Abstract
To study the effects of the pupation depth of western flower thrips (WFT),
Frankliniella occidentalis (Pergande), on the efficacy of entomopathogenic
nematodes (EPN), Heterorhabditis indica strain LN2 and Steinernema
bicornutum were applied at dose rates of 100 and 400 infective juveniles
(IJ) cm–2to WFT that had pupated at different depths. Additionally, the
effects of EPN concentrations and thrips densities were tested on the
pupation depth of WFT. A higher concentration of H. indica was required when
the thrips pupated deeper. Yet applications of S. bicornutum even at a high
concentration resulted in a significantly lower WFT mortality at greater
rather than at shallower depths. Generally, WFT control levels of 5-57% were
obtained depending on depth of pupation, EPN species, and concentrations.
The results clearly indicate that WFT at high EPN concentrations seem to
remain at a certain soil depth in order to avoid EPN attraction by moving
around. Without or at low EPN concentrations, up to 80% of WFT pupated at
the deepest depth of 3-5 cm. However, at higher thrips densities and EPN
concentrations, 45-48% of WFT pupated in the medium depth of 1-3 cm. Thus,
depth of pupation is an important factor in WFT control using EPN.
Morphological and Chemical Factors Related to Western Flower Thrips Resistance in the Ornamental Gladiolus
