Effect of introductions of a predator complex on spider mites and thrips in a tunnel and an open field of pesticide-free everbearer strawberry

Abstract

Abstract. BACKGROUND:Chemical control of spider mites and thrips in everbearer strawberry is difficult as few efficient chemicals are available and residues represent a risk. In the north the success of biocontrol of mites and thrips in open fields compared with tunnels needs to be evaluated. OBJECTIVES: To investigate the need for control of spider mites and thrips and evaluate the effectiveness of biological control agents in everbearer strawberry. METHODS: Similar experimental plots, in a tunnel and an open field, planted with three everbearer strawberry varieties were arranged to compare the effect of introductions of the spider mite predator Phytoseiulus persimilis and releases of the generalist predatory mites Neoseiulus cucumeris and Neoseiulus barkeri and a predatory bug, Orius majusculus. Several sampling methods were used to evaluate mite and thrips populations. RESULTS: Phytoseiulus persimilis was successful against spider mites. Naturally occurring cecidomyiid and staphylinid predators affected control positively. Thrips damage remained mostly tolerable. The dominant thrips species were Thrips major, Thrips atratus, Thrips vulgatissimus and Frankliniella intonsa. Thrips numbers in the beating tray samples correlated with thrips damage to berries. CONCLUSIONS: Predatory mites were effective in controlling spider mites in an open field and a tunnel. The need for thrips control depended on the strawberry variety. Naturally occurring predators contributed to the control of spider mites and thrips.

Species Composition of Thrips (Thysanoptera: Thripidae) in Strawberry High Tunnels in Denmark

“…The July peak of infestation is in accordance with other studies in temperate climates [ 19 , 53 , 63 , 69 ]. It is likely that remaining flowers in tunnels in mid-August maintained thrips numbers above those in May.…”

“…The identification of adult thrips sampled from tunnel-grown strawberries at three other strawberry farms supported these findings. Globally, only few studies have reported findings of F. intonsa in strawberry, and even fewer in high tunnel systems, of which only one in Scandinavia, which also reported F. intonsa to be a dominating species [ 53 ]. A high number of F. intonsa in greenhouse strawberry was recorded by Lim and Mainali [ 54 ] in Korea, in outdoor commercial fields by Mintu and Reyes [ 55 ] in the Philippines and by Atakan [ 56 ] in the Eastern Mediterranean area of Turkey.…”

“…The two species F. intonsa and T. tabaci co-occur in different crops, but in most cases F. intonsa is the most frequently found species of the two [ 53 , 56 , 59 , 60 , 61 ]. The third and fourth most common adult species found were T. fuscipennis and T. major , two species of thrips that are also quite common pests of strawberry [ 14 , 15 , 62 ] ( Figure 1 ).…”

“…Additional species sampled included T. atratus and T. vulgatissimus ( Figure 1 ), both commonly reported in tunnel-grown strawberry [ 21 , 53 , 63 , 64 ]. Finally, few individuals of L. cerealium and A. obscurus were sampled.…”

“…It is likely that remaining flowers in tunnels in mid-August maintained thrips numbers above those in May. The sharp decline in thrips numbers by the end of August was likely due to an observed decline in the number of flowers and larvae dropping to the ground to commence pupation [ 19 , 53 , 63 , 69 ]. The earlier flowering Murano had more thrips than Furore.…”