Insect netting: effect of mesh size and shape on exclusion of some fruit pests and natural enemies under laboratory and orchard conditions

Abstract

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.

Hail netting excludes key insect pests and protects from fruit damage in a commercial Minnesota apple orchard

“…It has been observed in previous studies that there is potential for outbreaks of secondary pests such as the European red mite, aphids, and leafrollers under netting systems ( Marshall and Beers 2021 , 2022 , Chouinard et al 2022 ). While we did not observe any secondary pest infestations in this study, or any fruit damage or physiological symptoms of such pests under the netting, additional investigation into colonization under hail netting in Minnesota is needed.…”

“…In North America, there have been several studies documenting the effectiveness of different types of exclusion netting for insect pests in apple ( Chouinard et al 2016 ). In Quebec, Canada, a 5-yr study documented the effectiveness of a single row, complete exclusion netting system (1.9 × 0.95 mm mesh) that prevented damage from the apple maggot, codling moth, and the tarnished plant bug ( Lygus lineolaris Palisot de Beauvois, Hemiptera: Miridae) ( Chouinard et al 2017 , 2022 ). More recently, a study in Washington found that codling moth could be excluded by using net cages (2 × 5 mm mesh) placed around large orchard blocks ( Marshall and Beers 2021 , 2022 ).…”

“…Additionally, the investigators found that while the cages effectively excluded large, flying insects, smaller and less mobile insects such as aphids were consistently more abundant inside cages than outside ( Marshall and Beers 2021 , 2022 ). Leafrollers, such as the oblique-banded ( Choristoneura rosaceana Harris; Lepidoptera: Tortricidae), can also establish higher population numbers under netting ( Chouinard et al 2022 ). Both the apple maggot and codling moth are able to move through mesh sizes that are similar to those employed in hail netting (variable mesh size: 7.4 × 3 mm, 6 × 1.8 mm, etc.)…”

“…Both the apple maggot and codling moth are able to move through mesh sizes that are similar to those employed in hail netting (variable mesh size: 7.4 × 3 mm, 6 × 1.8 mm, etc.) ( Sauphanor et al 2012 , Chouinard et al 2022 , Marshall and Beers 2023 ). It is believed that effective exclusion is due to both small mesh sizes and interference with mate-seeking behavior in the codling moth ( Tasin et al 2008 , Marshall and Beers 2023 ).…”

Sublethal effects of nine insecticides on Drosophila suzukii and its major pupal parasitoid Trichopria drosophilae

“…23,24 Recently Tait et al deeply reviewed the current knowledge on the D. suzukii control strategies highlighting future perspectives for a more sustainable and eco-friendly integrated pest management (IPM), 25 through the implementation of cultural, physical, genetic techniques and behavioral manipulation. [26][27][28] However, biological control has been considered as the most promising approach to manage D. suzukii and several methods have been set up, 29,30 including the intentional importation of the Asian Ganaspis brasiliensis Ihering (Hymenoptera: Figitidae), which is the best candidate for the classical biological control program among a panel of several co-evolved larval parasitoids. [31][32][33][34] However, the success of a classical biological control program requires the fulfillment of social, political and economic matters, as well as multiple field evaluations over the year.…”