Thrips management resource available

There are a number of thrips species that are capable of causing problems in ornamental production. To help growers combat this troublesome group, new educational tools have been developed.

Earlier this year a group of entomologists from around the country developed the “Thrips Management Program for Plants for Planting.” This document is unique in that besides providing basic IPM information, it has a dichotomous key for growers to help determine which insecticide(s) to use to manage western flower thrips, chilli thrips, gladiolus thrips, and Gynaikothrips. It’s available by clicking here.

The program does not require a pesticide application when the first thrips is detected. However, it does outline steps to manage and maintain thrips populations throughout the initial propagation and active growth stages at levels to enable complete control on final plant material being shipped. Growers should apply pesticides when scouting reports identify population densities at levels where experience and/or extension personnel dictate action be taken. These densities would depend on many factors including the crop, source(s) of infestation, history of viral infection and environmental conditions.

Western flower thrips vector impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV). Thrips can vector plant viruses in less than 30 minutes during feeding. Because of the potential to vector virus diseases, it is critical to practice good scouting, sanitation and exclusion wherever possible.

Sanitation
Remove weeds, old plant debris and growing medium from within and around the greenhouse. Eliminate old stock plants, which are a source of thrips and viruses. Removing old flowers may reduce the number of WFT adults and eggs. Place flowers into a sealed bag or container and dispose.

Biological Control
Several biological control agents are available for managing thrips, including predators (Neoseiulus or Amblyseius spp., Orius spp. and Hypoaspis mites), nematodes (Steinernema feltiae) and entomopathogenic fungi (Beauveria bassiana). The key to using biological control against WFT is to release natural enemies early. Releases must be initiated before thrips enter terminal or flower buds. Biological control agents will not control a large existing thrips population.

Chemical Control
No insecticide will provide complete control of thrips. It is important to detect and start management strategies before thrips populations have a chance to increase to moderate or high levels. Use the shortest labeled interval when pest pressure is high and temperatures are warm. Insecticides should be rotated by changing modes of action with each treatment or at most with each generation of thrips, unless the label indicates otherwise.

To help decide what chemical approach, if any, you should use, the dichotomous key will lead you to one of four groups.  These are:
 

• Plants are virus hosts and thrips are present.
• Plants are ready to be shipped and thrips populations are present in high enough numbers to downgrade the crop.
• Plants have a population of thrips that need to be managed but they aren’t virus hosts.
• Actions: Cull any plants expressing virus symptoms.
• Rotate among products of different IRAC classes in table below.
• If thrips population does not drop as expected after treatment, do not use that product for at least one thrips generation.

• Plants are virus hosts but they are without thrips.
• Plants are not virus hosts but have low populations.
• Actions: Same as Program A with applications only when thrips populations exceed threshold levels.
• If both virus symptoms and thrips are noticed during scouting, move to aggressive treatment program.
   

• Plants are virus hosts but they are without thrips.
• Plants are not virus hosts but have low populations.
• Actions: Same as Program B except using products which don’t impact biological control agents.

Program D - Maintenance Treatment Program (prior to biological control agent introduction)

• Plants are virus hosts but they are without thrips.
• Plants are not virus hosts but have low populations.
• Actions: Prepare for reintroducing biological controls into Maintenance Treatment Program.

Chilli thrips e-learning module
The National Plant Diagnostic Network (NPDN) recently released the chilli thrips e-learning module. The module is an interactive tool that will provide you with an introduction to the distribution, life history and pest status potential for chilli thrips, in the U.S.

Upon completing this module you will:

• Be familiar with the origin and current status of chilli thrips in the U.S.
• Be familiar with damage symptoms
• Understand the life cycle of chilli thrips
• Know general management options
• Be familiar with local resources for obtaining management recommendations
• Understand thrips sampling techniques
• Know how to submit a thrips sample to an appropriate diagnostic laboratory
• To view the chilli thrips e-learning module, go to http://cbc.at.ufl.edu/ and click on “take the online modules.” You must have an account set up with the National Plant Diagnostic Network to view this module along with others on the site. The chilli thrips e-learning module includes a post-test.

A certificate of completion for the module will be available for download once the module has been completed at the 70 percent level or higher.

The chilli thrips training module was developed by Amanda Hodges, Lance Osborne, Howard Beck (University of Florida/IFAS) and Scott Ludwig (Texas AgriLife Extension Service).