Final Report for FNC10-843
The small hive beetle was introduced in the US in 1992. It has the ability to destroy and kill a colony of bees. The beetle enters the hive between cracks and crevices as well as the front entrance. The larva does its damage before exiting and pupating into an adult. If we can prevent a suitable soil for pupation, can we eliminate the beetle? The “salt box” method is an integrated pest management approach attacking the small hive beetle. It is chemical free and inexpensive, over the life of the hive. Test results have shown that this method works.
This project dealt primarily with the weakest link of a small hive beetle larvae. How can we keep the larvae from pupating into an adult? The original premise was placing a salty environment beneath the hives that would prevent and kill the larvae before reaching suitable soil. During this testing other methods were reviewed as potential contributors to better control and elimination of the small hive beetle.
The SARE proposal dealt with the weakest link in the small hive beetle lifecycle. Could it be possible to prevent the small hive beetle larvae from developing into adults? The weakest link of the beetle is the need for the small hive beetle larvae to find suitable soil to pupate into an adult small hive beetle. The key objective was to kill the small hive beetle larvae before they were able to pupate into adults using a method called the “salt box.” If we kill all the larvae would there be any adult beetles?
I developed a box that would be placed beneath the hive body boxes of a beehive. The hive would be supported above this box using 4x4 pressure-treated wood cut to 24 inch lengths. It seemed to be the best economical approach to use one 4x4 8 foot length per colony. This box would be filled with pea rock and salt rock on top of a layer of 30 pound roofing paper. (See PIC IMG_0091) My intent was to kill the larvae as they were trying to get down through the rock to favorable soil. This method can be named the “Salt Box.”
During the Salt Box test, I compared other pesticide free methods currently being used to control or kill the small hive beetle. Using the standard banana fermented mixture of bananas, water and sugar as bait, I compared corrugated plastic materials, (see PIC IMG_0322_3) a baited sandwich container trap, (see PIC IMG_0323) existing beetle traps, the external PVC trap developed by the University of Florida Gainesville, (see PIC IMG_0324_3) and screened bottom boards without trays, with trays, and with vegetable oil filled trays.
Setting up 20 test hives, triggered another question, “How can I prove that the Salt Box was actually killing larvae?” To test if this method was working I constructed a test box base identical to the bases used around the beehive. The test box was divided into 10 sections for the purpose of observing the activity of the small hive beetle larvae. (See PIC IMG_0333) Small hive beetles were needed for this test. Three collections of small hive beetle larvae were made after placing pollen patties into two hives providing participants captured for the test.
The test was to determine if any of the larvae would eventually make their way through the pea gravel and rock salt. The test box was placed in front of my house in a shady area. The box had pea gravel and salt rock mixture just like the 20 hive bases.
The first test used 37 larvae, placing them three or four larvae in each section. I sat outside waiting to see if any of the larvae would exit from the bottom of the box; none were observed coming out. During the second test, I had 47 small hive beetles and dispersed them equally within the 10 sections and again no small hive beetle larvae emerged from the bottom of the box. The third test involved 17 larvae placed within the 10 sections. For the third time, no larvae were observed exiting the box. Were the larvae living in the box, or did they die in the box? So I searched the box for the carcasses of the small hive beetle. Then I realized I needed a better testing method. I decided to suspend the box 2 feet above a tin tray that measured 44 inches x 34 inches. This was the end of summer of 2011. (See PIC IMG_0342)
In the summer of 2012, I was able to get back to testing the pea rock and rock salt trap (Salt Box). I already had the base elevated over the tin tray. I first filled the box up with pea rock. (See PIC IMG_0510_1) I had 10 sections again within the box. I captured 74 small hive beetle larvae to be used on my first test. I placed between seven or eight larvae within each section. Shortly after the three minute mark, one of the larvae made it through the pea rock and fell down to the tin tray making a distinct pinging sound. This was slightly discouraging. But it got worse, in the next 18 minutes six more larvae made it through the pea rock making a distinct pinging sound when landing in the tray. All the larvae that made it through the pea rock fell out around the perimeter of the box. All seven of the larvae were placed back into the center of the box after they landed in the tin tray. The rest of the afternoon and into the evening no other larvae made it through the pea rock. My goal is to prevent any of the small hive beetle larvae from making it through.
The next test consisted of covering the pea rock with a layer of rock salt. (See PIC IMG_0515) This test used 82 small hive beetle larvae. Seven or eight small hive beetle larvae were placed in each section. Four of the small hive beetle larvae made it out of the trap. The larvae crawled over the rock salt up the side of the wood falling down onto the tin tray making the very distinct pinging sound. The larvae were recaptured and placed in the center of the test box. This all happened within the first three minutes of the test. No other larvae made it over the side or down between the pea rock. As I was sitting there watching this test I had a bag of topsoil and a bag of sand sitting in my garden. This made me think to set up smaller testing samples using plastic containers.
