Direct and indirect impacts of different water regimes on the invasive plant, alligator weed (Alternanthera philoxeroides), and its biological control agent, Agasicles hygrophila

Abstract

Invasive weeds are broadly affected by natural disturbances, such as flooding and drought. While these disturbances can directly affect the outcome of a plant invasion, they can also indirectly affect the population dynamics of the invasive plant's natural enemies. However, how flooding and drought alter the interactions of invasive plants with their natural enemies and what impact these events have on the invasive plants have been little studied. This study reports on the effects of flooding and drought on the invasive plant, Alternanthera philoxeroides, its biological control agent, Agasicles hygrophila, as well as their interactions in field and laboratory experiments. It was found that drought decreased the stem length and number of internodes of A. philoxeroides, while flooding reduced the number of branches, relative to those in the control treatments. Both drought and flooding significantly decreased the total number of ramets, as well as the root and shoot mass of this weed, compared to a less drastic water regime. Drought indirectly suppressed the population growth of Ag. hygrophila by decreasing plant palatability. Indeed, herbivory by Ag. hygrophila had little impact on A. philoxeroides under drought conditions. The results of this study suggest that drought can reduce the biological control of A. philoxeroides indirectly by interrupting plant-insect interaction. Therefore, understanding how invasive plants and enemies interactively respond to seasonal climatic disturbances will provide important information for improving and predicting the management efficiency of invasive weeds.

Bottom‐up effects of drought on the growth and development of potato, Leptinotarsa decemlineata Say and Arma chinensis Fallou

“…Drought indirectly affects the growth, development, population reproduction and other biological characteristics of natural predators 27,33,34 . Drought has been reported to have negative impacts on the population of natural predators, such as reducing the survival rate of Meteorus pulchricornis (Wesmael) and lowering the longevity and fecundity of Anagrus nilaparvatae 41–43 .…”

“…32 Drought may also indirectly affect the growth and reproduction of natural predator populations. 27,33,34 For example, drought reduced the parasitic rate of Aphidius ervi. 35 However, this effect may also be beneficial; for instance, drought increased the parasitic rate of the natural parasitoids of Stephensia brunnichella.…”

“…However, the effect may also be beneficial; drought increased the population of Eotetranychus willamettei 32 . Drought may also indirectly affect the growth and reproduction of natural predator populations 27,33,34 . For example, drought reduced the parasitic rate of Aphidius ervi 35 .…”

Weeds and their Management under Changing Climate: A Review

“…Similarly, Allen et al (2014) reported that changing environmental temperature may create constraints on reproduction and development of Cyrtobagous salviniae, BCA of Salvinia molesta. Wei et al (2015) also studied about the effect of different water regimes on Agasicles hygrophila, BCA of Alternanthera philoxeroides and suggested that drought can reduce the biological control of weed indirectly by interfering with plant-insect interaction.…”

Activated Carbon Prepared from Alternanthera philoxeroides Biomass by One-step K2CO3 Activation

“…Alligator weed can also cause the death of fish and native plants and provides a favorable habitat for mosquitoes (Bhattacherjee et al 2014). The control and elimination of AP includes biological (Sun et al 2010;Wei et al 2015), chemical, and physical methods (Schooler et al 2008). Biological control is a valuable and environmentally friendly method of weed control.…”