Rick L. Brandenburg & C.B. Williams III
CAUTION This information was developed for North Carolina and may not apply to other areas.
Over the past
several years mole crickets have become the number one insect pest of home lawns,
golf courses, municipal and commercial properties, and sod farms along the North
Carolina coast. Two species are present as pests along the southeastern coast,
the tawny mole cricket (Scapteriscus vicinus) and the southern mole cricket
(S. borellii). The tawny is the most destructive species of mole cricket
since it feeds almost exclusively on the roots and shoots of grass. Southern
mole crickets may feed a little on the roots, but are primarily predators feeding
on small creatures that live in the soil. Both species do considerable tunneling.
A third species, the northern mole cricket (Neocurtilla hexadactyla)
occurs throughout the state but is less damaging. The tawny mole cricket has
been a pest in North Carolina only since 1987 but has become the most damaging
species. This pest remains a challenge to effective management. Mole cricket
management requires a full-scale program for best results. This publication
recommends the most economical and effective mole cricket management plan.
Mole crickets require advanced planning and appropriate preinfestation management strategies, unlike other insects that can be effectively controlled once a threatening population is observed. If serious damage is allowed to occur before control is begun, the battle has already been lost for that particular year.
An understanding of the life cycle of mole crickets is critical to managing this pest. In general, the life cycles of the different species are similar. For control purposes, the life cycle of the tawny mole cricket will be discussed. There is only one generation per year. Mole crickets have three basic developmental stages: the egg, the nymph or immature, and the adult.
Overwintering takes place as either large nymphs or adults that can remain
somewhat active throughout the winter. Winter damage is seen as short tunnel
mounds. As the soil temperature rises in March and April, the crickets do more
tunneling. Crickets that overwintered as nymphs finish their development into
adults during the spring. In late March and early April, the adults begin to
fly and mate. The adult males locate preferred sites to lay eggs and dig a small
tunnel with an opening exposed to the surface. This is one reason why mole crickets
seem to appear in the same location each year. This chamber is funnel-shaped
and acts much like a megaphone for the males when they begin their calling.
The male produces a soft toad like call for about an hour after sunset. This
can often be heard on warm evenings in April. The call attracts the females
Shortly after mating, egg laying occurs (end of April or early May). Mated females dig down 3 to 10 inches in the soil and lay a cluster of about 35 eggs in a small chamber. Females usually construct three to five chambers and lay a total of 100 to 150 eggs. The round, translucent and white eggs hatch between late May and July. Egg hatch requires about 20 days if the soil temperature is warm or a little longer under cooler soil conditions. The southern mole cricket may continue to lay eggs throughout the summer and hatch can occur in August and September. The males die after mating and the females die shortly after completing egg laying.
The newly-hatched immatures or nymphs are small, usually about a 1/4 inch in
length. As they grow, the nymph stage goes through six to eight molts similar
to a snake shedding its skin. Small nymphs have no wings, but the larger nymphs
have small wing pads. They continue to feed and grow through the summer. These
insects are most destructive in late August through early October. Individual
tunnels may exceed 10 feet in length. Mole cricket activity is regulated by
temperature and soil moisture in ways that are not well understood. However,
most feeding does occur at night, especially after rain or irrigation. During
July and early August, the grass is often growing aggressively and the nymphs
are too small to produce noticeable damage.
By October, the nymphs reach the adult stage. However, a few will overwinter as nymphs and develop
into adults during the winter and spring. Activity is quite sporadic at this time of year. During cold weather, the crickets may stay deep in the soil. However, prior to the cold front, active tunneling near the surface may increase for a short time.
General Control Procedures
The extent to which mole crickets need to be controlled is based on the turf use and your tolerance to damage. Therefore, it is appropriate to divide the turf into four distinct groups: golf courses, home lawns, recreational areas, and sod farms. The initial stages of developing a management plan for mole crickets will be the same regardless of the setting. However, specific control measures will differ with management objectives.
