Field-testing the sex pheromone of cranberry tipworm, Dasineura oxycoccana (Diptera: Cecidomyiidae) ● Sheila M. Fitzpatrick ● Miranda Elsby ● Kaitlyn Schurmann ● Snehlata Mathur Pacific Agri-Food Research Centre, Agassiz, BC, Canada

Female cranberry tipworms produce and release sex pheromone. The sex pheromone is volatile and airborne. Males detect pheromone molecules and fly toward females. Landry

The sex pheromone was identified by Regine Gries, Grigori Khaskin and Gerhard Gries at Simon Fraser University. “Populations of the gall midge Dasineura oxycoccana on cranberry and blueberry produce and respond to different pheromones” by S. Fitzpatrick, R. Gries, G. Khaskin, D. Peach, J. Iwanski, G. Gries in Journal of Chemical Ecology 39(1): 37-49; 2013. The sex pheromone is a potential monitoring tool for cranberry tipworm. Here I report the outcome of field tests of the sex pheromone on cranberry farms in British Columbia, Canada. Funded by AAFC (DIAP partnership with LMHIA), BCCMC, BCCGA and Investment Agriculture Foundation.

Chemistry of Cranberry Tipworm Pheromone The parent molecule is a straight-chain 17-carbon alkene with two functional groups. OAc C C C C C C C C C C C C C C C C C OAc The molecule is named 2, 14-diacetoxy-8-heptadecene. This racemic molecule is a mixture of 4 optical isomers.

Only one optical isomer is Cranberry Tipworm Pheromone OAc (R) C C C C C C C C C C C C C C C C C (R) OAc OAc (S) C C C C C C C C C C C C C C C C C (R) OAc OAc (R) C C C C C C C C C C C C C C C C C (S) OAc OAc (S) C C C C C C C C C C C C C C C C C (S) OAc

CTW pheromone was tested on two farms in 2012. Traps were baited with the isomer (S,S)-2,14-diacetoxy-8-heptadecene, or racemic pheromone or a blank lure. Male cranberry tipworm J.-F. Landry photo

Tipworm males in traps baited with single isomer CTW pheromone Average number Dotted lines show Delegate sprays

caught in traps baited with CTW pheromone … … was a good predictor of Tipworm males caught in traps baited with CTW pheromone Tipworm males caught in traps baited with CTW pheromone Average number Average number On this farm, the number of CTW males caught in traps baited with CTW pheromone … … was a good predictor of the percent of shoot tips infested with CTW eggs, larvae or pupae. Shoot tips infested with eggs, larvae or pupae Average Percent

… the first major increase in immatures (week 8). Increased trap catch on July 11 corresponded to … … the first major increase in immatures (week 8). Shoot tips infested with eggs, larvae or pupae Eggs First Instars Second Instars Third Instars Pupae Number per 10 shoot tips J.-F. Landry photos

The preceding graphs show that single isomer pheromone has potential to be an excellent monitoring tool. Unfortunately, synthesis of this single isomer (S,S)-2,14-diacetoxy-8-heptadecene is very expensive. Therefore, the single isomer pheromone will not be available commercially. The following graph shows the attractiveness of racemic 2,14-diacetoxy-8-heptadecane, which is less expensive to synthesize. Also shown is the attractiveness of traps to females.

Tipworm males caught in traps baited with single isomer or racemic pheromone Average number

Tipworm females were caught in all traps, regardless of bait. Average number

Racemic 2,14-diacetoxy-8-heptadecane is much less attractive than is the single isomer (S,S)-2,14-diacetoxy-8-heptadecene. Monitoring with racemic will not provide precise information about activity of cranberry tipworm adults. Female cranberry tipworms entered all traps without discriminating among baits. Therefore, in 2013 we tested the relationship between number of females caught in unbaited traps and percentage of shoots containing immatures (eggs, larvae, pupae).

On this farm (and all others), the number of females Tipworm females caught in unbaited white sticky traps Average number On this farm (and all others), the number of females caught in unbaited traps … … was a poor indicator of the percent of shoot tips infested with CTW eggs, larvae or pupae. % of shoots infested with eggs, larvae or pupae

General, somewhat disappointing, conclusions Cranberry tipworm sex pheromone is very attractive to tipworm males but is prohibitively expensive to synthesize and therefore is not available for use on farms. The number of female tipworms attracted to unbaited traps does not provide precise information about the percentage of shoots infested with immature tipworms. The most accurate way to detect cranberry tipworms is the method of collecting a sample of shoot tips then examining them under the microscope to count eggs, larvae and pupae.

An optimistic and encouraging observation The recently registered insecticide Movento (spirotetramat), applied AFTER BLOOM, is a very effective management tool. D M De M D live immatures dead live & dead × empty cocoons

2 graphs … females top; % infested shoots bottom Comment from poster … these results typical of 13 fields. Picture of trap?