A Push-pull Protocol to Reduce Colonization of Bird Nest Boxes by Honey Bees

Summary

Preventing colonization of bird nest boxes by invasive Africanized honey bees is important for conservation efforts of nest-site limited birds. We provide an integrated pest management approach to "push" bees away from nest boxes with a repellant insecticide, permethrin, and "pull" them toward pheromone baited swarm traps.

Abstract

Introduction of the invasive Africanized honey bee (AHB) into the Neotropics is a serious problem for many cavity nesting birds, specifically parrots. These bees select cavities that are suitable nest sites for birds, resulting in competition. The difficulty of removing bees and their defensive behavior makes a prevention protocol necessary. Here, we describe a push-pull integrated pest management protocol to deter bees from inhabiting bird boxes by applying a bird safe insecticide, permethrin, to repel bees from nest boxes, while simultaneously attracting them to pheromone-baited swarm traps. Shown here is an example experiment using Barn Owl nest boxes. This protocol successfully reduced colonization of Barn Owl nest boxes by Africanized honey bees. This protocol is flexible, allowing adjustments to accommodate a wide range of bird species and habitats. This protocol could benefit conservation efforts where AHB are located.

Introduction

Since the accidental introduction of more than two dozen African honey bee queens into Sao Paulo, Brazil in 1957¹, these insects have spread throughout South and Central America and up into the southern United States, usurping and replacing the less well adapted European honey bees (EHB) in the feral population. These hybrid Africanized honey bees (AHB) have traits that put them in conflict with both humans and wildlife. They exhibit highly defensive behavior, reproduce very fast, and are less selective about where they make a home^1,2.

Although nest boxes have long been used by ornithologists to enhance breeding by cavity-nesting birds^3,4, their use has been shown to be especially effective for enhancing the breeding of threatened and endangered parrots in the tropics^5,6. Unfortunately, Africanized honey bees often choose these same nest boxes – sometimes even killing the occupants. Additionally, these AHB pose a significant threat to biologists when they are conducting nest studies. In areas of South America where AHB have been established, several parrot conservation projects have seen their artificial nest boxes occupied by AHB^7-10. Competition for nest boxes with honey bees is widespread and is not confined to parrots. Many other bird species both in the New and Old World are affected^11-15. Without efforts to mitigate the threat of these invasive AHB, recent successes in parrot conservation could be lost.

Current practices for managing competition from bees includes the use of repeated, high doses of permethrin⁷, manually removing swarms, closing nest entrances immediately after breeding season⁸, or the application of chemicals to the outsides of nest boxes¹⁵. The labor involved and the danger to biologists render these strategies less than optimal. Development of a prevention protocol is warranted.

Honey bee colonies multiply via a process known as swarming, when the old queen leaves the colony with up to three fourths of the worker bees¹⁶. Africanized honey bees' high reproductive rate allows them to swarm more frequently (four to eight times per year) than EHB (who swarm once or twice per year)¹⁷. Moreover, AHB may swarm throughout the year rather than during a particular season like EHB. Consequently, AHB can quickly occupy most of the suitable nesting sites in a given area.

Honey bee house hunting behavior can be utilized to influence their choice of nest site. A small fraction of bees in a swarm fly off to locate and inspect new potential nest sites. Several potential nest sites are scouted for simultaneously. These scout bees return to the swarm and perform dances to indicate the location of the site. The stronger the dancing is for a site, the faster the number of scout bees builds up at that site¹⁸. Therefore, bees dance stronger for better quality sites, compared to sites that are mediocre or poor. Once a quorum threshold is reached, the swarm takes off and flies to the new chosen home site¹⁸.

Sub-lethal contact doses of the insecticide permethrin hamper a scout bee's ability to orient and reduce its activity level^19,20. An application of permethrin inside nest boxes at first should be repellant to scout bees²¹, and overtime as the chemical degrades, scout bees exposed to permethrin during their assessment of the box, should be rendered less able to perform strong recruitment dances, decreasing the amount of scout bees recruited to the site. A more suitable (ideal cavity volume, small entrance hole located at the bottom, and a pheromone attractant) alternate nest site is provided in the form of a trap box for the bees. This excellent trap site should reach a quorum faster than the insecticide treated bird box leading the swarm to choose the trap box over the bird box.

