wiliwili allies, Pteromalidae wasps

 On our recent survey on April 11th, we discovered that some seeds were filled with tiny bugs whom appeared dead when the seeds were cut open.  These were actually cocoons of Pteromalidae wasp, as identified by  Ross Hill contributor to http://www.bugguide.net,  a parasitic wasp that preys on the larvae of Bruchid  beetles that infect the seeds.

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wiliwili tree pests

 

Bruchid beetles (Specularis impressithorax) emerged from wiliwili seeds collected in September 2008. These seeds were stored in a glass jar for six months. the beetles lay dormant inside the seed and eat their way out through little hatches. One seed was infested with six beetles. Finding them emerged after a six months hibernation was a surprise. I  selected only seeds that were free from any penetrations, some were just pin pricks, but apparently these parasites were already inside. This bit of news is disturbing for all the seeds that were collected in the effort to save the wiliwili trees unless precautions were made to kill the beetles prior to storing them in one location.  After two hours in the freezer, these beetles came back to life as soon as they were exposed to room temperature.     According to the link http://www.hear.org/species/erythrina_sandwicensis/pdfs/wiliwiliseedform.pdf using water to test whether a seed float to determine that it is infected, is not fool proof. I discovered a seed that has tell tale signs of infection, a circular bump similar to a pimple on its skin where a beetle will exit. This seed sank to the bottom like other supposedly clean seeds, but when cut open, I found a dead beetle below the bump. Freezing the seed and everything else with it may kill the beetle but not its eggs. I supposed I will have to find out by experiment.

wiliwili tree seeds and seedling

I collected more seeds from a group of wiliwili trees just outside of Kamuela ,Hawaii in the shadow of Pu’u Huluhulu. Wiliwili seeds resemble kidney beans. My intent is to propagate these plants by starting them from seeds. Seeds are collected as the drop to the ground. The soil underneath these trees are dry and free of any germination from seedlings. I scouted at each visit but fail to see any starters. There are still seeds in pods on the branches so hopefully there will be more seeds to be collected. This stand of trees appear healthy.

Most seeds are damaged by parasitic wasp as evident by small pin hole(s). Others and i have tried to germinate the damage seeds without success. Inert seeds are dark brown or maroon while live ones are red or orange. Damages occur while seeds are still on the branches.

I did have a successful germination by simply inserting the seed in dirt and keeping the soil moist. the seed sprouted in about one week.

Wiliwili trees are endemic Hawaii plants and are threatened.