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Recent outbreaks of ‘CandidatusPhytoplasma solani’ resulted in severe losses in potatoes, vegetable crops and grapevines in certain regions of Austria and constituted a major challenge for seed potato production. Therefore, the effects of various insecticides and insect deterrents on pathogen spread were studied both in laboratory and field experiments from 2018 to 2021. In laboratory transmission experiments, field captured Hyalesthes obsoletuswere caged on differently treated Catharanthus roseusfor five days.The insecticides lambda-cyhalothrin, deltamethrin, esfenvalerate, acetamiprid and chlorpyriphos showed the most rapid impact on insect survival and fully prevented phytoplasma transmission. The particle film forming products kaolin and diatomaceous earth had some effect. A transfer of the promising laboratory results to potato fields, however, was achieved to a limited extent only. Treatments with pyrethroids and acetamiprid every 8–10 days over the flight period of H. obsoletusroughly halved the number of symptomatic plants and tubers in case of moderately susceptible varieties and moderate infection pressure. In the event of susceptible varieties and high disease pressure, treatment effects were hardy discernible. In practical terms, the experiments indicate that insecticide applications alone are not sufficient to mitigate the disease. Spraying of diatomaceous earth and mineral oil did not affect disease incidence in the field.

Pear decline, induced by the phytoplasma 'CandidatusPhytoplasma pyri', transmitted by pear psyllids, is one of the most devastating diseases on Pyrus communisin Europe and North America. Investigations of pear psyllids in 4 pear orchards in lower Austria showed the presence of Cacopsylla pyri, C. pyricolaand C. pyrisugaat all locations. PCR analyses revealed overall phytoplasma infection rates for C. pyriof 5.4%, for C. pyricola,of 4.6%, for C. pyrisugaremigrants of 9.6% and for C. pyrisugaemigrants of 0%. The rates of PCR-positive C. pyriand C. pyricolaindividuals varied greatly in the course of the year, and the highest infection rates were observed in late summer, autumn and in late winter. In transmission experiments with healthy pear seedlings, winterform individuals of C. pyri and C. pyricolatransmitted the pathogen to 19.2% (5 out of 26) and 4.8% (2 out of 41) of the test plants, respectively. The vectoring ability of C. pyrisugawas experimentally proven for the first time, and in transmission experiments with remigrants, 9.5% (2 out of 21) of the pear seedlings were infected. Our data indicate a significant risk of pathogen transmission in pear orchards during the greater part of the year, especially in late winter, early spring and autumn. Multilocus sequence analysis by aid of the genes aceFand impallowed the discrimination between 15 phytoplasma types. Three so far undescribed aceFgenotypes and four undescribed impgenotypes were identified.

Drosophila suzukiiMatsumura (Diptera: Drosophilidae) is a significant pest in soft fruits such as elderberries. Laying of eggs into fruits shortly before harvest results in fruit decay and quick collapse. Practically oriented field trials were set up in three commercial elderberry farms in Styria and Lower Austria from 2018 to 2020 to test alternative, sustainable pest control options. The effect of combinations of diatomaceous earth, paraffin oil, gum arabic, Ca(OH)2and maltodextrin with wetting agents based on orange oil/alcohol ethoxylate, polyetherdimethylsiloxanes and terpene oligomers was compared to currently used conventional insecticide treatments (spinosad, lambda-cyhalothrin, acetamiprid) and to an untreated control. Three to five treatments per orchard were applied from the beginning of infestations until harvest. Microscopic analyses of the berries and visual inspections of the umbels allowed evaluation of oviposition, larval development and overall conditions of the umbels for the individual treatments. Diatomaceous earth combined with a wetting agent based on orange oil/alcohol ethoxylate had the most promising effect: the treatment significantly reduced oviposition, reduced instars in berries and improved the conditions of the umbels in all test years as compared to the control. Moreover, Ca(OH)2and gum arabic combined with polyetherdimethylsiloxanes lead to a significant reduction of oviposition. Development of flies in the berries was identified as major cause for premature berry drop. These findings may provide a basis for the application of alternative control strategies.