Tips On Managing Onion Thrips

Onion thrips are a major onion pest and feeding damage can cause yield reductions of 30% to 50%. In addition, onion thrips transmit iris yellow spot virus, and the damage caused by their feeding can enable secondary pathogens to infect the crop.

Insecticides manage onion thrips and are very effective at reducing populations. However, past lessons with pyrethroid resistance highlight the importance of using these products only when necessary, and rotating different chemistries to delay development of insecticide resistance in these populations.

Thrips transmitted iris yellow spot virus  severely damaged the onion plants in this field. Photos credit: Brian Nault
Thrips transmitted iris yellow spot virus
severely damaged the onion plants in this field.
Photos credit: Brian Nault.

An insecticide resistance management (IRM) plan developed at Cornell University outlines which insecticides to use, and how many times to apply an active ingredient before switching to another that belongs to a unique class of chemistry. The goal is to expose each generation of thrips that develops over the growing season to a single active ingredient so that resistant individuals don’t continue to cause damage and produce resistant offspring.

Determine Scale For IRM Plan
While insecticide rotation is a very effective way to delay insecticide resistance, there are several factors that could interfere with the effectiveness of this strategy for onion thrips. The first has to do with determining the scale at which you’ll need to conduct your IRM plans.

To ensure that resistant offspring don’t persist, the IRM plan must be implemented at a scale that corresponds to the area inhabited by a population of onion thrips (i.e. according to how far onion thrips travel to reproduce). The second has to do with characteristics of the onion thrips populations themselves.

Spatial Considerations
Rotating insecticides from different classes is an effective way of delaying insecticide resistance from developing in pest populations. However, problems with this strategy occur when there is non-compliance or uncoordinated efforts by growers occurring in areas inhabited by the same insect population. As an example of non-compliance, think of two onion fields, A and B, planted next to each other but managed by different growers.

Grower A implements a chemical rotation IRM strategy, whereas grower B always sprays the same insecticide. In time, grower B will end up selecting for insects that are resistant to the insecticide being used, and will suffer crop losses. In addition, it is likely that resistant insects from field B will end up in field A because the distance between the fields is small enough that insects can move between them. As a result, grower A might suffer crop damage because of neighbor B not implementing an IRM strategy.

Five Tips To Manage Insecticide Resistance

  1. Manage pests without insecticides whenever possible by planting insect-tolerant cultivars, rotating fields, etc.
  2. Maximize efficacy of insecticides by applying them properly to the crop and targeting the most susceptible life stage.
  3. Limit the number of insecticide applications, for example, no more than two applications of the same product per crop per season.
  4. Rotate insecticide classes by using  products consecutively in a sequence to minimize exposure to multiple pest generations.
  5. Use action thresholds to determine when to spray the insecticide.

Coordinate Timing Of Sprays
In the example of uncoordinated efforts, where farmer A and B would both be implementing insecticide rotation strategies, insecticide resistance problems occur when timing of insecticide sprays and/or sequence of insecticide rotations is different.

Onion thrips are small and hard to observe, and little is known about their dispersal abilities.
Onion thrips are small and hard to observe, and little is known about their dispersal abilities.

If the insecticide rotation sequence is the same, but timing of insecticide applications is different,  this creates a lag where there is more time for resistant individuals to survive in the fields before they are killed by the next chemical class applied. Similarly, if the timing is coordinated, but the chemical rotation strategies differ, and grower A sprays the same chemical class grower B just finished spraying, then this allows
more opportunity for resistant individuals to survive, reproduce, and damage the crop.

Although these examples are between neighboring fields, these scenarios could play out over longer distances, the limits of which are as large as the dispersal capabilities of the insects. This means that farmer A and B only have to coordinate their efforts if thrips are actively moving between their fields.

Unfortunately, thrips are small and hard to observe, and therefore, little is known about their dispersal abilities. In addition, we know thrips can disperse long distances on wind currents; however, we don’t know how far they travel or how often this occurs.

Use Genetic Tools
One way to investigate movement of thrips without directly monitoring them is to use genetic tests to determine whether thrips from different mucks are related to each other. This information can then be used to determine whether IRM plans targeted against onion thrips in specific states need to be coordinated at local or regional scales.

If there are different strains of onion thrips, this means they need to be examined separately with regard to IRM because they could differ in characteristics related to insecticide resistance. However, if onion thrips strains are similar, then how far individuals travel to reproduce will be important.

Until recently, researchers at Cornell did not have genetic tests available to look at population-level associations among onion thrips. Now they can determine whether there are different populations or different strains of thrips to ensure they have the information about thrips they need to develop effective, long-term management strategies.

Current research underway at Cornell includes using a combination of tests that detect ancestral and population-level genetic differences, and they are currently in the process of examining the genetic relationships of onion thrips collected from onion mucks across New York.

By doing this, researchers hope to better understand if thrips populations are isolated in different mucks, or if they disperse to surrounding areas, and if so, how far they travel. The information will be used to help develop IRM plans that will be more effective at delaying the development of insecticide resistance and increase the longevity of the few effective chemical options that exist for onion thrips control in onion.

