Mating Disruption of Diamondback moth – An effective strategy that could reduce insecticide applications on cabbage and broccoli

Posted on by

Authors: Taylore Sydnor (Ph.D. Student), Alejandro Del-Pozo (Assistant Professor) & Thomas Kuhar (Professor) – Department of Entomology, Virginia Tech

Diamondback moth

Diamondback moth (DBM), Plutella xylostella, is an important pest of brassica crops worldwide including Virginia (Fig. 1). Management of this pest is challenging due to its ability to quickly develop resistance to insecticides. Therefore, integrated pest management (IPM) tactics are strongly desired. Mating disruption has been developed for DBM as an alternative to insecticides.  Mating disruption involves releasing high rates of the mating pheromone into fields confusing and/or desensitizing male moths so that they cannot find female moths and mate and produce damaging larvae on the crops.  The strategy has worked extremely well for tree fruit moth pests, and is currently being researched by our lab in Virginia for DBM. 

Fig. 1. Diamondback moth larva and leaf feeding damage.

Mating Disruption Trials

In the past three years we have tested several mating disruption dispensers and other products in commercial cabbage and broccoli fields in Hillsville and Mechanicsville, Virginia.  Similar research has been conducted in North Carolina and South Carolina by our entomology colleagues.  Virtually all of our trials have resulted in sentinel trap shut down of DBM moth catch in the middles of commercial brassica fields that have had mating disruption pheromones released (via dispensers) as compared with non-mating disruption (control) fields that had significant moth catch in the fields (Fig. 2).  When male moths cannot find females, then there will be little to no DBM larval infestations on the crops.  The Trécé Incorporated dispensers (Fig. 3) used in the aforementioned research are not commercially available yet. 

Fig. 2. Weekly catch of diamondback moths (mean ± SE) in baited sticky traps placed in the centers cabbage fields treated with mating disruption dispensers (n= 6) vs. control
Fig. 3. Trécé Incorporated MESO pheromone dispenser in a cabbage field. Photo credit: Taylore Sydnor.

Although we have tested various dispensers, tablets, and sprayable pheromones, with each demonstrating success for reducing DBM, the only commercial DBM mating disruption product currently available to growers is a sprayable pheromone, Checkmate® DBM-F (Fig. 4). The sprayable product has been around for a while, but not heavily used by commercial growers probably because of the plethora of effective lepidopteran insecticides that have hit the market in the past 25 years.  However, with DBM populations developing resistance to virtually all of the insecticide classes, mating disruption is now a more attractive option for managing this difficult pest. 

Fig. 4. CheckMate DBM-F mating disruption product from Suterra.

In 2024, we tested Checkmate® DBM-F in commercial cabbage in Hillsville, VA (4 treated fields paired with 4 control fields), then later in the fall in 2024 in broccoli in Mechanicsville, VA (1 treated field and 1 control field). 

Fields were sampled from July to August. Growers were encouraged to maintain their spray regimens to maintain homogeneity between field plots. All treatment fields in both locations were treated with Checkmate at a rate of 2 fl oz/acre approximately every 30 days. Three pheromone-baited delta sticky traps were placed equidistant in each field plot to monitor the DBM moth activity and were checked weekly. In Hillsville, we found that Checkmate® DBM-F was not significant in reducing DBM populations when compared to the control fields.  However, during this trial there was a lot of rain, 5.34” over a two-week span, that likely reduced the efficacy of the sprayable pheromone to last in the field. In fairness, the company does recommend re-applying the product after rain events.  See the following blog from Suterra that addresses the different rates and frequencies: https://www.suterra.com/blog/checkmate-dbm-f-flexible-spray-timings-for-diamondback-moth-control

This was not possible given the amount of rain that occurred during that 2-week stretch. We felt a more fair assessment of the product occurred with our test in Mechanicsville, where we found that DBM adult captures were significantly shut down in fields treated with Checkmate® DBM-F when compared to control plots (Fig. 5). Overall, we conclude that Checkmate® DBM-F has the potential to be effective in reducing DBM pest populations when applied at the proper conditions.  Growers need to be mindful of rainfall after application. 

Fig. 5. Weekly catch of diamondback moths (mean ± SE) in baited sticky traps placed in the center of broccoli fields treated with CheckMate DBM-F vs. control.
 

Over the past three years, we have tested several types of mating disruption dispensers and products for DBM, and have consistently achieved sentinel trap shut-down (= effective control) of the pest in cabbage and broccoli fields in Virginia.  We encourage growers to try this innovative strategy for controlling this very difficult pest. Please feel free to contact us if you are interested in trying mating disruption for DBM in Virginia.