Seasonal abundance of Tuberolachnus salignus and its effect on flowering of host willows of varying susceptibility

Abstract

The giant willow aphid Tuberolachnus salignus Gmelin is a large phloem‐feeding insect which colonizes the stems of willow trees. This aphid is a new invasive species in New Zealand and there is limited knowledge of its inter‐annual population patterns and the damage it can cause to willow hosts. Our study investigated the T. salignus population dynamics and its effects on the flowering parameters of fifteen willow species and hybrids in a field trial. The aphid population levels were found to vary among the willow species and hybrids. Based on the aphid population levels, the willow species and hybrids were classified as resistant, moderately resistant, susceptible or highly susceptible. T. salignus infestation had no effect on the flowering of resistant and moderately resistant willows, but significantly delayed the flowering time, extended the flowering duration, and decreased the catkin length in susceptible species and hybrids. Interestingly, aphid infestation was found to increase the catkin number and total floral output of some willow species and hybrids. It can be concluded that aphid populations and their effects on flowering are host‐specific, with large differences between resistant and susceptible host plants.

The giant willow aphid (Tuberolachnus salignus) and its effects on the survival and growth of willows

“…The depletion of carbohydrate reserves in autumn has been observed with woolly poplar aphid (Phloeomyzus passerinii) infestation of Populus tremuloides, and bark of Populus tremuloides in the autumn, as a result of woolly poplar aphid (P. passerinii) infestation, were associated with reduced stem radial growth of the plants during the following season. The largest reductions in growth during the second season occurred in the cultivars of S. candida and S. viminalis that had large aphid populations; the same plants showed delayed and extended spring flowering, and reductions in flowering catkin size (Tun et al, 2021). By contrast, the S. eriocephala and S. lasiolepis × viminalis cultivars had no reduction in growth during the second season, had small populations of aphids that produced little honeydew (Tun et al, 2020), and showed no delays in spring flowering (Tun et al, 2021).…”

“…The largest reductions in growth during the second season occurred in the cultivars of S. candida and S. viminalis that had large aphid populations; the same plants showed delayed and extended spring flowering, and reductions in flowering catkin size (Tun et al, 2021). By contrast, the S. eriocephala and S. lasiolepis × viminalis cultivars had no reduction in growth during the second season, had small populations of aphids that produced little honeydew (Tun et al, 2020), and showed no delays in spring flowering (Tun et al, 2021).…”

“…In the S. candida cultivar, plant mortality occurred when spring bud break was not initiated. In those plants with aphids where spring bud break occurred, there was delayed and extended flowering, and a reduction in the size of the flowering catkins (Tun et al, 2021). The S. viminalis cultivar had large aphid populations in the first and second growing seasons, but in contrast to S. candida, the plant mortality occurred late in the second season in the treatment with aphids.…”

Honeydew production by the giant willow aphid (Tuberolachnus salignus, Hemiptera: Aphididae) and its effect on foraging yellowjackets (Hymenoptera: Vespidae)

“…and Salix schwerinii E. Wolf in New Zealand. 33 Additionally, Tun et al 34 found that in New Zealand, GWA on Salix fragilis has medium levels of aphid persistence on willows, compared to other species such as Salix viminalis L. This species can persist 30% more time at high levels, suggesting that host-plant nutritional quality could also affect GWA persistence. In our region, GWA appears to have a shorter permanence of willows than other parts of the world.…”

Ecological aspects of volatile organic compounds emitted by exotic invasive plants

“…Another possible scenario is the interaction between alien invasive plants and insects, which is predicted to increase due to global trade and climate change (Johnson et al, 2009). A series of studies (Tun et al, 2020(Tun et al, , 2021(Tun et al, , 2022Jones et al, 2021) investigated the resistance, growth, reproduction, and VOC emission of 15 introduced willow clones in New Zealand in response to the attack of the giant willow aphid Tuberolachnus salignus (of Asian origin). These willow clones were mainly from Europe and North America, with some having invasive traits.…”