Does host plant quality constrain the performance of the Parthenium beetle Zygogramma bicolorata?

Abstract

In South Africa, the leaf-feeding beetle, Zygogramma bicolorata Pallister (Coleoptera: Chyrsomelidae), was released in 2013 against the invasive annual herb Parthenium hysterophorus L. (Asteraceae: Heliantheae). Poor field establishment and variable incidence of the beetle, during the first few years after release, have led to concerns surrounding potential constraints, including host plant quality. This study assessed the influence of high, medium and low host plant quality, as influenced by fertiliser application, on the survival, development and fecundity of Z. bicolorata. Although egg to adult survival was high (∼80%) and did not differ between plant quality treatments, larvae developed fastest on plants of high and medium quality. Larval feeding was highly damaging, reducing the growth, reproduction and biomass of P. hysterophorus in all three plant quality treatments. Fecundity was associated with plant quality, with larger, more fecund females developing on higher quality plants. Overall, this research may aid current mass-rearing efforts, further field research to verify these findings and direct the selection of more suitable release sites for Z. bicolorata in South Africa.

Parthenium avoids drought: Understanding the morphological and physiological responses of the invasive herb Parthenium hysterophorus to progressive water stress

“…Severe reductions in herbicide efficacy are known when applied to water-or drought-stressed plants (Varanasi et al 2016), meaning that whilst water-stressed, P. hysterophorus is unlikely to be affected by pre-or post-emergent registered herbicides. Likewise, water-stressed P. hysterophorus plants show decreased RLWC, nutrients J o u r n a l P r e -p r o o f (chlorophyll) and growth, making it harder to sustain large and effectively damaging populations of biocontrol agents in the field (Dhileepan et al 2000;Cowie et al 2019). Ectophages and leafaffecting agents such as the leaf-feeding beetle Zygogramma bicolorata (Coleoptera: Chrysomelidae) or the Puccinia fungal pathogens may be particularly sensitive to water-stressed P. hysterophorus plants, more so than endophagous biocontrol agents.…”

“…Leaf number was recorded as the total number of fully expanded leaves present on the plant, excluding small leaflets. Leaf area was calculated as per Cowie et al (2019) using the length and width of each fully expanded leaf present on the plant: Equation 1.…”

Implications of elevated carbon dioxide on the susceptibility of the globally invasive weed, Parthenium hysterophorus, to glyphosate herbicide

“…Leaf production was taken as the number of fully expanded leaves, excluding any secondary leaflets, present on the plant. Leaf area was calculated (cm 2 ) as per Cowie et al . in which the length and width of all fully expanded leaves were measured and used to gain total leaf area per plant.…”

“…Prolific seed production often results in the formation of extensive and long‐lasting seedbanks, which can exceed 100 000 seeds/m 2 and remain viable for more than 5 years, making management challenging and costly . Although biological control is viewed as the long‐term solution in South Africa, many agricultural and commercially valued areas remain focused and reliant upon herbicidal controls to effectively manage P. hysterophorus invasions nationally and internationally.…”

Plant Chemistry Determines Host Preference and Performance of an Invasive Insect

“…Biological invasions threaten global economic development and ecological and food security, especially when invasive pest species cause loss of crop yields (Huber et al, 2002;Pimentel et al, 2005;Worner and Gevrey, 2006). The introduction, establishment, and colonization of alien insect species are determined by many factors, for example, host availability and food quality (Burrack et al, 2013;Kenis et al, 2016;Cowie et al, 2019). In such invasive processes, host plant species can significantly influence adult oviposition preference and larval developmental performance of phytophagous insect (Abbes et al, 2016).…”