Relationship Among Orangestriped Oakworm (Lepidoptera: Saturniidae) Frass Length, Frass Production, Host Plant, and Defoliation

Defoliation of urban oak trees by the orangestriped oakworm, Anisota senatoria (J. E. Smith), and associated frass has become a significant problem in southeastern Virginia. Measurements of frass length and production provided a decision-making guideline for A. senatoria management. Frass length was used to differentiate A. senatoria instars reared on Q. palustris (Muenchhausen), pin oak. Host plants significantly affected A. senatoria frass length and production per larva and host plants should be considered when determining instars. Frass length was longer and frass production higher when larvae were reared on Q. nigra (water oak), Q. phellos (willow oak), Q. coccinea (scarlet oak), and Q. palustris compared with six other species. Frass length was shorter in second, fourth, and fifth instars when larvae were reared on Q. alba (white oak) compared with six, eight, and five other species, respectively. Landscape fabrics were used to collect frass and recovered 90% of all frass deposited. Frass production on small pin oaks (mean ht = 2.1 m, mean diameter at breast ht = 6.3 cm) was significantly correlated with defoliation. An aesthetic injury level of 25% defoliation resulted in frass collections of 2.2 g per tree.