Monday, 30 May 2016

Diamondback moth monitoring

The host plants of the diamondback moth (Figure 1) belong to the family Brassicaceae, which includes canola, mustard, and broccoli. They lay their eggs on these plants, and these hatch to be small miners, which live inside the leaves. Older larvae are yellow-green caterpillars, which eat the leaves, flowers, and other tissues of the plant. The larvae finally pupate in cocoons on these plants and emerge as moths.  Each year, Diamondback moths travel north into Canada using high altitude air masses.  Moths travel from Mexico, southern United States and the Pacific northwest from April and on through the growing season.
Figure 1. Diamondback moth adult, larva and pupa (Wikimedia Commons, Government of Manitoba).  Note the two prolegs at the rear of the larva that form characteristic "spurs".

The IPM team monitors diamondback moths throughout the Peace River region with the goal of determining the timing and magnitude of the moths’ mass migration. To do this, we set up delta traps (Figure 2). These traps are lined with sticky cards and baited with the alluring scent of female pheromones to attract male diamondback moths. We align the traps east-west to funnel the prevailing winds. The traps are generally set out in late April and the sticky cards are collected weekly for 6 weeks or longer, depending on the timing of the moths’ arrival. Later in the season, once the crops have grown, we also count the number of diamondback larvae present on the plants per unit area by doing a beat sample. For more information about the life cycle and monitoring of the diamondback moth, check out our monitoring protocols.  

Figure 2. Delta trap used to capture diamondback moth moths in situ.  The pheromone lure is hung inside the trap and moths are collected on the sticky card inserted on the inner surface of the trap.

Back at the lab, we count the number of moths on each card (Figure 3). Working with the cards can be challenging, as the sticky substance will cover the lab tables, the instruments, and students’ fingers if these items are not protected. We also record the results of the beat sample and amalgamate all the data. The location of the site and the timing of each collection, along with the economic threshold for each crop, provide information about when crops should be sprayed with pesticides.

Figure 3.  Sticky card with diamondback moths marked using a blue dot.  By-catch insects include flies and beetles.
- Laura