No abstract

Summary Understanding the causes of population subdivision is of fundamental importance, as studying barriers to gene flow between populations may reveal key aspects of the process of adaptive divergence and, for pathogens, may help forecasting disease emergence and implementing sound management strategies. Here, we investigated population subdivision in the multihost fungus Botrytis cinerea based on comprehensive multiyear sampling on different hosts in three French regions. Analyses revealed a weak association between population structure and geography, but a clear differentiation according to the host plant of origin. This was consistent with adaptation to hosts, but the distribution of inferred genetic clusters and the frequency of admixed individuals indicated a lack of strict host specificity. Differentiation between individuals collected in the greenhouse (on Solanum) and outdoor (on Vitis and Rubus) was stronger than that observed between individuals from the two outdoor hosts, probably reflecting an additional isolating effect associated with the cropping system. Three genetic clusters coexisted on Vitis but did not persist over time. Linkage disequilibrium analysis indicated that outdoor populations were regularly recombining, whereas clonality was predominant in the greenhouse. Our findings open up new perspectives for disease control by managing plant debris in outdoor conditions and reinforcing prophylactic measures indoor.

The thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is among the most important pests of greenhouse crops in Europe and causes considerable damage to commercial rose crops. The usage of pesticides is associated with major problems, and thus the interest of implementing integrated pest management (IPM) for rose crops is increasing. One essential component of IPM is field monitoring/scouting. Growers use information gathered from scouting to select and schedule appropriate control tactics. Thrips populations were surveyed in 2005 and 2006 in a greenhouse planted with roses, Rosa x Hybrida in Southern of France. From April to August, thrips were counted using yellow sticky traps (YST), knock-down techniques [i.e., tapping flower heads (FT)] and actual counts of entire plants. Thrips abundance recorded using YST correlated well with abundance levels determined through FT or actual counts (whole plant). Our results demonstrate that it is accurate to estimate thrips populations using YST in rose crops in greenhouse. Because YST takes at least twice less time than other monitoring methods, it could be used as a valid and easy monitoring technique in further development of IPM programs on roses. The possibility of setting a damage threshold using the data from the YST in the greenhouse is discussed.

We report the first detection of Trissolcus mitsukurii in France. More than 1860 sentinel egg masses of Halyomorpha halys (BMSB) were exposed in the field during the 2018–2020 period, and 12 specimens of T. mitsukurii emerged from one egg mass. Their taxonomic identification was confirmed both by morphological and molecular analysis. Trissolcus mitsukurii, similar to T. japonicus, is an egg parasitoid of BMSB in its area of origin in Asia, and both species are considered to be candidates for a classical biological control strategy against BMSB. Trissolcus mitsukurii was previously recorded in Italy where it is well established and widespread, and this may be the source of the French population. Possible permanent establishment and dispersion of T. mitsukurii in France should be monitored with emphasis on its potential effect on BMSB populations.