Help: Insects Eating My Hardy Hibiscus Seeds

This evening much to my dismay, I discovered that what appears to be a small beetle like insect has been eating my hardy Hibiscus seeds. The seeds which have been eaten have round holes in them and I have found the insect in side the seeds. I don’t know if the insect hatched inside seed or was able to cut through the outer shell. I had the seeds stored a shed which was quite cool but they were not in sealed containers.

Any ideas as to what is going on and how can I put a stop to it? Are there any chemicals I can use or is it too late to save the seeds?

Mike

I don't know too much about it, but I do remember someone else posting the same problem and it was weevils--here's the thread (and there's a link in it to another thread about the same thing) http://davesgarden.com/community/forums/t/913410/ I don't know if they came up with a good solution to the problem, but if you google weevils & hibiscus seeds you may find some more info.

Ecrane3,

Many thanks. The problem sounds exactly like mine. Some of the compromised seeds were like Mexican Jumping Beans with the weevils inside. Independently I did try freezing which appears to work but I don’t know what the impact is on the hardy Hibiscus seeds. I will now have to run some germination tests.

As suggested in the other post you linked to, I will purchase Ortho's "Home Defense Max" in the morning as I have other seeds which I did not freeze. I am also transferring the seeds to ZipLock bags to isolate any further infestation. It looks like the seeds may have been compromised in the pod as this Google search suggests which also found other posts in DG.

http://www.google.com/search?hl=en&source=hp&q=Hibiscus+seeds+weevils

I have purchased hardy Hibiscus seeds with identical holes in them so I am going to have to be very carful in the future. This would also explain the poor germination results I have obtained with seeds from some sources and not others. I would also like to identify the weevil and its life cycle. This paper sounds like it describes the problem accurately.

Temporal and Geographic Variation in Predispersal Seed Predation on Hibiscus moscheutos L. (Malvaceae) in Ohio and Maryland, USA
http://www.biosci.ohio-state.edu/~asnowlab/klipsbau.pdf

Two insects were identified:

The seed predators were a weevil, Conotrachelus fissinguis (Coleoptera, Curculionidae) and a bruchid beetle, Althaeus hibisci (Coleoptera, Bruchidae).

I will run some controlled tests to evaluate germination success and post the results here. I need to determine the impact of freezing and the weevil damage.

Update:

The spelling of Conotrachelus fissinguis used in the above paper is not the prevalent form used across the Internet. The more common spelling is Conotrachelus fissunguis where second “i” in the species name is replaced with a “u”. In taxonomy it is not uncommon to find variations in spelling depending on the source but there is also the possibility that an error exists in above paper. The following is a picture of C. fissunguis.

Conotrachelus fissunguis
http://bugguide.net/node/view/320813/bgimage

The weevil C. fissunguis larvae eats the seeds as they develop and then bores a hole through the pod and drops to the ground to continue development.

What I am observing is adult insects emerging from fully developed Hibiscus seed, therefore I am dealing with the Bruchid beetle Althaeus hibisci and not the weevil Conotrachelus fissunguis.

Bruchid beetles lay eggs on the immature capsule soon after the petals abscise. Shortly after hatching, their larvae burrow through the ovary wall and each enters an ovule, within which larval development and pupation take place. Infested seeds reach their full size and appear normal, but they are hollow and dead. Adult beetles emerge from the seeds during late autumn (after the fruit capsule has dehisced) through a 1 mm diameter hole in the hard seed coat.

In a related paper there is an indication that nonviable Hibiscus seeds don’t float. This may be a way to separate the good and bad Hibiscus seeds.

A GENETIC ANALYSIS OF HYDROLOGICALLY DISPERSED SEEDS OF HIBISCUS MOSCHEUTOS (MALVACEAE)
http://www.amjbot.org/cgi/reprint/88/4/588.pdf

Although high seed infestation rate by a bruchid seed beetle, Althaeus hibisci, has been reported in the study area (Kudoh and Whigham, 1998), nonviable seeds rapidly lose their buoyancy (R. Shimamura, Tokyo Metropolitan University, unpublished data).

I am still looking for a picture of Althaeus hibisci.

Mike


This message was edited Nov 13, 2009 9:01 PM

Mike

Forget freezing! After three hours in the freezer the weevils appeared to be dead until they warmed up and then it was business as usual. Next I try Ortho's "Home Defense Max".