As an example, we describe an experiment to reduce colonization of Barn Owl artificial nest boxes by AHB in South Florida sugarcane fields. Our objective was to test the effectiveness of using a push-pull method that will "push" bees away from owl nest boxes treated with an insecticide and "pull" them toward pheromone baited swarm traps.

Protocol

1. Construction of Swarm Trap Boxes

NOTE: There are two alternate protocols for swarm trap construction included as steps 1.1 and 1.2. There are several additional ways trap boxes could be constructed. The following two methods are presented here because we have tested them in experiments and they have been successful. For either protocol, use 1.3 cm to 2 cm thick non-pressure treated plywood.

1. Construction of Swarm Trap Protocol Option 1: Building a Trap Box
   1. Cut six pieces of plywood 30 cm x 30 cm.
   2. Attach the four sides of the box together with nails or screws.
   3. Attach the bottom piece by nails or screws.
   4. Attach the top piece with screws or staples.
      1. Do not use nails to secure the top. The top must be removable to get bees out and clean the box.
   5. Drill a 2.5 cm hole in the middle of one face of the trap box 2.5 cm from the bottom edge.
   6. Apply primer, sealant, or paint to the outside of the trap box to protect wood from weather.
      1. Do not apply any paint or sealant to the inside of the trap box. This could be repellant or toxic to the bees.
2. Construction of Swarm Trap Box Protocol Option 2: Use of a Standard Deep Hive Body
   1. Obtain a standard 10 frame deep hive body from a local bee supply store.
   2. Cut a top and bottom from plywood each measuring 50.8 cm long by 41.3 cm wide.
   3. Attach the bottom piece by nails or screws.
   4. Attach the top piece with screws or staples.
      1. Do not use nails to secure the top. The top must be removable to get bees out and clean the box.
   5. Drill a 2.5 cm hole in the middle on one side of the trap box 2.5 cm from the bottom edge.
   6. Apply primer, sealant, or paint to the outside of the trap box to protect wood from weather.
      1. Do not apply any paint or sealant to the inside of the trap box. This could be repellant or toxic to the bees.

2. Preparation of the Pheromone Lure

1. Prepare a mixture of citral and geraniol at a 2:1 ratio.
2. Place 1 ml of this mixture into a snap-top 1.5 ml polypropylene microcentrifugation tube.
3. Wrap lures in aluminum foil to protect them from light.
   Note: The cap of the centrifugation tube is punctured with a push pin when it is placed in the mounted swarm trap.
   Note: Lures can be stored in a dark place at RT or for longer storage in a -10 °C freezer.

3. Installation of Swarm Trap Boxes

NOTE: There are two alternate protocols for the installation of swarm trap boxes presented in steps 3.1 and 3.2.

1. Installation of Swarm Trap Box Protocol Option 1: Installation on a Post
   1. Place a 10 cm by 10 cm pressure treated wood fence post into the ground 10 m to 15 m from where the bird nest box is located.
   2. Construct a hanging board of 1.3 cm thick pressure treated wood measuring 20 cm by 20 cm.
   3. Align the hanging board in the middle of one side of the trap box, with 10 cm above the top of the box. Secure the board to the box with at least two nails or screws on either side of the board.
   4. Place the trap box on the post at a height (1.5 m to 3 m) that is safe and easy for removal when the trap box is colonized by bees. Screw the box to the post by attaching the hanging board. Place a screw approximately 5 cm below the top of the hanging board and screw in place.
      1. Do not use nails because they are difficult to remove.
2. Installation of Swarm Trap Box Protocol Option 2: Installation on a Tree
   1. Drill a 5 mm hole in the upper back corner of each side of the box.
   2. Thread a wire through the holes.
      Note: If using this protocol it will be easier to put the wire through the holes prior to securing the top of the box.
   3. Select a tree approximately 10 m to 15 m away from where the bird nest box is located.
      1. Do not place trap boxes in the same trees as bird boxes because when someone checks on the status of the bird box, trap boxes colonized by bees may be disturbed causing bees to become defensive.
   4. Secure the wire around the tree 1.5 m to 3 m off the ground.
      Note: To protect the tree, a cambium saver can be used around the wire.
      1. Make sure the box is level and secure so that it does not tip over. The box can be rested on a tree branch for added stability if available.

4. Addition of the Pheromone Lure

1. Take a previously prepared lure from section 2 and puncture the top of the tube with a push pin.
2. Place the lure inside the trap box on the bottom near the entrance after installation to ensure it does not fall out while installing the box.

