MSU Extension Floriculture & Greenhouse Crop Production

Starting and staying clean(er)

Prevention and sanitation are critical in reducing the risk of insect and disease outbreaks in the greenhouse. Incoming plant material, even if it appears uninfested, is one of the most common ways that insect and mite pests are introduced into floriculture production facilities. Ideally, growers should place all incoming plugs and liners into a quarantine area where they can be regularly monitored and, if necessary, treated for an infestation before moving them into the production area. Operations that maintain stock plants for cuttings should strive to keep insect and mite numbers on the stock plants as low as possible. Stock plants often develop a thick canopy, which can reduce the penetration and efficacy of spray applications. In such cases, an integrated approach using beneficial organisms could prove to be the most effective and resource-efficient option over time.

Scouting is important

Managing a small population of pests is much easier than managing a large one. Regular scouting/monitoring can help growers detect infestations early and prevent damaging outbreaks. The two most useful tools for scouting are the yellow sticky card and the hand lens. Sticky cards provide a snapshot of all the flying/jumping insects in the crop and are the ideal tool for monitoring thrips populations. Place one card at canopy level every 2000-4000 ft2 or at least one per house. Physical inspections of foliage and flowers are required to detect non-flying pests such as aphids and mites. A hand lens is used to examine tiny insects and mites and can help confirm pest identification.

Neonicotinoids

Neonicotinoids are class of insecticides that grew in popularity due to their relatively low mammalian toxicity and ability to move systemically throughout the plant. All neonicotinoid products are in the Mode of Action (MoA) group 4A (see below). Growers with buyers that require neonicotinoid-free plants should look to systemic insecticides in other chemical classes or MoA groups, such as Altus (group 4D), Mainspring (group 28), and Kontos (group 23).

Pyrethroids

Pyrethroids are a class of insecticides with a molecular structure similar to pyrethrins, which are natural compounds produced by some Chrysanthemum species. Like neonicotinoids, pyrethroids are used extensively throughout the world because of their broad-spectrum insecticidal activity and negligible toxicity to humans and other mammals. Due to documented resistance issues in all major greenhouse floriculture pest groups and incompatibility with many biological control agents, we no longer recommend pyrethroids as a primary insect management tool. They still, however, provide some usefulness in rotation or in a tank-mix with other insecticide products. All pyrethroids and pyrethrin products are in the Mode of Action Group 3A (see below).

Resistance Management

Repeated use of products with the same MoA over an extended period of time will create pest populations that are less susceptible to those products (see pyrethroids). To delay or prevent pesticide resistance, growers should develop a rotation schedule of products with a minimum of 3 different Mode of Action (MoA) groups (more is better). Mode of Action classification of products are published by the Insecticide Resistance Action Committee (IRAC) with the goal of prolonging the effectiveness of insecticides and miticides.

More information on IRAC and Mode of Action: https://irac-online.org/mode-of-action/ 

Phytotoxicity

Manufacturers typically test their products on a broad range of plants. They cannot, however, test a product for compatibility with every ornamental species and variety.

Before applying a product to a crop for the first time, you should:

• Consult the label for crop tolerance considerations.
• Test the product at the desired rate on a small number of plants.

If mixing the product with adjuvants or other products for the first time, you should:

• Consult for label for tank-mix compatibility notes.
• Test the product at the desired rate on a small number of plants.

Insecticide products for key greenhouse pests: 

MoA = Mode of Action

REI = Restricted Entry Interval

UNM = Non-specific mechanical and physical disruptors

¹ Other azadirachtin products include: AzaGuard, Azatrol, AzaSol, Ornazin

² In research trials, foliar spray applications of Safari, Flagship, and Kontos were as effective as drenches at controlling mealybugs. Adding a spreader adjuvant such as Capsil or Silwet resulted in improved efficacy.

** Restricted entry intervals vary across azadirachtin products. Please consult the label.

MSU is an affirmative-action, equal-opportunity employer. Michigan State University Extension programs and materials are open to all without regard to race, color, national origin, gender, gender identity, religion, age, height, weight, disability, political beliefs, sexual orientation, marital status, family status or veteran status.

We thank JC Chong of Clemson University for his review of this document.

The information presented here is for educational purposes only. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned.