The clover stem borer, Languria mozardi Latreille (Coleoptera: Languriidae), is a widespread, native North American beetle (Wildermuth & Gates 1920; Vaurie 1948). The adult feeds primarily on pollen and foliage of its host plant but has been observed feeding on corn silks (Zea mays L.) and wheat heads (Triticum sp. L.) (Wildermuth & Gates 1920). Larvae tunnel inside the stem of host plants, feeding on the pith and softer inner portions of stem. Stem tunnels can be 75 cm in alfalfa, Medicago sativa L. (Wildermuth & Gates 1920). Economic injury to forage crops can result from the tunneling activity of larvae (Wildermuth & Gates 1920) but Folsom (1909) viewed L. mozardi as being of secondary importance, if at all, in clover.
Languria mozardi is univoltine in the Eastern United States and trivoltine in the South-western United States (Wildermuth & Gates 1920). Overwintering is typically as adults under leaf litter and debris, but overwintering of larvae in stems has been reported (Wildermuth & Gates 1920). Larvae mature within the host stem; pupate in the stem, and adults eclose and spend the first 2– 3 d of adult life within the stem (Wildermuth & Gates 1920).
SPECIMEN DATA FOR LANGURIA MOZARDI IN SOYBEAN STEMS.
Languria mozardi has a wide host range including plants in the families: Asteraceae, Brassicaceae, Campanulaceae, Fabaceae, Malvaceae, Poaceae, and Urticaceae (Folsom 1909; Wildermuth & Gates 1920; Vaurie 1948; Ward et al. 2007). Vaurie (1948) reported a dead adult in the erect stem of a soybean in South Carolina in Nov (no year or date mentioned), but did not list soybean as a larval host plant. Below we present documentation of L. mozardi utilizing soybean, Glycine max (L.) Merr. as a host plant.
During soybean stem dissection to detect Dectes texanus LeConte in Tennessee, Missouri, and Arkansas, we found L. mozardi within stems (Table 1). The larva and pupae were reared to adulthood and adults are housed as specimens in the University of Missouri Delta Research Center collection with the exception of record 1 which was documented photographically (Fig. 1). Vaurie (1948) was used to key all adult specimens to L. mozardi.
Eggs of L. mozardi were not discovered in soybean stems; but it can be assumed that soybean is a larval host based on the biology of stem boring insects and the presence of 1 larva, and pupae and adults in soybean stems. Exit holes smaller than associated with D. texanus have occasionally been found associated with non-occupied but tunneled soybean stems and may represent L. mozardi successfully growing from egg to adult within soybean.
Dectes texanus was the only insect commonly recognized as stem boring in soybean stems in the mid-south. Genung & Green (1965) reported 4 soybean stem boring insects in the Florida everglades, one of which was Languria sp. (possibly L. marginipennis (Sz.)) boring in leaf petioles with a mention that a related species (presumably L. mozardi) is a pest of other legumes. The presence of this second stem-boring species within midsouth soybeans mandates careful identification of beetle larvae encountered to assign stem damage to the proper insect.
As a result, tunneled, but unoccupied, soybean stems in the midsouthern United States can not be assumed to be from D. texanus tunneling. Dectes texanus is a large, univoltine insect that overwinters as a larva within the soybean stem (Hatchett et al. 1975). Languria mozardi is a smaller, possibly multivoltine insect that typically overwinters as an adult outside of the soybean stem (Wildermuth & Gates 1920). These differences in biology lead to differences in how stems are tunneled. Sample size is small, but it appears that L. mozardi tunnels are less extensive with finer frass than those of D. texanus. Additionally, D. texanus makes an overwintering chamber 5–7 cm above the soil surface in the soybean stem (Hatchett 1975) with a frass plug positioned below a girdled spot where the stem will potentially lodge; L. mozardi does not do this. Post-harvest sampling of soybean stubble will likely only reveal D. texanus larvae and/or overwintering chambers as demonstrated by the 479 larvae from post-harvest soybeans reared to adulthood by Tindall et al. (2009).
Based on limited observations and known biology, it is anticipated that soybean stem surveys earlier in the season could detect greater numbers of L. mozardi. Expanding the geographical range of soybeans as a larval host of L. mozardi is also likely if the search area is expanded, because both L. mozardi and soybeans are widely distributed within North America. It is not known if soybeans are utilized by 1 or 3 generations of L. mozardi and if stem tunneling is more common in younger or older plants. At this time, the authors do not think L. mozardi has an economic impact on soybean production. Languria mozardi has a wide host range and preference among hosts is not known. It is unknown if there are any interactions between D. texanus and L. mozardi. Future work is needed to explore these questions.
Languria mozardi larva, pupae and adults were recovered from soybean stems during stem dissections to detect Dectes texanus in Arkansas, Missouri, and Tennessee demonstrating that soybean is an acceptable host plant. This is the second native stem boring insect to adopt the introduced soybean as a larval host in the mid-southern United States.