Arthropods in agroecosystems are frequently exposed to two stressors: chemical pesticides and extreme high temperature events due to climate warming. Studies dealing with the temperature-dependent toxicity of pesticides on arthropod pests clearly indicate the interaction of these two stressors, whereas similar studies on natural enemies are rare. Two predatory mite species, Typhlodromus pyri and Amblyseius andersoni, occur frequently in organic and integrated apple orchards in Austria; the former is highly dominant in both orchard types, and the latter is present in moderate numbers in integrated-, but is rare in organic orchards. Fungicides are the most commonly used pesticides in both systems; sulphur applications are dominant in organic orchards and synthetic fungicides in integrated orchards. We exposed the two species to fungicides and heat, to verify the following assumptions: the mortality of A. andersoni is higher than that of T. pyri when exposed to sulphur, and heat intensifies this negative effect on A. andersoni. The populations of A. andersoni and T. pyri were derived from extensive orchards (orchard meadows), organic and integrated apple orchards. Single eggs from each population of A. andersoni and T. pyri were placed onto bean leaf discs, which were then treated with either water (control), Curatio (active substance: calcium-polysulfide), or Delan WG (dithianon). Then they were exposed to either mild- or extreme heat waves until the protonymphal stage. Survival and development of the eggs and larvae were evaluated. The preliminary results indicate that there were no population-specific effects on survival and development. Delan WG did not affect the survival and development of the mites, independent on their species affiliation. Pooled over heat, the exposure to Curatio led to higher mortality rates in A. andersoni (87%) compared to T. pyri (55%). Heat stress and exposure to Curatio increased the mortality in both species from 80% (A. andersoni) and 37% (T. pyri) under mild heat waves to 92% and 72% under extreme heat waves; irrespective of the species. Extreme heat and exposure to Curatio sped up and decelerated the development, respectively. Thus, the increase of heat events due to climate warming in combination with the use of sulphur-based fungicides may lower the diversity and population densities of predatory mites in permanent cultures such as orchards and vineyards in the next decades. The research was funded by the Austrian Climate and Energy Fund (48407317).