Agroecological Pest Control Through Mulch in Potatoes—Delayed Population Development of Leptinotarsa decemlineata

Abstract

Leptinotarsa decemlineata 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 by 65%, on average, in the mulched treatments and higher larval stages occurred later and in lower numbers compared to the unmulched plots. In 2022, a second-generation adults of L. decemlineata occurred whose numbers were significantly reduced by about 90% in the mulched plots. 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.