First, it is critical to determine those areas most at risk. Developing a good
appreciation of exactly where the mole cricket populations are most abundant
is step one. When past damage has been serious, this is often quite easy. The
best approach is to use a concept referred to as "mapping." This approach
is basically a visual record of mole cricket activity and abundance over the
turf area. This record can be kept on a property blueprint, survey map, or a
drawing kept on the wall of a maintenance shed. It needs to be reasonably accurate,
permanent, and readily accessible. The more frequently and accurately the map
is updated, the more valuable it will be to the user. Few turf areas require
treatment over the entire area. At the same time, little evidence of mole crickets
is obvious when it's the most effective time for treatment. Good mapping will
help solve both of these problems.
If you start in the winter, note those areas where you see mole cricket damage,
the loosened soil and tunnels at the surface. Make note if these are southern
exposures with slightly higher soil temperatures that may increase cricket activity.
More tunneling could be a reflection of soil temperature and not cricket abundance.
As the temperatures warm in the spring and activity increases, record those
areas that seem to be the worse. If damage becomes apparent, then treatment
may be required. Spring treatment is not recommended, but some population reduction
is possible. Unless the area is very isolated, spring treatments will have only
a slight impact on reducing the number of adults that come into the area to
lay eggs. Damage is usually minimal after the middle of May. After egg laying
is finished, the damage from the adults rapidly diminishes. Since the majority
of the nymphs hatch in June and July, there will usually not be any visible
mole cricket damage. This is the time when a soapy water flush is an effective
tool to monitor cricket egg hatch and abundance in the turf. Mix two tablespoons
of liquid dishwashing detergent in two gallons of water (preferably in a sprinkling
can) (lemon-scented detergent seems to work best). Use the soapy water mixture
to soak an area of approximately one square yard. After applying the solution,
carefully observe the area for movement. Small nymphs are difficult to see as
they emerge from the soil. Many times the crickets will come out of the soil
quite rapidly, but will stop moving upon reaching the surface. As soil temperatures
drop in the fall and crickets grow, the soap drench becomes less effective and
decreases in effectiveness into the spring.
If the soil is very dry, a second drench of pure water may be necessary to
flush the crickets. In very wet soils, the drench may be less effective because
the soap does not penetrate the soil. Do not use a more concentrated detergent
solution as some phytotoxicity to the turfgrass may occur.
By beginning soap flushes weekly in June and comparing average number of crickets each week, one can develop an understanding of the egg hatch for that year. The number of nymphs usually increases rapidly through June but by late June, the numbers normally increase more slowly. Flush counts as high as 25 small nymphs per square foot have been recorded in North Carolina the last week of June. When mole crickets approach 1/2 inch, it is time to begin the main summer treatment. Treating after most of the eggs have hatched but before the earliest hatching crickets are longer than 1/2 inch, three goals are accomplished.
First, the crickets are not treated until the majority of the eggs have hatched
and this provides control for most of the crickets. Second, the insecticide
residual activity will kill many of the remaining crickets yet to hatch. Finally,
timely application provides control prior to the appearance of any noticeable
turf damage. In nearly all situations, treatment in midsummer is the most effective
time to apply insecticide. The crickets are small and susceptible to insecticides
and the soil temperature is warm and conducive to good pesticide efficacy. Historically,
turf was often not treated at this time because the mole crickets went unnoticed
and damage became severe in August and September. The optimal time for the midsummer
treatment will usually be from about June 24 to July 10 in North Carolina, except
if the soil is very dry. During the summers of 1992 and 1993, we had very dry
conditions in many areas infested with mole crickets. This dry weather forces
the crickets deep in the soil. Irrigation cannot make up for what nature leaves
out. When it is extremely dry, it is best to wait until significant rains restore
soil moisture. Even though the mole crickets will grow larger, they are generally
down quite deep in the soil. Treatments applied during very dry conditions are
not going to be very effective since the mole crickets are so deep. This is
a judgment call on the part of the turf manager, but our experience leads us
to believe everyone should consider this point.
