Aims: Five bacterial strains belonging to Bacillus subtilis, Pseudomonas fluorescens and Ps. corrugata and two fungal strains belonging to Trichoderma viride and Gliocladium virens were evaluated for their efficacy in controlling sugar beet and cucumber damping‐off caused by Pythium ultimum. Methods and Results: The in vitro antagonistic activity of bacteria against various Pythium spp. was evaluated with dual cultures in various media. Pseudomonas strains inhibited the pathogen better than Bacillus strains. To identify potentially useful antagonist combinations, dual compatibility of antagonists was also evaluated, based on growth in two liquid media containing substrate previously used by other antagonists. Four pairs of bacteria were selected. Sugar beet damping‐off biocontrol was attempted with bacterial seed treatments (individually and in pairs). Cucumber damping‐off biocontrol was attempted with bacterial seed treatments and bacterial and fungal compost treatments. In sugar beet, satisfactory biocontrol was only achieved with Pseudomonas antagonists. Antagonist combinations did not show any superior biocontrol ability to individual antagonists and compatibility of bacteria in vitro did not correlate with compatibility in vivo. Bacterial seed treatments and fungal compost treatments failed to control cucumber damping‐off. Better biocontrol in cucumber was achieved when bacterial antagonists were applied by drenching or by coating seed with bacteria in a peat carrier. Conclusions: Pseudomonas antagonists were superior to Bacillus antagonists in controlling damping‐off in cucumber and sugar beet. Pseudomonas peat inocula maintained a good shelf‐life 2 years after preparation. Significance and Impact of the Study: Pseudomonas peat formulations have the potential for development into commercial biopesticides.

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The efficacy of Milsana Ò VP 1999 and 2000 (a formulated plant extract of Reynoutria sachalinensis), known to induce resistance to powdery mildew on cucumbers, was tested against Leveillula taurica (Le´v.) Arn. on greenhouse tomato. In four out of five trials, Milsana Ò achieved a disease reduction ranging from 42.2 to 64.6%. In one trial only, its efficacy was exceptionally low (23%). Application rates and disease pressure proved to be the main factors affecting the level of control. Milsana Ò was significantly less effective than fungicides (alternated DMIs and penconazole) in situ. In contrast, Milsana Ò was equally effective to wettable sulphur indicating that its effect was rather preventive than curative. The level of efficacy achieved by either Milsana Ò or fungicides did not result in a significant increase of yield. Laboratory tests showed that Milsana Ò (VP 1999) had a direct effect on conidial germination. Whether this effect significantly contributes to its field efficacy, remains to be elucidated. Overall, results indicate that Milsana Ò could play an important role in disease management of powdery mildew in organic and low input tomato production.

SUMMARY During recent years a new disease has been noticed on tomatoes grown in Polythene greenhouses in Crete. Early symptoms are yellowing of the lower leaves, and a yellow brown discoloration of the pith and stem xylem. As leaves wilt and die there is progressive yellowing towards the top of the plants. A progressive disintegration of the cortical tissues follows which results in a soft rot and a longitudinal splitting of the stem running mainly upwards. Soft rot of the fruits rarely appears. Severely infected plants may wilt and die, but other less affected plants often survive and yield normally. Very vigorous plants grown under humid conditions are more susceptible. Often more than 20% of the plants are infected. Isolations were made from stem (xylem, cortex and pith), from leaf xylem and from fruits of infected tomato plants collected throughout the island from 1979 to 1985. Bacteria of the genus Erwinia and Pseudomonas were consistently isolated. On the basis of physiological and biochemical characters of 49 representative pathogenic isolates, 22 were identified as Erwinia carotovora subsp. carotovora, 10 as Erwinia carotovora subsp. atroseptica, four as Pseudomonas viridiflava and 13 as Pseudomonas fluorescens biotype I. All disease symptoms were reproduced when artificial inoculations were made with the above isolates in the laboratory (20°C and 100% r.h.) on 3–4 week tomato plants and in a commercial greenhouse on 4–5 months tomato plants. Bacteria used for inoculations were reisolated. Results indicated that the disease symptoms as described may be caused by four different bacteria species.

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