FB 11 Ökologische Agrarwissenschaften

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Agroecological pest control through mulch in potatoes - Delayed population development of Leptinotarsa decemlineata [Dataset]
(Universität Kassel) Weiler, Christiane
Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is one of the most relevant pests in potato cultivation and even in organic potatoes, it is often managed using pesticides. Mulching potatoes represents an alternative to reduce egg masses and larvae of L. decemlineata. In three 4-fold replicated field trials with unmulched control plots (a) in comparison to plots mulched with grass-clover (b) or triticale-vetch (c) the effects on L. decemlineata population dynamics were assessed. In 2020 and 2021, larvae and their respective developmental stage of L. decemlineata were recorded twice weekly on 30 marked potato plants per plot. In 2022 assessments took place 3 times during the season on 16 plants per plot. To examine the influence of changed microclimatic conditions due to mulching, temperature loggers were installed 15 cm above the canopy and belowground. The number of larvae of L. decemlineata was significantly reduced on average by 65 % in the mulched treatments and higher larval stages occurred later and in lower numbers compared to the unmulched plots. In 2022, also a significant reduction of second-generation adults of L. decemlineata could be observed. During warm and hot weather, the canopy temperatures in the mulched plots considerably exceeded those of the unmulched plots, often reaching peak temperatures well above the optimum for L. decemlineata development. Mulching leads either to delayed or reduced immigration of adult beetles as well as potentially to slower egg and larval development.
Colorado potato beetle Leptinotarsa decemlineata avoids transferred organic mulch - insight from a mark release trial [Dataset]
(Universität Kassel) Weiler, Christiane
The Colorado potato beetle Leptinotarsa decemlineata (Say) (CPB) is one of the most relevant pests in potato cultivation. Even in organic potatoes, CPB are often managed using organically certified insecticides that may also affect non-target organisms and increase the risk of insecticide resistance. Applying transferred organic mulch to potatoes has been shown to reduce egg masses and larvae of CPB, however, the underlying mechanisms remain unclear. To assess effects of mulch on initial infestation of CPB, marked individuals were released in the field between plots with transferred organic mulch and plots with bare soil and counted after 12 h in 2021 and 2022. In 2022, one additional assessment was carried out 72 h after release and eggs and larvae where assessed after 10 days. More than 75% of CPB adults preferred the unmulched plots, a major reason for the reduction of eggs and larvae in mulched potatoes found in previous field trials. Barrier effects, olfactory disruption or disorientation could be responsible for the reduction.
Mulching effects on nutrient contents of potato foliage and Colorado potato beetle fitness [Dataset]
(Universität Kassel) Weiler, Christiane
Application of organic mulches has repeatedly been shown to reduce infestation with Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), the Colorado potato beetle (CPB). In order to determine if the nutritional status of potatoes as affected by mulch could explain the mulch effects in potatoes against CPB, we determined potato leaf nutrient composition in unmulched control plots and plots mulched with grass-clover or triticale-vetch and assessed mulch effects on CPB damage and development in the field during three years and under controlled conditions. In mulched plots, foliar Mo, Cl, and K contents were consistently higher than without mulch and leaf damage by CPB was reduced significantly. In addition, increased B contents were associated with undamaged plant material while higher Zn contents were associated with leaves damaged by CPB. Under controlled conditions, CPB fitness was not affected by mulch application. Overall, reduced CPB damage could not be clearly attributed to altered foliar nutrient contents due to mulching. It is thus more likely that CPB reductions in mulched systems are due to mechanisms other than an altered nutrient balance.