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To aid the development of compatible biocontrol inocula, a prescreening method for the prediction of compatibility of fungal antagonists was developed. Compatibility between 18 Clonostachys isolates with known antagonistic capabilities against Phytophthora palmivora was tested using intra- or interisolate pairings (dual cultures) on water agar plates, a hyphal interaction experiment and a modified double host-range experiment. Almost all inter- or intraisolate pairings of Clonostachys isolates showed growth inhibition zones and did not show free hyphal intermingling. A hyphal interaction experiment on water agar demonstrated that the aggressiveness of a Clonostachys isolate and its susceptibility to mycopar- asitism were unrelated phenomena. However the level of aggressiveness and/or susceptibility of an isolate were largely dependant on the isolate with which it was challenged. The degree of growth-inhibition caused by an isolate was unrelated to the hyphal damaged it caused or received. In the double host-range experi- ment all possible pairs from four Clonostachys isolates were inoculated in different ratios (10 000-fold range) on plates precolonized with one of two P. palmivora isolates. The results showed that antagonistic capabil- ities of certain combinations were affected by the Clonostachys isolates. The primary host, P. palmivora, did not affect antagonistic capabilities; whereas inocu- lum ratio did. Of note, it was not possible to predict the outcome of the double host range on the basis of the results of the hyphal interaction experiment. In conclusion the competitive abilities of Clonostachys isolates depend on the partner with which they are applied and less on resource availability. The double host-range test as developed here might provide the most representative tool to date to test compatibility of fungal antagonists to be used in biocontrol inocula. However the link between the results of the double host-range test and field efficacy of biocontrol inocula remains to be investigated.

Biocontrol agents of numerous insect pests and fungal pathogens exist but virtually nothing is known about their interaction if used simultaneously. Our objective was to investigate the compatibility of the entomopathogens Beauveria bassiana, Metarhizium anisopliae and Paecilomyces fumosoroseus, and the broad host-range mycoparasites Clonostachys spp., Trichoderma harzianum and Lecanicillium lecanii. In vitro host-range tests revealed that M. anisopliae was highly susceptible to all mycoparasites tested. B. bassiana was attacked by Clonostachys rosea, and P. fumosoroseus. was resistant to mycoparasites. M. anisopliae but not P. fumosoroseus killed nymphs of Bemisia tabaci in bioassays. B. bassiana and M. anisopliae proved lethal to Cosmopolites sordidus, Diatraea saccharalis and Sitophilus oryzae. Coapplication of mycoparasites with entomopathogens did not affect their biocontrol efficacy in vivo, although the reisolation success of entomopathogens could be significantly reduced, especially from smaller insect species. Trichoderma spp. were reisolated from mycoparasite-treated insects more frequently than C. rosea. The coapplication of the highly susceptible M. anisopliae generally enhanced mycoparasite recovery. Mycofungicide preparations caused some insect mortality but less than a copper hydroxide fungicide which is still permissible in organic agriculture. We concluded that the tested entomopathogens and mycoparasites are compatible elements of integrated pest management.