Mike

Mike,
I've got the same problem with some hib seeds I got from across the street. I don't know if I've saved any of the seed, but will also try germination tests on the seeds. I was adviced to freeze the seeds for 2 weeks before planting, so I'm giving that a try. Keep us informed of how yours are doing.
Mary

I have a large number of wild Hibiscus moscheutos seeds which were collected in New Jersey about 10 miles from my home and which are infected with Althaeus hibisci. The seeds of my named Hibiscus cultivates in my garden are also infected by A. hibisci. The A. hibisci had done their dirty work back in August and the seeds were already lost back then but I didn’t know it as they appear absolutely normal on the outside. I suspect that many of the problems gardeners have germinating hardy Hibiscus seeds are the result of A. hibisci infestation. I already have seedlings growing from my wild H. moscheutos seeds but the yields were nothing like what I had expected, now I know why.

After I learned that a 3 hour visit to the freezer put the A. hibisci into a dormant state but did not kill them, I selected several hundred H. moscheutos seeds and hand cleaned them removing any seeds which had emergence holes or appeared damaged. I put them into a ZipLock bag for observation. Within 6 hours the bag was crawling with newly emerged A. hibisci and there were an equal number of dead Hibiscus seeds with holes in them. I purchased a 24Oz hand-spray bottle Ortho's "Home Defense Max" at Lowes for $4.98. I gave the contents of the bag one squirt of Ortho, which may have been too much, mixed the seeds, bugs and insecticide inside the bag and then dried the seeds on a paper towel to remove any excess insecticide which is water based. The active A. hibisci were dead within a few minutes of exposure to Ortho. I put the dried seeds back into the now cleaned bag and did not observe any new A. hibisci emerging from the seeds so I am assuming that any remaining beetles died inside the seeds. After the Ortho treatment, the seeds with holes in them became a lighter shade of brown. I am planning to run some tests with lower concentration of Ortho by diluting the Ortho with water before immersing the seeds. Blomma had also suggested the use of Malathion for the seeds and next summer which I am looking into.

Using a germination technique recommended by Blomma (http://davesgarden.com/community/forums/t/1047978/) I am going to determine of any the seeds are still viable after the Ortho treatment. As suggested in Blomma’s procedure I am first socking the seeds overnight in warm water. I have found that some of the seeds do sink but the floating seeds also include those seeds with holes in them. It may take time for the nonviable seeds to sink and will make the final evaluation before I move the seeds to the next step in the germination process. I plan to run germination tests on both the floaters and sinkers to see if there is really a difference in the germination rates.

Some of the Hibiscus seeds which are being used in this test are know to be viable. The adult A. hibisci are no danger to mature Hibiscus seeds as the damage was done months ago. The primary issue here is preventing the spread of A. hibisci through seed trading. A secondary issue is that A. hibisci predation can be over 95% in some documented cases. Some of my 11”x22” starter trays contain only a few seedlings when they could accommodate 96 seedlings. In situations where there is high seed predation because of A. hibisci Blomma’s technique will allow me to discard the nonviable seeds before planting which will save a lot of growing space.

The following Google search string will find any reference to Althaeus hibisci.
http://www.google.com/search?as_epq=Althaeus+hibisci&num=100

The adult A. hibisci beetle feeds on Hibiscus pollen and may also be a Hibiscus pollinator. Is A. hibisci relationship with Hibiscus parasitic or symbiotic? Having made that profound observation, how do I stop A. hibisci next July and August?

I will keep everyone posted on the germination and insecticide tests. If anyone finds a picture of Althaeus hibisci. please post it.

Mike

I have been unable to find an absolute lock on photograph identification for Althaeus hibisci but I did find four pictures for the Genus Althaeus and two of the photographs look exactly like beetles which are destroying my Hibiscus seeds. Take note of the commentary associated with the photographs and the plants on which the beetles were found.

Genus Althaeus
http://bugguide.net/node/view/248420

These are the photographs which look most like the beetles on my Hibiscus seeds.

Possible Photographs of Althaeus hibisci
http://bugguide.net/node/view/303072
http://bugguide.net/node/view/306279

Input from anyone with the same problem would be appreciated.

Mike

unbelievable...I haven't seen the problem in my seeds yet but sounds like it's on the east coast predominately. Appreciate the info, thanks for posting it.

Using the technique described by DG member Blomma, I initiated the process to force the germination of approximately 200 Hibiscus moscheutos seeds which were infected with Althaeus hibisci and treated with Ortho's "Home Defense Max". After some though I decided to not nick the wild Hibiscus moscheutos seeds, as Blomma recommended, because these seeds are significantly smaller than the seeds we collect from our named domestic cultivars or other wild species such as Hibiscus coccineus. When I first saw the seeds of wild H. moscheutos I thought that there was something wrong until I check the USDA database and verified that wild H. moscheutos seeds are significantly smaller than other Hibiscus. What is being sold in our garden centers is not H. moscheutos but hybrids of multiple Hibiscus species including H. coccineus and seventy-five plus years of selective breeding. Let’s be honest, do breeders select small seeds or large seeds to breed the next generation? Bigger is always better or is it? In any case, I was working with over 200 seeds in this test and nicking that many seeds of this size would have been no small task.

