Bibliography
2021
© Oto Zimmermann
Authors
RNDr. Milan Řezáč, Ph.D., Pavel Saska
Abstract
Intenzifikace zemědělství s sebou přinesla závislost produkce na agrochemikáliích. Pesticidy pomáhají regulovat škůdce, ale zároveň negativně ovlivňují i řadu užitečných organismů. Čím intenzivněji je v zemědělství používáme, tím více zbavujeme agroekosystémy přirozených funkcí, včetně regulace škůdců jejich predátory. Abychom tento proces alespoň zpomalili, je nezbytné studovat dopady jednotlivých pesticidů na užitečné organismy a na základě získaných informací navrhnout způsoby ochrany proti škůdcům v souladu s principy integrované ochrany rostlin (IOR).

2020
© Oto Zimmermann
Authors
RNDr. Jiří Skuhrovec, Ph.D., RNDr. Milan Řezáč, Ph.D., Pavel Saska
Abstract
Carabids are generalist predators that contribute to the agricultural ecosystem service of seedbank regulation via weed seed predation. To facilitate adoption of this ecosystem services by farmers, knowledge of weed seed predation and the resilience of seedbank regulation with co-varying availability of alternative prey is crucial. Using assessments of the seedbank and predation on seed cards in 57 cereal fields across Europe, we demonstrate a regulatory effect on the soil seedbank, at a continental scale, by groups formed of omnivore, seed-eating (granivore + omnivore) and all species of carabids just prior to the crop-harvest. Regulation was associated with a positive relationship between the activity-density of carabids and seed predation, as measured on seed cards. We found that per capita seed consumption on the cards co-varied negatively with the biomass of alternative prey, i.e. Aphididae, Collembola and total alternative prey biomass. Our results underline the importance of weed seedbank regulation by carabids, across geographically significant scales, and indicate that the effectiveness of this biocontrol may depend on the availability of alternative prey that disrupt the weed seed predation.

2019
© Oto Zimmermann
Authors
RNDr. Milan Řezáč, Ph.D., Pavel Saska, Stanislav Korenko
Abstract
Neonicotinoids are thought to have negligible repellent or anti-feeding effects. Based on our preliminary observations, we hypothesized that the contamination of spider prey with commonly used neonicotinoids has repellent or feeding deterrent effects on spiders. We tested this hypothesis by providing prey treated or not with field-realistic concentrations of neonicotinoids to the spiders and determining the number of (a) killed only and (b) killed and eaten prey. We exposed adult freshly molted and starved Pardosa agrestis, a common agrobiont lycosid species, to flies treated with neonicotinoids (acetamiprid, imidacloprid, thiacloprid and thiamethoxam) at field-realistic concentrations or with distilled water as a control. There were no effects of the exposure of the prey to neonicotinoids on the number of flies captured. However, the spiders consumed less of the prey treated with neonicotinoids compared to the ratio of control prey consumed, which resulted in increased overkilling (i.e., killing
without feeding). In female P. agrestis, the overkilling increased from only 2.6% of control flies to 25–45% of neonicotinoid-treated flies. As the spiders avoided consuming the already captured neonicotinoid-treated prey, the sublethal effects of neonicotinoids extend beyond the simple attractivity/deterrence of the prey itself. The present study demonstrated that prey overkilling serves as a physiological response of spiders to the contact with the prey contaminated with agrochemicals. We speculate that primary contact with neonicotinoids during prey capture may play a role in this unexpected behavior.

2019
Authors
RNDr. Jiří Skuhrovec, Ph.D., RNDr. Karel Tajovský, CSc., RNDr. Milan Řezáč, Ph.D., Pavel Marhoul, Pavel Saska

2013
Authors
RNDr. Antonín Kůrka, Pavel Moravec, Pavel Saska, Pavel Vonička