No one treatment will be 100% effective. Our trials have shown great variability
in how well a treatment works from one location to another and from one year
to another. Mole cricket behavior is influenced by its surroundings and weather,
soil moisture, and other factors that change constantly. These factors influence
the actions of the mole cricket and the effectiveness of the insecticide. Rarely
do we see the same treatment response twice in a row. Consequently, treated
areas may need retreatment in August and September, especially if initial populations
were very high. Each subsequent treatment will be somewhat less effective as
the crickets are larger. Additional treatments may sometimes be needed in October
or November in heavily-infested areas. Treatments applied in December, January,
or February provide variable, but generally poor, control since the mole crickets
activity widely fluctuates with the weather. Make sure the soil is moist prior
to application of any insecticide treatment. All treatments except baits and
acephate (Orthene) should be watered in with 1/4 to 1/2 inch of water. It is
important to follow these guidelines closely. Do not overwater as to cause runoff
or puddling. Apply treatments late in the day, since the crickets are active
that evening. Acephate (Orthene) is particularly susceptible to sunlight and
should never be applied in the morning or afternoon during the summer months. Acephate is no longer labeled for home lawns.
Baits have proven somewhat effective against adults in the fall and spring.
They should be applied to moist but not soggy soil but should not be watered
in. Any water, either irrigation or rainfall, immediately after the application
of a bait diminishes its effectiveness. The safe use of pesticides should always
be the prime concern. Some insecticides call for watering in after treatment
to ensure safety to man and animals as much as to provide product effectiveness.
Follow all reentry restrictions and label directions.
Nonchemical Control Strategies
There is great interest and demand to develop nonchemical control technology for mole crickets in turfgrass. Great advances have been made in nonchemical control in the past few years; however, few approaches provide acceptable control at this time. The future does hold promise for new innovations. Studies have shown that the coarser textured bermudagrass cultivars are less susceptible to mole crickets than the finer textured hybrids. This knowledge may be used in turf areas where fine texture is not important. There has been considerable work on biological control of mole cricket in North Carolina. A parasitic fly has been released and studies are underway to determine its ability to establish here. In addition, work is still underway evaluating a parasitic nematode that attacks the mole cricket. Nematode sprays can be applied with conventional application technology. This nematode has shown good potential.
Specific Treatment Approaches
Mole cricket damage in home lawns is relatively new in North Carolina. The best philosophy is to target a single pesticide treatment to the areas of highest infestation during the first week of July. Mapping again plays an important role in determining which areas to treat. Most home lawns do not require total elimination of the crickets. Therefore, whole lawns usually don't need treatment and the treated areas may not need to be retreated even if some crickets survive. However, if damage becomes evident in late August or early September, regardless of whether the area was already treated, then spot treatments are recommended. The higher the level of management of the lawn, the less damage that can be tolerated. For example, a close-cut hybrid bermudagrass will require more attention than a Bahiagrass lawn. At the same time, a healthy lawn can tolerate more feeding and has the ability to cover damage better than a poorly maintained lawn.
This same philosophy would hold true for commercial properties. Generally the
level of expectation will be slightly lower, and some mole crickets can be tolerated
in all but the most visible and highly managed areas. Mapping can significantly
reduce the total amount of area that requires treatment. In addition, mapping
will ensure that "hot spots" are treated and no unwelcome surprises
with large bare spots occurring from previously undetected mole cricket outbreaks.
It is understandable to get caught once by surprise, but once you begin mapping
and understand where the mole crickets prefer to stay, there's no excuse for
severe damage to recur in such a location.
Chemical Recommendations for Home Lawns -
Recommendations for insecticides approved for control of these insects in home lawns can be found under "Mole Crickets" in the Insect Control in the Home Lawns section of the NC Agricultural Chemicals Manual. Follow all label directions.
