Isaria poprawskii sp. nov. (Hypocreales: Cordycipitaceae), a new entomopathogenic fungus from Texas affecting sweet potato whitefly

Isaria poprawskii is described as a new entomopathogenic species similar to Isaria javanica (= Paecilomyces javanicus). It was discovered on the sweet potato whitefly, Bemisia tabaci biotype B in the Lower Rio Grande Valley of Texas (LRGV), USA. Morphological and DNA examinations indicated the distinctness of I. poprawskii from the ex-type isolate of I. javanica. I. poprawskii produced light yellow young colonies to darker yellow with a grayish-violet center to a taupe or a brownish-gray mature conidial mass; conidia hyaline, one-celled, 3.9 (2.9–4.6) μm long × 1.6 (1.4–2.1) μm wide; colored synnemata, but I. javanica ex-type produced white colony, hyaline conidia and no synnemata. A phylogenetic position of I. poprawskii was inferred by a nucleotide sequence analysis of β-tubulin along with standard β-tubulin sequences from GenBank. Fifteen unsequenced isolates, including eight from the LRGV, were investigated. The analysis confirmed that I. poprawskii could be recovered from LRGV fields, and that both I. javanica and I. poprawskii are present in the LRGV in sympatry. I. poprawskii was shown to be closely related to I. javanica; however, it formed its own unique clade, thus confirming its status as a new fungal species. ► Isaria poprawskii is a new fungus species found during epizootics on whitefly at the Lower Rio Grande Valley (LRGV) of Texas. ► It showed colored synnemata and longer conidia than its similar I. javanica. It formed its own phylogenetic clade. ► We found that isolates previously collected from LRGV were misidentified as Paecilomyces, which indeed are either I. poprawskii or I. javanica living in sympatry. ► We also found that isolates from other locations were misidentified as Paecilomyces or Isaria spp.