Editor’s Note: Alana Jacobson (aljacob2@ncsu.edu), and George Kennedy, (gkennedy@ncsu.edu), both in the Department of Entomology at North Carolina State University, also contributed to this article.

Topics:

Leave a Reply

Insect Control Stories
FruitsStink Bug Predator Found In U.S.
March 18, 2015
Wasp native to Asia attacks brown marmorated stink bug eggs. Read More
recently harvested avocadoes
Disease ControlUAVs, Dogs Called In To Battle Deadly Avocado Fungus 
March 18, 2015
Florida International University researchers team modern technology with man’s best friend to hunt down and detect laurel wilt disease. Read More
FruitsBe On High Alert For Leaffooted Bug
March 18, 2015
Now is the time to start scouting for leaffooted bug in almond orchards. Read More
Biocontrols 2015 Conference
CitrusGrowers Go In-Depth At Biocontrols 2015 Conference & Tradeshow
March 9, 2015
The first-of-its-kind event brought growers, researchers, regulators, and suppliers together for a two-day discussion on the latest biocontrols tools and technologies. Read More
Apples & PearsGet Ready For Brown Marmorated Stink Bug In 2015
February 23, 2015
No one can predict the future of this relatively recent invader, which is now found in 41 states, but all signs point to continued expansion. Read More
Crop ProtectionAt Paramount Farming, Mating Disruption Pays Off
February 10, 2015
To say Brad Higbee is an expert in mating disruption, the use of pheromones to confuse target pests and reduce Read More
Crop ProtectionGrower Experienced In Biocontrols Says: Be Patient
February 4, 2015
The use of biocontrols in all aspects of agriculture is becoming more widespread. But incorporating biocontrols in a vegetable farming Read More
The Latest
FruitsRare Leafhopper Found In Shipment At Delaware Port
March 24, 2015
This is the second time this pest has been discovered by U.S. Customs and Border Protection agriculture specialists. Read More
FruitsTips For Pear Psylla Management
March 24, 2015
Dormant oil applications should start as growers begin to experience warmer, mild weather. Read More
brown marmorated stink bug dog search team
FruitsUSDA Uses Man’s Best Friend To Track Stink Bug
March 23, 2015
It's all paws on deck to find brown marmorated stink bug's overwintering sites. Read More
FruitsStink Bug Predator Found In U.S.
March 18, 2015
Wasp native to Asia attacks brown marmorated stink bug eggs. Read More
recently harvested avocadoes
Disease ControlUAVs, Dogs Called In To Battle Deadly Avocado Fungus 
March 18, 2015
Florida International University researchers team modern technology with man’s best friend to hunt down and detect laurel wilt disease. Read More
FruitsBe On High Alert For Leaffooted Bug
March 18, 2015
Now is the time to start scouting for leaffooted bug in almond orchards. Read More
Apples & PearsGet Ready For Brown Marmorated Stink Bug In 2015
February 23, 2015
No one can predict the future of this relatively recent invader, which is now found in 41 states, but all signs point to continued expansion. Read More
Insect ControlEPA Announces Voluntary Cancellation Of Certain Methomy…
February 3, 2015
Some uses will be canceled and uses will be limited on certain crops to reduce drinking water risks. Read More
CitrusAsian Citrus Psyllid Marches North In California Citrus…
January 22, 2015
Part of one of the richest agricultural areas in the U.S., Fresno County, has been quarantined. Read More
Insect ControlExceptional Care Needed When Taking On Common Blossom T…
January 21, 2015
Learn how to identify, the survival and spread, as well as management methods for this insect pest of vegetables. Read More
CitrusBayer CropScience Launches Latest Insecticide, Sivanto
January 20, 2015
New product delivers precision pest control to preserve the health of plants and protect fruit and vegetable crops. Read More
CucurbitsNew Product Takes Aim At Nematodes
December 19, 2014
NIMITZ receives EPA and Florida registrations. Read More
FruitsGrower Input Needed For Spotted Wing Drosophila Survey
December 16, 2014
Results of stakeholder needs survey helps prioritize research and education activities. Read More
FruitsSumitomo Chemical Acquires U.S. DuPont Asana Insecticid…
December 9, 2014
The insect control product will be distributed through Valent U.S.A. Read More
Insect ControlPrepare For The Bagrada Bug
December 5, 2014
Find out how to identify this pest that is plaguing growers in the West, and how you can control it. Read More
Insect Control6 Pests Of Snap Beans To Watch For In 2015
December 4, 2014
Two researchers in the East discuss which pests cause the most damage and how to keep them from taking over your crop. Read More
BerriesSpotted Wing Drosophila Regional Workshops Held In New …
December 1, 2014
Management tips, early warning signs, and pest biology are among topics discussed at one-day events. Read More
Apples & PearsEPA Approves Three New Moth Mating Disruption Products
November 25, 2014
Codling moth and oriental fruit moth are targeted by apple and pear growers. Read More