A Native Crane Fly Species may Be a Potential Pest in Alfalfa Fields of Kentucky

Adult crane flies (Diptera: Tipulidae) are often misidentified as giant mosquitoes, they are actually different in size (0.8 to > 1 in. of body length) and belong to a different family. The larvae of crane flies are known as “leatherjackets” and in this case the larvae are found around 1-2 inches depth in the soil (Figure 1B), displaying tan to dark brownish colors, with a retractile head capsule and spiracles.

Most native crane fly species do not represent a threat to agriculture, but they may become pests when certain conditions are met. For instance, some invasive species are considered pests in golf courses and in some pastures. Here is the first report of a native species, Tipula paterifera that was found feeding on roots and foliage of alfalfa in Kentucky (Figure 2). The damage to alfalfa plants can be severe when high numbers of larvae are present in the soil (Figures 2 and 3). This species was previously found feeding on herbaceous plants in grasslands.

The larva of T. paterifera is mostly found within 5-in. depth in the soil and some of them are collected close to the main root of alfalfa plants (Figure 4A). Pupae are found close or on the ground surface (Figure 4B). Between 1 to 10 crane fly larvae/ft2 were found in soil samples in 2022. The larva’s lengths ranged from 0.5 to 0.9 inches. Under laboratory conditions adult females lay on average 397±121 (SEM) eggs, ranging from 41 to 1,361 eggs within 72 h. Eggs are laid on small clusters containing up to 18 eggs. Under dry conditions, larvae remained in hardened soil clumps (Figure 4C). These individuals barely moved unless poked or if the soil clump was intentionally opened. In contrast, larvae in soaked conditions were able to breathe using their annal breathing tubes or spiracles (Figure 4D).

Tipula paterifera larva (as many crane fly species) is physiologically adapted to survive both dry and moist conditions during larval stages. It caused economic damage to alfalfa only when high larvae populations appear (i.e., 2019 and 2021). However, there is no known economic threshold thus far. The outbreaks of T. paterifera in alfalfa fields could be attributed to certain climatic and ecological conditions not yet understood. The low populations of this species detected in 2022 could be explained in part by the extreme drought conditions across the north central U.S. ~ Armando Falcon-Brindis, Raul T. Villanueva and Julian Dupuis