Gérald Chouinard

Apple (Malus domestica Borkhausen, Rosaceae, Rosales) orchards in Québec (Canada) have recently experienced increases in both stink bug populations and associated fruit damage. Even in the absence of the brown marmorated stink bug, Halyomorpha halys (Stål), stink bugs are jeopardizing Integrated Pest Management (IPM) programs since few environment-friendly control options are available. The objectives of this study were thus to (i) acquire knowledge on the seasonal abundance and species composition of Pentatomidae in 4 apple orchards using baited pyramid traps and beating trays and (ii) adapt and test an attract-and-kill (AK) strategy based on the knowledge acquired. Twenty species of stink bugs were collected over 3 years. Euschistus servus euschistoides (Vollenhoven) represented 80% of individuals captured overall and peaked at the end of August. Chinavia hilaris (Say), Euschistus tristigmus (Say), and H. halys came in second, third, and fourth place, respectively. Trece’s multi-species pheromone lures (Pherocon CSB+GSB+BMSB) commercialized for Euschistus sp., C. hilaris and H. halys respectively, caught the highest numbers of species and individuals, and were thus chosen for the AK trial. Lures were used in combination with sticky-coated yellow panel traps deployed at the periphery of the orchards. AK resulted in high stink bug mortality (numbers equivalent to ca. 10,000 individuals/ha) and damage was reduced by 25% overall for the 4 orchards, but not enough to translate into a statistically significant effect. Visual appearance of damage to fruit caused by phytophagous stink bugs on different cultivars is described.

To improve exclusion systems for fruit trees, insect nets of various types were evaluated for their permeability to different beneficial and pest species, under laboratory and field conditions. Pests studied were the apple maggot, Rhagoletis pomonella (Diptera: Tephritidae) and the spotted wing drosophila, Drosophila suzukii (Diptera: Drosophilidae). Beneficials were Aphidoletes aphidimyza (Diptera: Cecidomyiidae), Aphidius matricariae (Hymenoptera: Braconidae) and Aphelinus abdominalis (Hymenoptera: Aphelinidae). Mesh nets with five different apertures (square, rectangle, triangle, rhombus and hexagon) and six different sizes (from 0.4 to 2.8 mm) were 3D-printed from strands of polylactic acid and tested in the laboratory along with two commercially available nets made of polyethylene. The physical and behavioral characteristics of the six studied species affected their ability to cross the nets. For an equal size (open area), the intrusion rate was generally greater through the square- and/or hexagonal-shaped meshes. Rectangular-shaped apertures totally excluded the apple maggot in both laboratory and field trials, provided their shortest side did not exceed 1.9 mm. For the spotted wing drosophila, a maximum of 1.0 mm was similarly required for exclusion in the laboratory. The shape factor (length/width ratio) of the apertures appeared to affect net selectivity. Field trials confirmed that more aphid predators and leafroller parasitoids colonized trees covered with larger mesh nets (2.3 × 3.4 mm), while still excluding the apple maggot. Thus, for a similar aperture size (area), an elongated rectangular-shaped mesh appears to facilitate access for beneficials, while continuing to provide effective protection against apple pests.

To improve exclusion systems for fruit trees, insect nets of various types were evaluated for their permeability to different beneficial and pest species, under laboratory and field conditions. Pests studied were the apple maggot, Rhagoletis pomonella (Diptera: Tephritidae) and the spotted wing drosophila, Drosophila suzukii (Diptera: Drosophilidae). Beneficials were Aphidoletes aphidimyza (Diptera: Cecidomyiidae), Aphidius matricariae (Hymenoptera: Braconidae) and Aphelinus abdominalis (Hymenoptera: Aphelinidae). Mesh nets with five different apertures (square, rectangle, triangle, rhombus and hexagon) and six different sizes (from 0.4 to 2.8 mm) were 3D-printed from strands of polylactic acid and tested in the laboratory along with two commercially available nets made of polyethylene. The physical and behavioral characteristics of the six studied species affected their ability to cross the nets. For an equal size (open area), the intrusion rate was generally greater through the square- and / or hexagonal-shaped meshes. Rectangular-shaped apertures totally excluded the apple maggot in both laboratory and field trials, provided their shortest side did not exceed 1.9 mm. For the spotted-wing drosophila, a maximum of 1.0 mm was similarly required for exclusion in the laboratory. The shape factor (length / width ratio) of the apertures appeared to affect net selectivity. Field trials confirmed that more aphid predators and leafroller parasitoids colonized trees covered with larger mesh nets (2.3 x 3.4 mm), while still excluding the apple maggot. Thus, for a similar aperture size (area), an elongated rectangular shaped mesh appears to facilitate access for beneficials, while continuing to provide effective protection against apple pests.