All of these seeds were treated with Ortho's "Home Defense Max" based on the recommendation in other DG posts; and, yes I have now purchased Malathion for the next round of tests but more on that later. When I put the 200 plus seeds into hand-hot water and the seeds which I suspected were compromised swelled to twice their normal size and began to sink. What appeared to be healthy H. moscheutos continued to float. The shells of the sinkers were soft and when I cut a few of them open I found what appears to be a very dead Althaeus hibisci inside each compromised seed. I am using the Verizon FiOS TV interface unit to keep the water bath slightly warm for a full 24 hours. Using a fish net I separated the floaters and the sinkers into two groups of about 100 seeds each and setup two of Blomma’s four-ply germination ZipLock bags. The two bags are now on a disposable aluminum baking tray on top of my FiOS interface unit and are slightly warm to the touch.

The sinker seeds were very distressed and I suspect that if I attempted to nick them they would have been destroyed in the process. I don’t expect many of them to germinate. The big question is: are the floaters still viable after the Ortho treatment? I have growing seedlings from this batch of H. moscheutos so I know that some of the seeds were good before the Ortho treatment.

I also stated the forced germination of nine (9) Hibiscus coccineus (White Texas Star) seeds purchased from a very reliable source on eBay. I already have over thirty red and white seedlings from this eBay seed seller and have been pleased with the results. I nicked all nine seeds and put them into hand-hot water and after 12 hours eight (8) of the seeds had sunk. H. moscheutos uses water dispersal and but the H. coccineus I used had already been nicked. I am going to have to see if infected H. moscheutos seeds sink or float without any insecticide treatment. H. moscheutos may have an interesting way of dealing with Althaeus hibisci. Using normal indoor germination techniques I have very limited success with seeds which are not nicked. Hopefully Santa will bring me one of those seedling heating pads soon. Perhaps if I keep germinating seeds in the TV room I will get my wish early!

Speculation:
There is one other possibility which should be considered. Will any Hibiscus seed with a hole in it sink? If this is true then a one day flotation test could be an incredible simple way to separate good and bad seeds. The next batch of seeds which I force germinate with be floated first, then nicked and floated once again to hydrate them. Any seed harboring Althaeus hibisci already has its shell compromised when the larvae entered the seed. I have found lively discussions on the Internet involving sinker vs. floater seed advocates and depending of the species both may be correct. We do have one research paper which states that Hibiscus moscheutos seeds that float are good. Please remember that this is pure speculation on my part right now. Also keep in mind that most of the plants labeled Hibiscus moscheutos are hybrids.

If you have not already done so, read this paper and remember that it only applies to wild Hibiscus moscheutos:

A GENETIC ANALYSIS OF HYDROLOGICALLY DISPERSED SEEDS OF HIBISCUS MOSCHEUTOS (MALVACEAE)
http://www.amjbot.org/cgi/reprint/88/4/588.pdf

Although high seed infestation rate by a bruchid seed beetle, Althaeus hibisci, has been reported in the study area (Kudoh and Whigham, 1998), nonviable seeds rapidly lose their buoyancy (R. Shimamura, Tokyo Metropolitan University, unpublished data).

I have reached out to www.BugGuide.net and offered to send them a batch of my infected Hibiscus seeds, live bugs and all. They have pictures of several suspected Althaeus hibisci sightings but they are not listing them as confirmed identifications at this time. I will even try to collect additional H. moscheutos pods if they are still available with seeds. It is important to the Hibiscus hobbyist’s community that we have verified pictures of this beetle on the Internet. I never want anyone to have to go through this again unawares. We desperately need a treatment protocol to kill Althaeus hibisci in the seeds while not killing the healthy seeds, otherwise anyone in a high risk area should not export Hibiscus seeds in trade. On Bug Guide you can also post eradication techniques or any general information about the bugs on the species page.

