Journal: Biological Control
Location: ?

The invasive Japanese knotweed has 180 natural arthropod enemies; the sap-sucking jumping plant louse Aphalara itadori may be the first authorised for use in the European Union. 146,885 A. itadori eggs were laid, and it took 33 days to go through 5 nymph stages at 23oC. 1.52% of eggs laid on 87 species or varieties of plants were not on Japanese knotweed, but these did not become adults. When nymphs were transferred to Maidenhair vine, 7% developed to adulthood.

Japanese knotweed – Fallopia japonica
Maidenhair vine – Meuhlenbeckia complexa

Shaw RH, Bryner S, Tanner R, 2009. “The life history and host range of the Japanese knotweed psyllid, Aphalara itadori Shinji: Potentially the first classical biological weed control agent for the European Union” Biological Control 49(2): 105-113, doi:10.1016/j.biocontrol.2009.01.016
Affiliations: Commonwealth Agricultural Bureaux International (CABI), Swiss Federal Institute of Technology (ETH)

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Journal: Science
Location: ?, USA

It is suggested that some pea aphids, a crop pest, are tolerant to heat stress because of bacterial symbionts, Buchnera aphidicola. Members of a strain of heat-sensitive pea aphids with only a non-resistant symbiont were put in 2x2x2m mesh cages, and heat shocks were simulated by putting plastic sheets over the cages (increasing temperature by ~5°C to what would normally affect pea aphid reproduction but still occur naturally). Introduction of predators does not necessarily cause the number of aphids to drop. The number of pea aphids was reduced when subjected to heat shocks, and the presence of 7-spot ladybird predators made no difference (X2 = 2.4, P > 0.5). However, when harlequin ladybirds were introduced, the effect of heat shock was alleviated (X2 = 41.8, P <10–6) because they only predate when population density of aphids is high.

In pairs of one green aphid clone and one red aphid clone, the population growth rate of both red heat-sensitive clones (0.243 ± 0.009) and green heat sensitive clones (0.269 ± 0.008) was greater than their green (0.214 ± 0.007, selection coefficient 0.25) and red (0.247 ± 0.010, selection coefficient 0.20) heat-tolerant counterpart, respectively. When subjected to heat shocks, the growth rate of heat-tolerant clones was notably greater for both green (0.234 ± 0.023 compared to 0.155 ± 0.027 in sensitive reds) and red (0.208 ± 0.031 compared to 0.129 ± 0.033 in sensitive greens) clones. Although the population growth rate was reduced in heat-sensitive clones upon heat shock, this was less than the decrease in growth of heat-sensitive clones (X2A = 12.1, P < 0.001; X2B = 6.96, P < 0.01). Thus rapid evolution of heat-tolerant pea aphid strains may occur if climate change causes more frequent heat shocks.

Pea Aphid – Acyrthosiphon pisum
Seven-Spot Ladybird – Coccinella septempunctata
Harlequin Ladybird – Harmonia axyridis

Harmon JP, Moran NA, Ives AR, 2009. “Species Response to Environmental Change: Impacts of Food Web Interactions and Evolution” Science 323(5919): 1347-1350, DOI: 10.1126/science.1167396
Affiliations: University of Wisconsin, and University of Arizona