Ware, G.W. 1989. The pesticide
book, 3rd edition. Thomas Publications, Fresno, Calif.
R. Chris Williamson, Ph.D., is
a turfgrass and ornamental entomologist at the University of