I will be running Malathion tests and was wondering if anyone has ideas for concentrations which should be used to soak Hibiscus seeds? I will check the Internet to see if anyone else if bathing seeds in Malathion. After doing some reading there are many safety advantages in using Malathion and I now wish I had tried that first. The dosage regiments on the Spectracide Malathion bottle is not designed for small patches. I took all of the formulations off the Malathion bottle, loaded the data into an Excel spreadsheet, converted the data into Metric and then created formulations for 0.5l (500ml) batches of Malatrhion as that is the size of the spray bottle I have. Concentrated Malathion volumes are given in Drops or Milliliters, which range from 19 drops (0.997ml) to 76 drops (3.907ml) in 500ml of water using Spectracide’s range of recommended published values. I will work with the 19 drops (0.977ml) per 500ml concentration and use a 5 minute immersion of the seeds for starters. My success requirements will be:

1. Safety for the gardner.
2. Kill the Althaeus hibisci.
3. No damage to the viable Hibiscus seeds.

If anyone wants the Malathion Excel spreadsheet send me a DM! I can also convert it to Open Office.

I will continue to update this Hibiscus Forum post:

Mike

I'd had the same problem with my hib seeds (posted a thread about it here w/pictures: http://davesgarden.com/community/forums/t/1039672/). Before I shared/traded any hib seeds, I carefully inspected each one to ensure it didn't have a hole in it before sending them along. Also, I've had mine in the freezer for quite some time now (a month).

Jlj072174,

Yes that is exactly what my seeds with holes look like. The seeds with holes in them are not the problem as the Althaeus hibisci have already emerged. The problem is the seeds without any visible holes. Without controlled studies I am not convinced that freezing will kill the Althaeus hibisci which have not emerged from the Hibiscus seeds. Did you find any research papers on this subject?

Can you provide additional details of the microscope you are using? Those as interesting photographs. If you take the seeds out of the freezer and put them in to a Zip Lock you might be able to get some photographs of Althaeus hibisci if more beetles emerge.

Mike

The microscope is simply a digital one (my daughter's actually) that connects via USB to the computer. You can look at items live, or take pictures of them (which is what I did to get that picture, as my regular camera wouldn't zoom in that far/close.

I didn't find anything else about the insects themselves but I haven't had much time either to look into it. I just threw away the seeds with holes, and froze the rest of mine for a few weeks. I haven't seen any further evidence of the bugs.

On the floaters vs sinkers...I've had floaters germinate so it's not a hard and fast rule, I definitely wouldn't give up on your floaters. And if the Ortho treatment had a negative effect on the seeds, I don't think it would change whether they were going to float or not so I don't think that's going to be how you figure out if the Ortho damaged the seeds or not.

In your experimentation on killing the bugs, I would try another experiment with freezing for a longer period of time. In the three hours that you tried initially, that may not have been enough to kill them but if you leave the seeds in the freezer for longer that may do the trick and would certainly meet your criteria around safety. I would think a week ought to be enough--if that hasn't killed them then longer likely won't either but at least that way you've given the freezer the best shot.

Mike: Wow, that is a lot of great information. You missed your calling. You should have been a plant scientist/ horticulturer.

I live in zone 4. I don't know if weevils are a problem here or not. I know I have never encountered these buggers although I collect plenty of perennial seeds. My Hibiscus bloomed too late to mature the seeds. Hopefully next years.

Here is a thought. If freezing kills these bugs there wouldn't be a problem the following year. Most insects survive below zero temps during the winter to emerge the following spring. Therefore, I doubt freezing the bugged seeds will kill the bugs inside. Brought out into the warmth, they will revive.

On the other hand, is it possible that cooling weather signals to insects to prepare for freezing temperature and do what they need to do to assure their survival. After all, species of birds fly south before winter to survive. Ducks are a good example of that.

When placing bugged seeds in the freezer, there is no safety signal so they can't do anything to prepare for winter. That fact may kill them.

Just a crazy thought to ponder upon.

I had previously commented on the smaller size of wild Hibiscus moscheutos seeds. Attached is a photograph comparing Hibiscus seed sizes of three Hibiscus cultivars, two are species and one is a hybrid. From left to right the seeds in the photograph are the following:

1. Hibiscus moscheutos (Wild seed from New Jersey)
2. Hibiscus x Lord Baltimore
3. Hibiscus coccineus (Red Texas Star)

I tried to select representative seed sizes for all three examples. The picture is actually a family portrait because Lord Baltimore is a hybrid of H. moscheutos, H. coccineus and several other Hibiscus species, some of which are no longer considered species. The plant patent for Lady Baltimore, the pod progeny of Lord Baltimore, provides some documentation for the ancestry of Lord Baltimore and documents the fact that it is “almost” pod sterile with a pollination success rate of 1/250.

http://www.google.com/patents/about?id=KPY8AAAAEBAJ

The hybridization was conducted over a period of years using as seed parent "Lord Baltimore," which first bloomed in 1955. "Lord Baltimore" is itself a near-sterile hybrid, its ancestry including Hibiscus militaris, Hibiscus coccineus, Hibiscus moscheutos, and Hibiscus palustris. Because of the shy seeding habit of "Lord Baltimore" (a flower-to-seedpod ratio of approximately 250 to 1), no attempt was made to keep the crosses exclusive. As far as possible, pollen was manually delivered from selected pink-flowered hibiscus plants; but there was no exclusion of the serendipitous bee. Selections were continuously made from the seedlings so derived.

