Warmer, sunny weather, while generally welcome because of heating reductions and crop development benefits, is bringing on insect populations. Thrips problems continue to be observed in greenhouses. Damaging populations were observed this week on geranium, Vinca vine, peppers and Verbena. Thrips presence was confirmed by visual observation of crops, monitoring with sticky cards, and thrips injury symptoms on plants. Regular monitoring is needed to insure the success of thrips control in the greenhouse. Use sticky cards to monitor for adult thrips and check the cards weekly.
Of note is the fact that in greenhouses where biological control through the use of sachets of Neoseiulus cucumeris has been established, thrips numbers are virtually non-existent. This emphasizes the importance of deploying biological control approaches as early in the crop cycle as possible, and the benefits that can be realized in managing difficult and potentially damaging pests such as thrips. Biological control of thrips should be started early before populations increase. Commercially available biological control agents include: entomopathogenic nematodes (Steirnernema feltiae), predatory bugs (Orius species) and predatory mites, Neoseilus cucumeris, (Stratiolaepsis scimitus formerly Hypoaspis miles, and Amblyseius swirskii). Consult your biocontrol agent supplier for more information.
Some of the insecticides available for control of thrips include Aria, BotaniGard, Pylon, Mainspring Overture, Mesurol, and Pedestal. Insecticides with contact or translaminar activity are more effective. Make sure to rotate between different classes to prevent resistance development.
Aphids were also detected this week on Portulaca inhanging baskets. This detection illustrates the importance of regular monitoring for hanging baskets. A consistent weekly scouting program is needed to detect aphids early before populations explode. Regular random plant inspections of susceptible crops and cultivars is also critical to detect the wingless aphid nymphs. Look on the undersides of leaves and buds of aphid-susceptible crops. Biological control of aphids by the use of parasitoids is very effective in managing aphid population in the greenhouse. The most commonly used parasitoids are Aphidius colemani, and Aphidius ervi. Aphidius colemani is a tiny wasp that is effective against green peach aphids and melon aphids. The mechanism of control centers on the adult wasp that lays one egg inside an aphid. This egg hatches into a larva that feeds inside the aphid. When mature, a new adult wasp will emerge from the golden-brown aphid mummy. Aphidius ervi attacks larger aphids such as the foxglove and potato aphids. It resembles A. colemani but is about twice as large and darker in color.
Some of the insecticides available for control of aphids include Altus, Aria, BotaniGard, Distance, Endeaver, Enstar, Mainspring and Rycar. Make sure to rotate between different insecticide classes to prevent resistance development.
For more information, refer to:
Are You Ready for Thrips by Sinclair Adam: http://www.e-gro.org/pdf/2018_725.pdf
Come to Grips with Thrips by Dan Gilrein: http://www.e-gro.org/pdf/2016_528.pdf
Managing Aphids in Hanging Baskets by Dan Gilrein: http://www.e-gro.org/pdf/2016_511.pdf
- Jason Lanier and Geoffrey Njue, UMass Extension Greenhouse Crops & Floriculture Program with Jim Mussoni, Private IPM Scout