Friday, 12 August 2016

This Week At the Farm - Red Clover Casebearer Monitoring

By Laura
The red clover casebearer (Fig. 1) is a small, metallic green moth belonging to the Family Coleophoridae.  The larval stage of the red clover casebearer (Coleophora deauratella) feeds on the contents of clover florettes and eventually the developing seed.  Three species of Coleophora have established in Canada; C. deauratella utilizes red and alsike clover, C. mayrella utilizes red and alsike clover, and C. trifolii utilizes sweet clover. All three species create cases from the floral or seed pod structures of the host plant they utilize.  The larval stage constructs the “case” from its host plant which is worn and carried much like a snail in its shell, hence the common name of “casebearer”.  In the fall, the red clover casebearer moves from floral structures it feeds upon to the ground, carrying its case.  When conditions prompt overwintering, the red clover casebearer retreats within its case and seals the opening with silk.  In the spring, the red clover casebearer can emerge and move in order to find suitable spring conditions.  The larva then pupates within its case and is observed to begin to fly by mid-June in the Peace River region, typically flying over a 6-8 week period.  The metallic, green micro-leps seek their host plant, feeding upon nectar and they lay their eggs on the host plant.  
Figure 1. Red clover casebearer (Coleophora deauratella) larva and adult. The larva creates a case which it wears until it becomes an adult. Image sources:

The IPM lab monitors red clover casebearers throughout the Peace Region. Pheromone traps and sweep-net collections help us monitor the moth flight period, the presence of mature larvae and densities in commercial fields of clovers.  The pheromone traps consist of a commercially available green unitrap, a pheromone lure (Otani, Mori, Evenden) as bait for the males and enclose a Vapona strip to kill and retain the specimens for later identification and counting (Fig. 2).
Figure 2. Green unitraps mounted singly on posts at the edge of a field are used for pheromone trap monitoring of male clover casebearer moths.
In the span of one week some traps can catch over 1000 casebearers! The casebearers are retrieved then later counted by summer students (Fig. 3) who wear gloves and dust masks to protect against the insecticidal vapona strip and inhalation of the tiny scales of the moths which coat the inside of the traps like dust.
Figure 3. Summer students count and record the number of casebearers collected from each pheromone trap. This trap had 1793 casebearer moths.

For more information on red clover casebearers in the Peace River region, visit$department/deptdocs.nsf/all/prm4587