My single seed pod from Lord Baltimore was the result of manual pollination with it own pollen after many failed attempts. I was incurably lucky to obtain the pod which was not compromised by Althaeus hibisci because it was so late in the season. Using Blomma’s protocol I plan to start artificial germination in a few weeks once I get all my Hibiscus species seeds started.

For seed sizes compare these two calibrated USDA photographs:
Hibiscus moscheutos
http://plants.usda.gov/java/largeImage?imageID=himo_004_ahp.tif
Hibiscus coccineus
http://plants.usda.gov/java/largeImage?imageID=hico2_002_ahp.tif

Almost all hardy Hibiscus cultivates have the seed sizes of H. Coccineus, not H. moscheutos. It would be interesting to do a side by side calibration of the seeds for all North American Hibiscus species.


Mike
p.s. I apologize for the poor quality of my photograph; I am working on a new lens and lighting system for my camera.


This message was edited Nov 21, 2009 10:59 AM

I realized that I could take the two USDA photographs of Hibiscus moscheutos and Hibiscus coccineus seeds and using the calibration bar which appears in both, resize and merge the two images so that the seeds of both species appear to scale relative to each other. I am gratified to note that the size of seeds is consistent with the image I previously posted.

I wonder how many H. moscheutos genes are really in our hardy Hibiscus ornamentals?

Mike

Using the Forum facilities at Bug Guide I was able to establish contact with an entomologist at Minot State University in North Dakota, who was interested in working with my collection of Althaeus hibisci.

Althaeus hibisci Live Specimens Available
http://bugguide.net/node/view/352187

Live specimens of Althaeus hibisci together with the seeds of Hibiscus moscheutos were successfully delivered to the University on Friday November 20, 2009. I am looking forward to photographs and species conformation in about a weeks time. I am becoming increasingly convinced that the relationship between Althaeus hibisci and Hibiscus moscheutos is a symbiosis because Althaeus hibisci may be a pollinator for Hibiscus moscheutos as this paper may suggest.

Visitation of a Specialist Pollen Feeder Althaeus hibisci Olivier (Coleoptera: Bruchidae) to Flowers of Hibiscus moscheutos L. (Malvaceae)
http://www.jstor.org/pss/20063760

Mike

Mike: That is great! You may be correct in that there may be a relationship between Hibiscus and Althaeus hibisci. I would think, though, that if it was to pollinate the bloom, it wouldn't devour the seed later. Nature never build just to tear down.

I received some hardy Hibiscus seeds in trade from a member here on Daves. All were NOID's just named by color. After reading your post above, I checked and found several with holes in them. A magnifying glass revealed that there is nothing in the seed left to produce a seedling. No sense wasting time on them.

Blomma,

If is a very find line between a host/parasite and a symbiotic relationship. The fact that Althaeus hibisci larvae are a Hibiscus moscheutos seed predator doesn’t preclude a symbiosis if Hibiscus moscheutos obtains something is return for the loss of seeds. If Althaeus hibisci is reliable pollinator which transfers pollen between different plants the increase in genetic diversity would be a large advantage to Hibiscus moscheutos. In addition to genetic diversity if Althaeus hibisci increases the production of Hibiscus seeds the increase could offset loss of seeds to the larvae.

We should remember that Hibiscus moscheutos is not defenseless. If the research reports which I have previously referenced are accurate, infected seeds will be drowned by water dispersal. The apparent specificity of Althaeus hibisci to Hibiscus moscheutos suggests a long term relationship.

I am still working with the seeds I treated with Ortho's "Home Defense Max". I have had several surprises but am still working with 37 seeds out of the original 200 I started with on November 14. I should know more in about 3 days and will post my findings then. I have a second batch of Ortho treated seeds which yield a surprise and a larger batch of untreated seeds which are still infected.

Recently, additional Althaeus photographs were posted on Bug Guide, including a picture of a Hibiscus seed with a hole in it and a unspecified member of the Althaeus genus beside it. From the small size of the seed it may well be Hibiscus moscheutos.
http://bugguide.net/node/view/352686

Mike