5. Treatment of Bird Nest Box with Permethrin

1. Select a permethrin product that is labeled for use in poultry or caged birds only.
2. Follow label instructions for mixing and application
   CAUTION: follow any personal protection guidelines on label recommendations.
3. Spray the inside of the nest box entirely, until the point that the liquid runs off the sides of the box using a 3.7 L hand pump sprayer.
   Note: Nest boxes can be treated prior to or after installation.

6. Removal of a Trap Box Occupied by Honey Bees

1. Plug the entrance hole with a small towel.
   CAUTION: wear proper protective garments to prevent stings from honey bees.
   1. If swarm is to be killed, do so as soon as discovered. If swarm is to be utilized, allow bees to fully colonize trap boxes before attempting to remove them (usually about 2 weeks). If possible, remove occupied trap boxes at night (when all the bees are inside). The trap entrance can be plugged at night and then the box removed the following morning in daylight.
      Note: Use a red filtered light when working around bees at night.
2. Unscrew the box from the post or cut the wire holding the box to the tree.
3. Move the box to its new location (at least 4 km away) and pull the towel out from the entrance hole.

7. Destruction of Bee Colony in Trap Box

Note: In areas where it is illegal to keep Africanized honey bees, destruction of the colony may be warranted. If so, two protocols are presented here.

1. Solarizing the Colony
   1. Plug the entrance hole with a small towel.
      CAUTION: wear proper protective garments to prevent stings from honey bees.
   2. Unscrew the box from the post or cut the wire holding the box to the tree.
   3. Enclose and seal the trap box completely in a plastic bag and leave in full sun for several days
      CAUTION: wear proper protective garments to prevent stings from honey bees.
   4. Clean out the box by removing dead bees and comb.
2. Use of an Insecticide Spray
   1. Use an insecticide spray labeled for use to kill bees to spray inside the trap box.
      CAUTION: follow label instructions on insecticide and use appropriate personal protection equipment to prevent stings from honey bees.
   2. Plug the entrance and leave the box for 24 hr.
   3. Clean out the box by removing dead bees and comb.
      Note: To reuse the trap box clean the inside with a soapy water solution to remove residual insecticide. Rinse well and allow to dry completely before reinstalling.
3. Use of an insecticide foam
   1. Fill the entire cavity of the occupied trap with a detergent-based foam. (CAUTION: follow label instructions on insecticide and use appropriate personal protection equipment and wear proper protective garments to prevent stings from honey bees).
      Note: The foam can be applied with a commercial pest control foam generator or a compressed air fire extinguisher.  
      Note: For using a fire extinguisher: Place 3.8 L of water into a 9.5 L fire extinguisher, add  190 ml of foaming agent (or dish washing detergent), seal the extinguisher, and pressurize it to 100-125  pounds/sq. inch (psi).  Just prior to use, agitate vigorously, and then apply the foam until the trap is overflowing.  
      Note: Foam kills the bees within 60 sec by entering the spiracles and blocking the trachea.
   2. Plug the entrance and leave the box for 24 hr.
   3. Clean out the box by removing dead bees and comb.
      Note: To reuse the trap box clean the inside with a soapy water solution to remove residual insecticide. Rinse well and allow to dry completely before reinstalling.

Results

A previous small pilot push-pull study conducted in Brazil showed swarm traps were effective and reduced bee occupation of parrot nest boxes²². To determine if the push-pull method can be effective at a larger scale to reduce colonization of bird nest boxes by AHB, we conducted a field study in sugarcane fields in southern Florida, USA. Sixty Barn Owl nest boxes were installed and each was paired with a swarm trap located 15 m away. Every swarm trap received a pheromone lure. O...

Discussion

As a highly successful invasive insect¹⁷, AHB constitute a major competitor for cavity-nesting birds throughout their range. The protocol presented here is designed to reduce the colonization rates of bird nest boxes by AHB. The main components of this design include 1) the use of a repellant and bird-safe insecticide, permethrin; 2) The provision of an alternate nesting site for bees; and 3) the use of an attractant pheromone inside trap boxes. Bees usually make the "right" decision when choosing a ne...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Citral (ACROS Organics)	Fisher Scientific	AC11044-1000
Geraniol (ACROS Organics)	Fisher Scientific	AC41090-1000
PermaCap CS	BASF		controlled release permethrin