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Lymantria dispar L. is an invasive, non-native defoliating Lepidopteran established in North America that feeds on forest and urban trees. While many products are available to manage L. dispar post-emergence, few exist to prevent egg hatch when applied to egg masses. Here, we present the results of 3 separate experiments aimed at determining the efficacy of pre-emergent insecticides against L. dispar egg hatch. We found that the labeled rate (1:1) of Golden Pest Spray Oil (GPSO; AI: 93% soybean oil) can prevent L. dispar larvae from emerging in both field and lab assays. In large public spaces, we found that this treatment was ineffective at preventing L. dispar emergence or defoliation. Acelepryn (AI: 18.4% chlorantraniliprole) resulted in some suppression of egg hatch at a very low rate (.06 ml/ 3.8 liter) in both lab and field settings and the efficacy of higher rates should be further investigated. We also tested GPSO against Lepitect (97.4% acephate) in a public area that also received a Foray 48B (12.65% Bacillus thuringiensis, subsp. kurstaki) aerial application. On large oak trees in public areas, GPSO and Lepitect were not effective at reducing defoliation. Dormant pesticide applications generally reduce the risk of affecting negatively predator and parasitoid communities and are therefore desirable. Lymantria dispar pre-egg hatch applications will not work in every situation but should be considered as part of an integrated pest management (IPM) strategy for individual homeowner trees where thorough coverage can be obtained. [ABSTRACT FROM AUTHOR]

Although many non‐native species arrive in novel environments, only a fraction successfully establish. A crucial factor affecting the colonization process of invading species is propagule pressure. The positive association between propagule pressure and colonization probability is driven both by stochastic dynamics and the 'Allee effect'. Although the role of Allee effects in invading populations is theoretically compelling, they are difficult to quantify in the field because the earliest phases of biological invasions are typically not observed.We conducted parallel studies using two species of bark beetles, Hylurgus ligniperda in New Zealand and Ips pini in North America, to (i) assess the role of propagule pressure on colonization success, (ii) empirically test for Allee effects and (iii) estimate Allee thresholds. We evaluated each of these factors by experimentally testing the effect of propagule pressure (numbers released) on simulated tree colonization success in two different settings: (1) field conditions where beetles could disperse freely and (2) enclosed cages where dispersal loss was prevented.Colonization success was positively associated with numbers released (i.e. propagule pressure) for both species, though colonization occurred at lower numbers for H. ligniperda than for I. pini. A demographic Allee effect was only detected in H. ligniperda and the Allee threshold was smaller when beetles were released 1 m from host billets than when they were released 10 m away. Greater colonization success at lower release densities may explain the invasion success of H. ligniperda worldwide. Higher release densities required for successful colonization may explain why I. pini is a poor establisher.Synthesis and applications. Our results linking invasion failure to small founding population densities generally support the theoretical literature on the role of propagule pressure and Allee effects in biological invasions. Agencies such as the International Plant Protection Committee (IPPC) setting phytosanitary measures such as the International Standards for Phytosanitary Measures No. 15 (ISPM 15) should consider using the colonization thresholds estimated here to limit numbers of colonizing individuals below invasion thresholds. Additionally, agencies conducting trapping efforts at ports‐of‐entry should be aware of these thresholds and widely report when trapping numbers exceed these thresholds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pinus sylvestris exhibited higher levels of monoterpenes than P. ponderosa following artificial wound inoculation with Grosmannia clavigera. • Induction of limonene, 3-carene, and myrcene was greater in P. sylvestris than P. ponderosa. • The chemical induced response of P. sylvestris to artificial wound inoculation was similar to that induced by wounding alone. • P. sylvestris may provide one alternative plantation species for timber production in the Great Lakes Region following mountain pine beetle incursion. Mountain pine beetle (MPB, Dendroctonus ponderosae) is a destructive pest of pine forests in western North America. This insect is currently expanding its range across the Canadian boreal forest towards eastern North America, where a suite of novel pine species will be encountered. One species of pine without prior association with MPB is Pinus sylvestris (Scots pine), which is native to Europe and naturalized in parts of central and eastern North America. Here, we take advantage of a unique opportunity in the Black Hills of South Dakota where an isolated, planted, and mature stand of P. sylvestris and native Pinus ponderosa (ponderosa pine) co-exist within the range of MPB. We conducted a punch-inoculation experiment to determine the chemical response of P. sylvestris from a blue-stain fungus associated with MPB, Grosmannia clavigera , and compared the response to that of P. ponderosa. We found that P. sylvestris had a higher localized monoterpene response than P. ponderosa in response to inoculation, but a lower sesquiterpene response. Among the significant monoterpenes associated with MPB behavior, limonene, 3-carene, and myrcene had a larger localized response in P. sylvestris than P. ponderosa ; lower levels of 4-allylanisole were found in P. sylvestris. Fungal inoculation did not induce a stronger terpenoid response than mechanical wounding without inoculation, indicating that P. sylvestris responds to mechanical damage similarly as to fungal inoculation. Pinus sylvestris may provide one alternative plantation species for timber production in the Great Lakes Region following mountain pine beetle incursion, however, more evaluation is needed to determine the role of this species in future plantings. [ABSTRACT FROM AUTHOR]

The establishment and spread of Sirex noctilio F. (Hymenoptera: Siricidae), in northeastern North America necessitates reliable monitoring methods for this alien woodwasp pest of Pinus. The native congener, Sirex nigricornis F., is common across the eastern U.S.A. and has been studied as a proxy for S. noctilio. Predicting the emergence of S. noctilio is important for guiding monitoring efforts., Degree-day models have been developed to predict flight phenology of S. noctilio and S. nigricornis across eastern North America. These model parameters were tested against three years of S. nigricornis collections from two locations in Arkansas. Neither of the proposed models accurately predicted emergence., The emergence of females for both S. noctilio and S. nigricornis was significantly negatively correlated with minimum and maximum temperature, indicating that emergence increases when minimum and maximum temperatures decrease. These results suggest that, as S. noctilio spreads south, where higher mean temperatures are present, it will emerge later in the season as the temperatures decline compared with the current northeastern population., We propose that monitoring for the spread of S. noctilio in the southeastern U.S.A. should begin slightly before daily temperatures are expected to decline (i.e. mid-September). [ABSTRACT FROM AUTHOR]