Apterae of the green peach aphid, Myzus persicae, on detached cabbage leaves were exposed to a Pandora delphacis conidialshower (112 conidia/mm2) and were then observed for reproduction and mycosis development at different temperatures (10-30 C)and relative humidities (74-100% RH). Based on daily counts of nymphs and adults (living and mycosed) at each regime, the fecundityof apterae exposed to P. delphacis was greatly reduced with the net reproductive rate (R0) and the innate capacity for increase(rm) declining at all temperature and humidity regimes compared to those of unexposed aphids. Moreover, the rm estimatesfor batches of exposed aphids were significantly different among the temperature regimes, being parabolically related to temperature,with the largest rm being obtained at 20-25 C. However, there was no significant effect of RH on rm. During a 30-day period ofobservation, the development of P. delphacis mycosis greatly suppressed the increase of aphid populations relative to the control andthe fungus played a more important role in the control of aphids at the regimes of 20-30 C and P95% RH than at the others. Thecumulative mortality caused by P. delphacis was P80% at all humidity regimes at 30 C and at 74%, 95%, and 100% RH at 25 C.However, the mortality was <50% at 10, 15, and 20 C for all humidity regimes, except for 100% RH. The results suggest thatP. delphacis has the potential as a useful fungal agent for control of aphids.

Bioassays of two entomophthoralean fungi, Pandoradelphacis and P. neoaphidis, were conducted on thegreen peach aphid, Myzus persicae. For inoculation,batches of I3-day-old nymphs on detached cabbageleaves were exposed to conidial showers of varyingtime lengths from sporulating fungal mats produced inliquid culture. Eight dosages of each pathogen wereused to inoculate 88-345 nymphs each. The nymphsinoculated were maintained at 18-20℃ and L:D (12:12) at high humidity and were examined daily for mortality.The resulting data were analyzed using a time-dose-mortality modeling technique, yielding the parametersfor time and dose effects of the two fungalspecies. P. delphacis killed the aphid more rapidlythan P. neoaphidis, though both had similar slopes fordose effect. The values of LD50 estimated on days 3-7after exposure decreased from 18.1 to 0.9 conidia/mm2for P. delphacis and from 17.0 to 0.04 conidia/mm2 for P.neoaphidis. The estimates of LT50 for the two pathogenswere similar at dosages of more than 5 conidia/mm2 but differed at lower dosages. Based on the time-dose-mortality relationships fitted and the virulenceindices estimated, P. delphacis is a promising microbialagent for aphid control and is competitive with P.neoaphidis.

Fungal biocontrol agents, including 10 isolates of Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces fumosoroseuswere bioassayed for their lethal effects on the eggs of the carmine spider mite, Tetranychus cinnabarinus. The eggs were naturally laidon detached fava bean leaves on agar in petri dishes at 25 C under a photophase of 12:12 L:D. Suspensions of aerial conidiaproduced on rice were sprayed onto the leaves, yielding three conidial concentrations (No. conidia/mm2) from low to high for eachof the fungal isolates with 3 or 4 replicates (30-65 eggs/leaf or replicate) at each concentration. During a 12-day observation periodafter spray, the infected eggs shrunk in shape, then turned orange-brown for B. bassiana and P. fumosoroseus or dark-gray for M.anisopliae, and eventually had outgrowths of the sprayed fungus when maintained under moist conditions. Egg mortalities caused byfungal infection varied over time but had no change from day 8 or 9 onward. Differences of the mortalities on day 9 were significantamong the fungal species or isolates tested. Based on the LC50 estimates determined by the concentration-mortality relationships ofall isolates from probit analysis, B. bassiana Bb2860 with an LC50 of 548 conidia/mm2 was highly infectious to T. cinnabarinus eggs,followed by P. fumosoroseus Pfr116 (848 conidia/mm2) and Pfr153 (913 conidia/mm2). Two M. anisopliae isolates with LC50s of 1717and 1985 conidia/mm2 were inferior to the three isolates. The other isolates were poor or very poor in ovicidal activity. Our resultsconfirmed the ovicidal activity of the three fungal species and suggested the feasibility to search for more ovicidal isolates fromfungal species that may serve as biocontrol agents against spider mites such as T. cinnabarinus. The mite egg bioassay system developedin this study will be useful towards this goal.

Glutinous broomcorn millets from the crop Panicum miliaceum were first used as substrate to produce granular cultures of Pandoraneoaphidis, an obligate fungal pathogen specific to aphids. Carrying a water content of 36.5% after being steamed in a regular autoclavingprocedure, millet grains of each 15 g (dry weight) in a 100-ml flask were mixed with 3 ml modified Sabouraud dextrose broth containinghalf a mashed colony of P. neoaphidis grown on egg yolk milk agar and then incubated at 20‡C and a light/dark cycle of 12 h/12 h for 21days. Based on individually monitoring conidial production potential of 20 millet grains sampled from an arbitrarily taken flask at 3-dayintervals, the millet cultures incubated for 6^15 days were capable of producing 16.8-23.4U104 conidia per millet grain with conidialejection lasting for up to 6 days. The cultured millet grains individually produced significantly more conidia than apterous adults ofMyzus persicae killed by P. neoaphidis (8.4U104 conidia per cadaver) and sporulated twice longer. The modeling of time^dose^mortalitydata from bioassays on M. persicae apterae exposed to conidial showers from the cultured millet grains and the mycelial mats produced inliquid culture resulted in similar estimates of LC50 (millets: 21.4, 7.3, and 4.9 conidia mm32 on days 5-7 after exposure; mycelial mats:22.1, 10.6, and 7.7 conidia mm32) although the LT50 estimated at a given conidial concentration was slightly smaller for the millet culturesthan for the mycelial mats. This indicates that the millet grains cultured with P. neoaphidis produced conidia as infective as or slightlymore infective to M. persicae than those from the mycelial mats. Based on the sporulation potential, infectivity, and ease and cost of themillet cultures, the method developed in this study highly improved in vitro cultures of P. neoaphidis and may adapt to culturing otherentomophthoralean fungi for microbial control of insect pests.