Two Beneficial Entomopathogenic Nematodes for the control of Crane flies, Tipula paludosa Control
- Crane flies, Tipula paludosa are one of the most important pests of grasses and field crops.
- Crane fly adults look like large mosquitoes with very long legs (Fig. 1).
- Crane fly adults generally emerge from soil during late August/September and they are active throughout October.
- During this period adults mate and their females lay eggs in or on the soil surface near host plants.
- These eggs hatch within 10- 15 into larvae and larvae develop through four developmental stages (instars).
- Larvae are brown in color, legless and because of their thick skin, they are called as “leather-jackets” .
- All the larval stages of crane fly are generally feed on grass roots, crowns and also on above ground plants parts.
- These larvae continue feeding and developing through the winter and the spring.
- Grassy areas that are heavily infested with Crane flies shows typical symptoms of yellowing and dying patches of grass.
Cultural and Biological Control of Crane flies
Properly managed grass can overcome the damage caused by crane flies. For example, cultural practices such as application of right amount of irrigation and fertilization, and reducing thickness of thatch to minimize wet and water logging conditions (these conditions help crane flies to thrive) will help to promote healthy root system, and the movement of water and nutrients in the soil. Thus these practices will help to recover the damaged grass by crane flies.
Two beneficial entomopathogenic nematodes including Steinernema carpocapsae and S. feltiae have been proved to be most effective in infecting and killing young first instar larvae of crane flies.
These nematodes are warm adapted and use ambush strategy to find larvae of crane flies. Since Steinernema carpocapsae nematodes are warm adapted species, they can cause over 80% mortality of first instar larvae of crane flies when temperatures are above 12oC (53.6oF) (Oestergaard et al., 2006).
Steinernema feltiae nematodes:
These nematodes are cold adapted and use intermediate strategy that lie in between ambush and cruise strategies to find larvae of crane flies. Since Steinernema feltiae nematodes are cold adapted species, they can cause over 50% mortality of first instar larvae of crane flies when temperatures are at or below 12oC (53.6oF) (Oestergaard et al., 2006).
Bacillus thuringiensis subsp. israelensis (Bti):
Bacillus thuringiensis subsp. israelensis (Bti) the soil-dwelling gram-negative bacteria generally used as bio-pesticide against many insect pests have also showed a potential to use as effective biological control agent against young larval instars of craneflies.
It has been reported that the Bacillus thuringiensis subsp. israelensis (Bti) is effective in killing over 70% of Crane fly (Tipula paludosa) larvae when they are applied in the fall at temperature as low as 4oC (39.4oF) (Oestergaard et al., 2006).
Since majority of eggs laid by crane flies hatch into young larvae during October (fall season), this is the best month to target young instar larvae with beneficial entomopathogenic nematodes including S. carpocapsae or S. feltiae. It is recommended to apply 23000 nematodes per square foot area (which is equivalent to 1 billion nematodes per acre). For larger area traditional knapsack sprayers or for smaller area water cans can be used for the application of nematodes.
Read following papers for more information on interaction between crane flies, Tipula paludosa and beneficial entomopathogenic nematodes.
- Oestergaard, J., Belau, C., Strauch, O., Ester, A., van Rozen, K. and Ehlers, R-U. 2006. Biological control of Tipula paludosa (Diptera: Nematocera) using entomopathogenic nematodes (Steinernema spp.) and Bacillus thuringiensis subsp. Israelensis. Biological Control 39:525-531.
- Peters, A. and Ehlers, R-U. 1994. Susceptibility of Leatherjackets (Tipula paludosa and Tipula oleracea; Tipulidae; Nematocera) to the Entomopathogenic Nematode Steinernema feltiae. Journal of Invertebrate Pathology 63: 163-171.