Abstract
The lethal humidity (LH50) responses at 20°C of eggs of two strains of Neoseiulus fallacis (Garman) were 71.6 and 69.7%; of three strains of Amblyseius andersoni (Chant) were 62.9, 62.0 and 62.4% and of one strain each of Typhlodromus pyri Scheuten and Metaseiulus occidentalis Nesbitt were 55.0 and 28.4%, respectively. Eggs of three genetically distinct strains of A. andersoni from Oregon, the Netherlands and Italy did not respond differently from one another nor did eggs of freely hybridizing N. fallacis from Michigan and Oregon. Mortality of larvae through development to early protonymphs at 50% RH, 20°C. was 91.9, 82.3, 46.2 and 31.0% for fed mites and 98.1, 83.2, 67.0 and 89.7% for unfed mites of Oregon strains of N. fallacis, A. andersoni, T. pyri and M. occidentalis, repectively. Fed larvae-protonymphs of M. occidentalis and T. pyri were more tolerant of low humidity than fed larvae-protonymphs of N. fallacis and A. andersoni. Mortality was less for fed than unfed larvae-protonymphs of M. occidentalis and T. pyri, but there were no differences for A. andersoni and N. fallacis. Levels of feeding by predator larvae on T. urticae and cannibalism by phytoseiid protonymphs contributed to species differences. Responses to humidity are discussed in relation to geographic and host plant distributions and biological control by single or mixed species populations of phytoseiids.
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Croft, B.A., Messing, R.H., Dunley, J.E. et al. Effects of humidity on eggs and immatures of Neoseiulus fallacis, Amblysieus andersoni, Metaseiulus occidentalis and Typhlodromus pyri (Phytoseiidae): implications for biological control on apple, caneberry, strawberry and hop. Exp Appl Acarol 17, 451–459 (1993). https://doi.org/10.1007/BF00120503
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DOI: https://doi.org/10.1007/BF00120503