Commercial Sites -
Controlling mole crickets on sod farms is no different from any other turf setting. Making economically sound decisions on the need to treat can be difficult. Obviously, the sod needs to be relatively free from stress so as to maintain quality. Additionally, healthy turf is essential for customer satisfaction after the sod is laid. If serious infestations have been a problem in certain areas of the sod field, then those areas should be treated with the midsummer treatment. Sod should be checked prior to harvest to detect damaging populations. Moderate to severely infested sod will be difficult to transplant at any time of year. A few mole crickets in a sod field will exist no matter how effective the treatment schedule. Reducing mole cricket populations to tolerable levels is a reasonable goal. However, attempting to eradicate them is not only extremely expensive and environmentally foolish, but virtually impossible.
Shipping sod to the north and west of the mole cricket infested area may cause
alarm on the part of the buyer if even a little mole cricket damage develops
following sod laying. The likelihood of expanding the range of the mole cricket
or creating a localized problem is fairly low since the survival of the cricket
is dependent upon weather and soil type which will be less favorable farther
inland. Sod farms have special environmental significance. Insect pest control
can create special problems. These large areas of turf are often temporary homes
for migratory bird species. This is one reason why the use of diazinon was banned
from sod farms as well as golf courses a few years ago.
Three major concerns face the managers of recreational areas battling mole crickets. First, the turf must have a good root system to withstand the stress of recreational play. Also, the appearance of some recreational areas is of prime importance and aesthetics must be maintained. Finally, the optimal time to treat is often a time when athletic areas are the busiest. All three concerns affect mole cricket management. Poor treatment timing can have serious economic, environmental and cultural impacts.
A good turf management program must be maintained to provide the desired type
of recreational playing surface. The late June -early July treatment is the
most effective, and thus should be an integral part of the overall management
program. But as previously mentioned, the midsummer application often directly
conflicts with the time of busiest use of these recreational areas. Pesticide
application for control of mole crickets may require the area to be closed for
a day. For this reason, some managers may hesitate to treat. Remember, if the
treatment is not applied at this time to areas infested with crickets, the resulting
damage may require additional pesticide applications to prevent serious turf
damage. As with other settings, the plan of mapping, timely summer treatments,
and follow-up spot treatments remains the best approach. Safety to the users
of the area, however, is no different than safety to the occupants and users
of home lawns and the workers and handlers in sod production.
Golf courses are managed the most intensely of all turfgrass areas and also require some special considerations. They differ among themselves in their management programs and budgets. In addition, turf management requirements will vary significantly on the tees, greens and fairways. These differences require different programs.
Each golf course has certain areas that require special considerations. Are there infested areas directly adjacent to water? Is fairway maintenance less important than the tee and green maintenance? How much play and environmental stress does the turf experience? These and other questions will play a vital role in how mole crickets are managed. To begin a control program we again return to the concept of mapping. This is a crucial step since many courses will have over 100 acres of turf to monitor. The best plan we have is a blueprint of the courses tacked up on the maintenance shed wall with areas of infestations marked in colored pencil. Once the spring mapping is conducted, those areas of heaviest infestation are marked in red. Other questionable areas with milder infestations can be marked with another color. Marked areas are then examined throughout the month of June using soap flushes. If the flushes confirm serious infestations and soil moisture is adequate, a treatment can then be applied. Other areas with lesser infestations in the spring can also be tested with the soap flush and treated if numerous crickets come to the surface.
There is no established threshold to determine the need to treat. Our suggestion
is to treat any areas that have 6 or more mole crickets per square yard surface
in a fairway. Tees and greens might be treated if any mole crickets can be flushed.
If large numbers of mole crickets are observed in the marked areas of the cricket
map, then it would be wise to use the soap flush in other areas. While soap
flushing may appear time consuming, accurately identifying those areas that
need treatment certainly makes the time spent worthwhile. After all midsummer
treatments are complete, the course should be examined closely every week beginning
August 1 for signs of damage. If damage becomes apparent, retreatment should
be immediate. Damage should never be allowed to exceed more than three areas
of tunneling per square yard. ALL of the golf course needs to be checked each
week since some areas probably did not receive the midsummer treatment. Mole
crickets can disperse long distances and though they prefer to lay eggs in the
same areas, they occasionally spread to new sites.