Le granulovirus du carpocapse de la pomme (CpGV) et les parasitoïdes du genre Trichogramma sont des agents de lutte biologique du carpocapse de la pomme, mais leurs interactions sont inconnues. L’objectif de l’étude a été d’évaluer la compatibilité et la complémentarité de Trichogramma minutum et du CpGV. Des essais en laboratoire ont été menés la première année et des essais dans le verger ont été réalisés pendant deux ans avec les deux agents de lutte utilisés seuls ou en combinaison. Dans le laboratoire, le parasitisme a été réduit après que le CpGV a été appliqué sur les oeufs du carpocapse de la pomme, suggérant que les femelles parasitoïdes ont discriminé entre des oeufs recouverts de CpGV ou non. Au contraire, le CpGV n’a pas affecté le parasitisme causé par T. minutum dans le verger. Les deux agents de lutte ensemble ont causé 77 et 79 % de mortalité au carpocapse de la pomme dans le verger la première et la deuxième année respectivement. Nos résultats en verger montrent que l’effet combiné du CpGV et de T. minutum sur le carpocapse de la pomme est compatible. En conséquence, l’utilisation des deux agents de lutte biologique est une alternative prometteuse pour la lutte contre le carpocapse de la pomme dans les vergers de pommiers.

A group of commercial orchards from Quebec (Canada) was followed from 1977 to 2019 as part of a project to implement Integrated Pest Management (IPM) practices. Collected data comprised activity of major fruit pests (from monitoring traps), fruit damage at harvest and pesticide applications, from which the annual costs and impacts of protection programs over 42 years were calculated. Activity and fruit damage in commercial orchards were compared to patterns observed in a reference insecticide-free orchard. Some insects (European apple sawfly, codling moth, apple maggot) were more prevalent in the insecticide-free orchard than in commercial orchards, while others were more prevalent in commercial orchards (oblique-banded leafroller) or as prevalent in both orchard types (tarnished plant bug). Annual fruit damage in the insecticide-free orchard was mostly from the apple maggot (up to 98%), the plum curculio (up to 90%) and the codling moth (up to 58%). The average situation was different in commercial orchards, whose damage was mostly from the plum curculio (up to 7.6%), the tarnished plant bug (up to 7.5%) and the oblique-banded leafroller (up to 1.7%). While the number of registered pesticides, the number of applications and the total cost of pesticides gradually increased from 2002 to 2019, the risks incurred, as measured by indicators of environmental and health impacts, followed a downward trend for insecticides and acaricides and varied slightly for fungicides.

Exclusion netting systems are effective in various contexts and are increasingly used to control crop pests. However, factors affecting pollination management under nets are poorly known. The pollination effectiveness of commercial bumble bee hives ofBombus impatiensCresson (Hymenoptera: Apidae) was studied for apple production under exclusion netting systems in a research orchard located in Quebec, Canada during 2016–2017. Sixteen single-row plots of apple trees (plot length: 18.5 m, cultivar GingerGold) were subjected to one of the following four treatments during bloom: (1) introduction of a bumble bee hive placed at the end of the row, under nets; (2) introduction of a bumble bee hive placed in the middle of the row, under nets; (3) negative control with no pollinators, under nets and (4) agronomic control with nearby bee hives (<50 m), without nets. Resulting post-harvest fruit quality (e.g., fruit weight, size, number and distribution of seeds) was evaluated, as well as correlations between bumble bee visitation rates and fruit quality parameters were evaluated. Results suggest that bumble bees provided adequate pollination under exclusion netting systems and that resulting fruit quality was equivalent to that of apple fruit conventionally pollinated by honey bees and wild bees community (bumble bees and other bees) in the orchard environment. Positioning bumble bee hives in the middle of the row provided better fruit load homogeneity in pollinated trees. Additional discussion on bumble bees as apple pollinators and on pollen distribution methods is also included.

Exclusion nets have been used successfully to protect fruit from insect pests of apples under various conditions, but the effect of each particular netting system on the plant itself has rarely been investigated. In this study, a complete exclusion system—in which the soil is also excluded—was used to grow ‘Honeycrisp’ apples for six years in southern Quebec, Canada. Abiotic conditions, as well as plant photosynthesis and fruit quality characteristics (colour, firmness, size, sugar content, number of seeds, ripeness and skin integrity) and yield were estimated yearly and compared in netted (either with or without a rainproof top) and unnetted row units. Although annual variations were high and results showed little or no difference between netted and unnetted rows for all measured variables, with the following exceptions; colour (increased red surface on fruits from unnetted rows some years), size (fruits from unnetted rows were smaller) and maturity (fruits from unnetted rows matured slightly faster). Fruits produced under nets had fewer microcracks at the surface than fruits produced without nets. Reduced cracking possibly helped decrease sooty blotch and flyspeck incidence and severity. Impacts for pest control and prospects for pesticide-free production are discussed.

La punaise marbrée, Halyomorpha halys (Heteroptera: Pentatomidae), a été dépistée dans le sud du Québec à travers un réseau de 137 pièges pyramidaux appâtés déployés en milieux urbains et ruraux entre 2014 et 2017. Au total, 73 adultes et 9 nymphes ont été capturés. La première capture en milieu rural (un verger de pommiers) et les premières captures en milieu urbain (à Montréal) ont été rapportées en 2016. La même année, 87 % des 54 individus (adultes) capturés à Montréal provenaient du même piège. Similairement en 2017, seulement deux adultes ont été capturés en milieu rural et 87 % des 25 captures (16 adultes et 9 larves) en milieu urbain ont été observées dans le même piège qu’en 2016. Ce piège a aussi été le seul dans lequel des larves de différents stades ont été capturées, suggérant un établissement de population à Montréal. Les spécimens de ce site (quatre adultes et deux larves), séquencés à cette fin, se sont révélés être de l’haplotype H1. Plus de 40 observations et interceptions par les citoyens entre 2008 et 2018 sont aussi rapportées.