Tipula paludosa

Life cycle

The life cycle of Tipula paludosa, follows a seasonal pattern. The larvae hatch in mid-September and initially remain on the soil surface before moving deeper into the thatch and upper soil layers as they mature. During the winter, they remain underground and as the weather becomes warmer, they feed. The most severe damage occurs in spring when their feeding results in bare patches that are often then overtaken by weeds. Their presence also attracts birds, including crows, which further damage turf as they hunt for larvae. By mid-May, the larvae stop feeding, and enter a nonfeeding stage in June and go just below the soil surface, where they remain throughout the summer. In late August, the larvae pupate, and soon after, the adult crane flies emerge, and mate almost immediately. They then lay eggs in moist soil within 24 hours of emerging, which begins the cycle again. While the adult flies do not feed and have a lifespan of only about two weeks, their larvae are a serious ecological and economical threat to lawns, pastures, and crops.

Invasiveness

Tipula paludosa was introduced to Newfoundland around the 1880s, later identified in 1955 in northern Nova Scotia, and it was reported to cabbage transplants and turnip seedling in Newfoundland. The European crane fly was identified in the western coast of British Columbia in 1965. In 1980 - 1981, there was a major outbreak in Washington state. In 1998, it was identified in Ontario, in 2004 it was detected in New York. The European crane fly was listed as a primary target of the Cooperative Agricultural Pest Survey in 2004 and 2005. The accidental introduction of T. paludosa was the movement of infected soil media.

T. paludosa is considered invasive because of the way it causes damage to lawn, pastures, and hay fields. It does this by feeding on clover and grass species. The European crane fly can also feed on beet, potato, corn and other vegetable crops, ornamental and nursery trees. The most susceptible to invasion are young plants, as they can be chewed at the soil line. Pasture greenland of 10 acres invaded by larva can have an average of 110 larvae per square foot. Means an average of 4.5 million larvae per acre. The lack of effective natural predators and parasites in North America contributes to its invasiveness. Even though there are some birds and insects that eat the larvae, it is not enough to be able to control the population.

Ecological role and economic impact

T. paludosa is a major agricultural pest. It is most known for its larvae that cause damage to lawns, pastures, and hayfields by feeding on the roots, stems, and leaves of grasses and legumes. The larvae feed on all turf and forage grass species, as well as cereal crops. It has been found that they are a serious threat to seedling nurseries, as they damage both bare root and container stock due to chewing the stems at the soil line. In Oregon, the larvae have caused damage to peppermint, grass seed fields, winter wheat, and turnips.

The economic impact of T. paludosa is harsh. Many homeowners treat for crane fly larvae annually, with previous studies showing homeowners in western Washington spending about $12.9 million on treatments. In Northern Ireland, the damage that has occurred to forage grasses was more than £15 million per year. It was found that crop yields increase by approximately 74% when larvae are controlled. The larvae also cause damage as they attract birds like crows, which tear up turf while feeding on them.

Historical outbreaks have shown how large of a problem that the larvae cause. In British Columbia, one farm lost almost 10 acres of pasture grass due to an infestation of approximately 4.5 million larvae per acre. A major outbreak in the Seattle area during 1980-81 caused destruction of lawns, fairways, and golf greens, which helped establish the pest's presence in western Washington.

Mitigation and control

Managing T. paludosa is very difficult as it requires both chemical and biological controls. On lawns, the insecticides that are commonly used are Diazinon and Dursban. In pastures, methyl parathion has been found to be effective. With larval populations naturally declining about 50% between March and May, the best time for treatment is within the month of April. If a lawn has a history of infestations, surveys of the yard, such as digging up small sections of turf and counting larvae, will help to determine whether treatment is necessary. Chemical treatments are recommended if there are more than 25 larvae per square foot within the site.

With Parathion being banned in 2003 in Europe, researchers have looked into alternative control measures, but the results have been mixed. The entomopathogenic nematode, S. feltiae, has demonstrated biological control on the young larvae of T. paludosa. However, it was found that their effectiveness is influenced by temperature and what stage the larvae are in. Another biological control agent, B. thuringiensis, has also been found to be effective against early-stage larvae, however, it requires high application to work. Natural predators, like birds, help to control populations but don't significantly reduce infestations when they occur. Even in areas where birds feed heavily on larvae, studies have shown there was only about a 7% reduction. Other natural enemies, such as nematodes and fungal pathogens, exist but are not present enough to serve as a reliable control method.