NEVER treat areas immediately adjacent to water. If mole crickets are a serious
problem there, a natural area or ornamental planting other than turfgrass may
be desirable. The use of parasitic nematodes may be a good alternative. Use
extreme caution near water. Do not use highly water-soluble products on any
slope or near any water. Baits can effectively be used in areas such as the
rough where no irrigation is available to water in other products. The baits
are best applied in the evening after a rain but not just before irrigation
or a rain is expected.
Chemical Recommendations for Commercial Sites -
Recommendations for insecticides approved for the control of mole crickets on sod farms, recreational areas, golf courses and other commercial sites can be found in the Commercial Turf Insect Control section of the NC Agricultural Chemicals Manual. Please note the formulation, application, and site restrictions for some products. Follow all label directions. Several new products have become available within recent years.
Subsurface Application Technology
In response to the demand for effective mole cricket control in the most cost-effective and environmentally-sound approach, new equipment is being developed. The main objective of this equipment is to apply the pesticide below the soil surface. This method results in improved effectiveness and reduced surface residue.
Two types of equipment are available, one for applying liquid material and
the other for applying granular formulations. Both have some advantages and
disadvantages. Rather than provide specific information on equipment, the following
paragraphs discuss items the turfgrass manager should consider before purchasing
or contracting for such equipment. There is insufficient data to support the
claim this equipment ALWAYS provides better control. There is even less evidence
that insecticide rates can be reduced. Some studies have shown both of these
statements may be true, but we have yet to prove it occurs consistently. Preliminary
research indicates control is at least as good if not slightly better through
subsurface application. The reduction of rates is more questionable. Our data
have shown that some rate reductions may be possible, but certainly not a 50%
reduction that some companies are claiming.
The other issue is the environmental safety issue. The application of liquid
sprays through a high-pressure liquid injector probably reduces surface residue
when followed by an irrigation. The amount of granules that are actually placed
into the soil by the granular slit applicators is less clear. Some observations
with early models indicate that only a small percentage of granules are actually
placed in the soil and the rest get scattered around. In general, this equipment
is more expensive and slower than conventional application equipment.
Many of these studies were done with models that are now being improved dramatically
and may provide better in-soil application. None of this equipment diminishes
the need to follow applications with irrigation. Nor does this equipment allow
one to skip the reentry restrictions on the label. At least two products now
have guidelines for subsurface application on their label. In our opinion and
experience, subsurface equipment may be a step in the right direction. More
work needs to be done on each specific pesticide as to the best application
technique and rate. Equipment is also being improved as interest in these products
increases. Our best advice is to study, observe, question, and read on the subject
before making any investment in subsurface application equipment whether it
be for lease, purchase, or hiring a custom applicator.
We have conducted trials using adjuvants during 1992 and 1993 and not seen any significant improvement in insecticide performance. Our studies have focused on the use of adjuvants with late afternoon applications of acephate (Orthene). While more crickets may be found dead on the surface the next morning, we have not observed any reduction in damage over the next two weeks. That leads us to believe that the adjuvants simply make more of the crickets die on the surface.
Mole crickets are pests that require a year round management program. Unlike pests such as cutworms, that can be easily controlled after they appear, mole cricket controls should be managed in an aggressive manner that includes scouting, flushing, mapping, and the timely application of pesticides. Studies in North Carolina have documented that even areas under serious attack can be restored within a couple of years through a good management program. Do not expect to completely correct years of neglect in a single summer. Mole crickets can be managed now, but new products and equipment promise to make the job easier in the future.
WUNC-TV Almanac Gardener Video on Mole Crickets (requires Real Player)
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Because environmental conditions, methods of application by growers, and performance of the chemicals may vary widely, control results may also vary.
Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical.
Published by North Carolina Cooperative Extension ServiceDistributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Rick L. Brandenburg & C.B. Williams III, Extension Specialists
ENT/ort-79 December 1993 (Last revised May 2002)
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