Biological Control of Pest Mole Crickets in
Florida – to Benefit Ranchers
J.H. Frank, for the University of Florida/IFAS
Mole Cricket Research Program

The largest cattle ranch in the USA is in
Florida.
Florida has about 7.6 million acres in cattle range.
In 2006, Florida ranked 12th nationally in beef cattle with approximately 926,000 head. In 2005, 880,000 calves were born in the state.
The worst insect pests of pasture grasses are (were) invasive mole crickets of the genus Scapteriscus .

most widespread
Scapteriscus borellii , S. vicinus , S. abbreviatus all arrived from southern/ eastern
South America in
1899-1924 in ship ballast.
the major pest flightless, so a minor pest

They destroy vegetable plantings, golf courses, lawns, playing fields, and pastures throughout Florida (and other southern states).

After the cheap, effective, persistent chemical chlordane was banned in the 1970s...
The Florida Cattlemen’s association (FCA) asked the Florida Legislature for help…
The Legislature instructed the Agricultural
Experiment Station to begin a research program on mole crickets…
… which fell upon the Entomology &
Nematology Department to perform

Larra bicolor attacking a mole cricket. This crabronid wasp is widely distributed in South
America and is now spreading in northern
Florida.
from Bolivia in 1988-1989
Its larvae are koinobiont ectoparasitoids.

Bolivian stock, released in 1988, its known distribution by end of 2008
Larra bicolor
Brazilian stock, introduced from
Puerto Rico in 1981, its known distribution by end of 2008

Adult L. bicolor need nectar sources. The best source detected is
Spermacoce verticillata
(Rubiaceae) from the
West Indies. Wasp populations may be enhanced by planting this ‘weed’/ ‘wildflower’

A preliminary estimate is of almost 70% generational mortality inflicted on pest mole crickets where this wasp is wellestablished. Effects are now being calculated/modelled more precisely.
It may be able to achieve >70% mortality where its population is managed by provision of nectar sources (like butterfly gardening).
Adult wasps can be monitored visually at nectar source patches.

Juvenile Steinernema scapterisci nematodes emerging from a dead mole cricket. This species was imported from
Uruguay in 1985 as a classical biocontrol agent.
But it is achieving more use as a biopesticide because the concept of a pesticide is familiar to users.

Steinernema scapterisci confirmed establishment by application of < 2 billion in 1989-1990 by release of a few millions in 1989-1990
Applications were made in more counties in 19992002 by the “Mole
Cricket Task Force” and by sales – results are yet unevaluated.

Eight years after application of S. scapterisci in pastures in three counties, few mole crickets were trapped during 8 months of
1997, but infection levels were still high.
County Number of mole crickets trapped
Flagler 60
Osceola
Pasco
18
42
% infection
37
50
40
Observed % infection underestimates generational mortality because of the brief development time of the nematode vs the single annual mole cricket generation.

Twelve years after application of S. scapterisci on golf courses, few mole crickets could be trapped in October 2001, but infection levels were still moderate
Golf course
Ironwood GC
Gainesville G&CC
Number of mole crickets trapped
59
91
% infection
17
14
Observed % infection underestimates generational mortality because of the brief development time of the nematode vs the single annual mole cricket generation.
Steinernema scapterisci serves as a successful classical biocontrol agent, not just a biopesticide.

from
23 o S in
Brazil in 1988 its larvae are koinobiont endoparasitoids copyright R. Noonan

30 o N
Ormia depleta from releases in 1988-1992 counties occupied all year counties occupied mainly in the autumn of each year
Presence of O. depleta in all counties indicated yellow or orange-brown has been affirmed by trapping specimens.
29 o N
28 o N

Ormia depleta adults, just like Larra bicolor , may need nectar sources. An analysis of gut contents of wild-trapped flies showed they use melezitose, from insect honeydew, as a source.
But insect honeydew is not their only nectar source. Research has not progressed to the point where we know what works best, much less how to manipulate it.
Funding for such research has been hard to obtain – is “too basic” for many agencies, is
‘too applied” for another.

a sound-synthesizer producing male song here is the bait to trap mole crickets phonotactic flies are trapped here timer
S. vicinus mole crickets are trapped in this bucket of sand
S. borellii mole crickets are trapped here

200
150
Gainesville
Gainesville baseline period baseline=
100
100
50
0
250
S. vicinus
Gainesville
200 S. vicinus
Gainesville
150 baseline=
100
100
50
0 baseline period
Tens of thousands of period trapped annually in
1979-1988. For simplicity, data were converted to a baseline figure of 100 (the average annual catch for those years).
biocontrol period
There is no trend, upward or downward, for those years. The question was – what will happen when biocontrol agents arrive at the trap sites?

200
150
Gainesville
Gainesville baseline period baseline=
100
100
50
0
250
S. vicinus
Gainesville
200 S. vicinus
Gainesville
150 baseline=
100
100
50
0 baseline period biocontrol period
4% of baseline biocontrol period
<0.5% of baseline

So by 2000, winged mole crickets no longer swarmed around neon and sodium lights (at gas stations and parking lots) in the early spring, at least in Alachua County and neighboring areas.
A large lawn care company reported for
Gainesville that its accounts had dropped from about 60 to 3 or 4 (those lawns that it treated with chemicals to control mole crickets).
The state funds that had been “earmarked for mole cricket research” in 1979 “lost that earmarking” in 1991  , by which time, however, 3 biocontrol agents had been introduced and established.

But the nematode Steinernema scapterisci was became unavailable commercially in 1996.
Norm Leppla (Florida IPM co-ordinator) worked with the UF Office of Technology Licensing to negotiate a license agreement in 2000 with an experienced company. The nematode was again brought to market as Nematac S

.

So everything was fine and the biocontrol agents were spreading? And there was a website on mole crickets plus online extension publications about the biocontrol agents
But the research committee of FCA again listed mole cricket research as a major objective.
The disconnect seemed to be because:
● no training sessions for Livestock Extension
Agents had been held – so they were not promoting use of biocontrol.
● machines for applying the nematode seemed unavailable for rent.

So we consulted our longest-standing Livestock
Extension Agent and the FCA, and they supported the concept. We applied to SRIPM.
We were funded for calendar year 2010. And then additional Livestock Extension Agents became enthused and carried a lot of the load!
I asked Livestock Extension Agents everywhere to identify sites with lots of mole crickets, and I visited those sites. Somewhat to my surprise, all with promising sites proved to be in northeastern Florida.

We are immensely grateful to the Southern
IPM Center for most of the funding that made this project possible.
An assurance
The native, non-pest mole cricket Neocurtilla hexadactyla is only distantly related (belongs to another tribe or subfamily). Natural enemies of Scapteriscus mole crickets, imported from
South America, do not affect N. hexadactyla.
There are no “non-target effects.”