Pest mole crickets elsewhere, and their biological control

By mid-2014, 107 valid species of extant mole crickets had been described worldwide. That number will increase as more species are described, especially in Asia. Some of them are rare or even endangered, but a few have become pests. Biological control seems to have been attempted against very few of the pest species, perhaps because biological control requires original research, whereas it is so much easier, although ultimately costlier, to reach for a known but temporary chemical solution. Biological control has achieved 95 percent control of pest mole crickets in northern Florida, with this level of control or even better spreading southward, with the help of an additional biocontrol agent, Ormia depleta. If you want to spend hundreds of dollars per acre for chemical control of pest mole crickets, go ahead — provided that you comply with environmental laws. We present the alternative, low-cost biocontrol solution wherever we can do so.

 

Florida

We have evidence that importation and establishment of classical biological control agents reduced pest mole cricket populations in northern Florida by 95 percent from the 1980s through the years 2000–2004. We believe that this level of control is spreading throughout Florida. The total cost of the 25-year UF/IFAS Mole Cricket Research Program that began in 1979 was about $4.5 million, adjusted to 2013 dollars. It achieved about a 30:1 benefit: cost ratio on Florida ranches alone, not including turfgrass, vegetable culture, or benefits to neighboring states.

 

The southern United States

Two of the invasive pest mole cricket species in Florida have a wider distribution in the southern United States. The southern mole cricket, Neoscapteriscus borellii (Giglio-Tos), and the tawny mole cricket, Neoscapteriscus vicinus (Scudder), have a range extending from the coastal plains of North Carolina southward to Florida, and westward in the coastal plains to eastern Texas. They are acknowledged as pests in all those states. The southern mole cricket has also been reported from Yuma, Arizona (and, arguably, neighboring Imperial County, California); Los Angeles County, California; and in Chihuahua, Mexico.

Beneficial wasps (Larra bicolor) from Florida were released deliberately in the area of Tifton, Georgia, in 2001. They spread from there or directly across the Florida–Georgia border and have now been reported not only from southern and eastern Georgia, but also from coastal areas of North and South Carolina and coastal Alabama and Mississippi. The beneficial fly Ormia depleta has not become established in northern Florida because it cannot withstand cold winters. Small numbers of the beneficial nematode Steinernema scapterisci from Florida were released in the Tifton area by Dr. William Hudson of the University of Georgia, and became established. In 1992, the now-defunct company biosys made experimental applications against pest mole crickets of this same nematode to turf in Alabama, Florida, Georgia, Louisiana, Mississippi, North Carolina, and South Carolina. However, it seems that nobody tested for establishment of the nematode at those sites. In summary, Larra bicolor is established in coastal areas of five states, and there may still be a population of Steinernema scapterisci in southern Georgia, perhaps even elsewhere in the South. Nobody seems to have attempted to measure the long-term effects of these biological control agents on pest mole crickets in southern states outside Florida.

 

The northern United States

The northern mole cricket, Neocurtilla hexadactyla, is a widespread native species in the eastern United States. It exists in Florida, where it has two specialist natural enemies: a wasp, Larra analis, and a nematode, Steinernema neocurtillae. In Florida as in other southern states it rarely if ever is a pest. However, we are aware of recent documentation that it is sometimes a pest of turf in Nebraska. Why should it be a pest in Nebraska when it is rarely if ever a pest in Florida? Could it be that the natural enemies present in Florida are absent in Nebraska? Here is opportunity for original research.

The European mole cricket, Gryllotalpa gryllotalpa, is an invasive species in the northeastern United States, apparently having arrived with potted shrubs from Belgium in about 1913. Occasionally it causes a pest problem in Connecticut, New Jersey, and New York. We are unaware of any attempt to use biological control against it. We have reason to believe that the natural enemies imported into Florida to control Neoscapteriscus mole crickets would be totally ineffective against Gryllotalpa because they belong to separate subfamilies of mole crickets. Gryllotalpa gryllotalpa has been declared an endangered species in the United Kingdom. We do not know whether the natural enemies of Neocurtilla hexadactyla will attack Gryllotalpa gryllotalpa.

 

Puerto Rico and the Virgin Islands

There are only four species of mole crickets in the West Indies. By far the major pest among them is Neoscapteriscus didactylus (Latreille), called in Spanish “changa,” but in English “the West Indian mole cricket.” The latter name is deceptive because the species is native to northern South America and was invasive in the West Indies, albeit long ago. The “changa” is the only important pest mole cricket in Puerto Rico, St. John and St. Thomas, but is absent in St. Croix.

The first specialist biocontrol agent to be introduced and established in Puerto Rico was the beneficial wasp Larra bicolor, from Belem, Brazil, in the late 1930s. An unsuccessful attempt was made to import and establish the beneficial fly Ormia depleta at about the same time. The beneficial nematode Steinernema scapterisci was successfully established in the early 2000s. No attempt has been made to introduce these biocontrol agents into the US Virgin Islands. There still has been no adequate attempt to measure the level of control of pest mole crickets by these biocontrol agents in Puerto Rico. All that reasonably can be said is that pest mole crickets were “devastating pests of agriculture” in the early decades of the 20th century, but are not so now.

 

Other West Indian islands

Neoscapteriscus didactylus (Latreille) is a pest in many islands from Hispaniola south to Trinidad. There has not been an assessment of its control by natural enemies in any of these islands except, in a very limited way, in Puerto Rico. It is not present in Cuba or Jamaica. There is much scope for new research.

 

Hawaii

The invasive pest mole cricket in Hawaii has been called Gryllotalpa africana. However, that name is an error of identification, and the species may be Gryllotalpa orientalis, although that still needs taxonomic verification. A beneficial wasp, Larra polita, was imported from the Philippines and established in Hawaii in 1925. No assessment of its effect has been published. All that can be said is that before 1926 this mole cricket was stated to be an important pest, whereas later there has been scant mention of it as a pest.

 

New South Wales, Australia

The invasive mole cricket species in New South Wales is Neoscapteriscus didactylus (Latreille) the so-called “West Indian mole cricket.” Problems with it could probably be solved by importing the same natural enemies that were imported successfully into Florida — Larra bicolor, Ormia depleta, and Steinernema scapterisci.

 

Southern Africa

A major mole cricket pest species in southern Africa is Gryllotalpa africana. We are unaware of any study on the natural enemies of this species, so we have no suggestions about how biocontrol can be achieved. A solution will require original research, which is the responsibility of local agencies.

 

Asia

Almost all Asian mole crickets are species of Gryllotalpa, and the taxonomy is unsettled. We are unaware of any study of their natural enemies, so we have no suggestions about how biocontrol can be achieved. A solution will require original research, which is the responsibility of local agencies.