The first plastic container contained only sand, the second container contained only topsoil, the third container contained pea rock covered with rock salt, and the fourth container was layered with topsoil over the rock salt/pea rock combination.
Five larvae were placed in the container of sand. The larvae were forced to the edge of the plastic container being unable to burrow through the sand. The five larvae continued to walk around the edge of the plastic container and eventually died within 14 days.
Five larvae were placed in the middle of the topsoil container. Within seconds the larvae burrowed down into the dirt. It was so fast I was not even able to get my camera ready to take a picture of the event. (See PIC IMG_0512)
Five larvae were placed in the container of mixed pea rock and rock salt. Some of the larvae proceeded down between the rock salt. Two of them walked to the edge of the plastic container. These two small hive beetle larvae walked around the edge until they were able to find an opening downward. It was possible to watch one of the larvae travel along the edge of the plastic until it finally got stuck and couldn't back up and died.
Into the fourth container that was layered with topsoil, rock salt, and pea gravel, five larvae were placed in the middle of this container. Again within seconds the larvae went through the dirt into the rock salt, pea rock. None of the larvae made contact with the plastic container.
After performing these four sample tests, I decided to add topsoil to my Salt Box. (See PIC IMG_0524) Observing that small hive beetles instinctively proceed downward as soon as they find a favorable location, and that small high beetle larvae have no instinct for going back up, I was anxious to try a new test. I tested with 88 small hive beetle larvae. Placing between eight and nine in each section, by the time I placed the last group in the last section most of the previous larvae were already burrowed through the topsoil. I sat outside next to my test for five hours. I now know why professors have grad students. Zero larvae made it through the topsoil, rock salt, pea gravel combination. I continued to observe the test, listening for that distinct pinging sound and looked for larvae in the tin tray. The following day it rained about a quarter of an inch filling the tin tray with water. No larvae were observed.
Impact of Results/Outcomes
The salt box method does work providing an integrated pest management approach to kill and potentially eliminate the small hive beetle. Testing different soils and visually watching the beetles try to find suitable pupating areas, I can conclusively say with a guarantee that the salt box method works. I am in the process of developing a product that can help control small hive beetles.
Educational & Outreach Activities
Currently I am attempting to publish an article about these trials in magazines. I have given presentations to local bee keepers about this method. I was a participant in the Heartland Apiary Society conference that was held in St. Louis, MO in 2012. I presented my project at 3 seminars. My goal is to give this presentation to more bee clubs and pursue a location where I can conduct a larger test.
A video presentation from the 2012 NCR-SARE Farmers Forum at the National Small Farm Trade Show & Conference can be viewed online through NCR-SARE's YouTube channel. Please use the following link to view it: https://youtu.be/uJLwxe0hOa0
The plan for 2013 is to build a larger salt box. I am presently involved with one beekeeper with a heavy infestation of small hive beetles. I will be creating a 4 x 8 salt box for him to place his hives in the middle of this box. The objective is to see if the small hive beetle population starts to decrease. The box will be constructed using a piece of 4 x 8 pressure-treated plywood attached with 2 x 6 pressure-treated boards screwed around the perimeter. The box is lined with 15 pound roofing paper. The beehives will be placed in the center supported by the 4 x 4 columns coated with Tanglefoot. The box will have a layer of pea gravel with rock salt topped with less than an inch of topsoil. Any method similar to this should work providing that the rock salt environment is present beneath the hive.
The small hive beetle genetically developed to live inside the honey bee colonies eco-system. Small hive beetles are living in this universe of food sources and shelter so why would they be attracted to a trap inside the beehive. To control a small hive beetle population you have to keep them from entering the hive. The larvae of the small hive beetle would have to be killed before they become adult beetles. One of the things we should do first is make our colonies harder for the beetle to enter. Second is use the Salt Box method with stationary hives and develop a honey bee through selective breeding that is aggressive to the point of killing the small hive beetles and its larvae. I am currently developing and working on solutions in these areas.
If the small hive beetle larvae are kept from developing into an adult beetle, can we eliminate the small hive beetle from North America? If you keep offspring from developing into reproductive adults eventually that species will become extinct. But does this answer the question? There will always be a presence of small hive beetles in North America. Beekeepers who have stationary beehives can build a salt box base around their beehive to kill the larvae. I will say that this method is guaranteed to kill the small hive beetle larvae.
An external pheromone trap that attracts the female small hive beetle would be beneficial. I am currently testing a dry pollen feeder. This should eliminate one of the main attractors to the small hive beetle: pollen patties. The dry pollen feeder will also be tested as an external trap using the pollen patty and number 8 wire mesh. The pollen patty would be chemically treated to kill the beetle but will prevent bees from entering the trap. I have currently received training in artificial insemination hoping to develop a bee that shows aggressiveness towards small hive beetles.