The European Hornet dilemma
Working Draft 1
The Benefits of this non native species of Hornet in the US are outweighed by the actual damages caused by its very well established feeding habits.
1. Known Effect Girdling. Girdling occurs when an insect removes the bark in a section of a tree or limb spanning the circumference of the trunk or limb. This in effect causes the injury to leak sap. This sap is collected for food for larvae and the nest. The damage to the trees is permanent
2. Honey Bee decimation. The European hornet will attack native and domesticated hives for the honey and pupae. This in turn removes from the Eco-system the single most contributing factor for pollination of agricultural commodities and fruits.
When seen from a single nest perspective this seems manageable. But when seen from a larger but comprehensible perspective the effects of this species is shocking.
Nest sizes Can range from as few as 300 to as many as 1000 hornets. The social structure being similar to the bald face hornet or yellow jacket social models.
Queen- Lays the eggs
Non Fertile Females- tend to the queen and the eggs- pupae-larvae
Workers- bring food to the nest. Expand then nest- Maintain the nest
Scouts- Search for food
Later stage of Nest
Queen produces fertile females and fertile males. Food requirement goes up for the nest and aggressive behavior starts to increase
In Culpeper County my 2000 survey indicated 100 nests present within a 15 mile radius of the Town of Culpeper proper. That is 30,000 to 100,000 hornets.
If only 10 percent of the nest girdled one limb per summer that is 3,000-10,000 limbs destroyed.
If 10 native or domestic honey bee hives are destroyed that is an untold amount of crop loss as well as vital Eco-system pollination that cannot occur.
The impact upon the European Hornet by birds and other insect feeders is minimal and the nesting habits make it difficult to locate and reduce their numbers to a manageable level.
European Hornets prefer hollow standing trees. With a cavity close to the size of a football. Over the course of a season they will have enlarged the cavity to the size of a basket ball or more.
Naturally the bigger the cavity the larger the Nest.
They DO reuse the tree. It may not be the Over Winter Queen but A queen will find the old nest and reuse the cavity. I have Two study trees; one at 810 Fairfax street and one at 24807 Revercomb that have seen continuous use since the late 1990s.Similar reports have been submitted from across the state verifying this occurrence.
Walls and Standing structures. Any Structures that meet the same physical characteristics of a tree cavity will be used by the hornets as such. For residential areas this can be a problem for the residents. For allergic children this can be deadly.
Controlling and Management:
For Standing structure it is best to Screen and seal any open cavity’s in walls , fascia boards, soffets and vents.
For trees in the winter on can seal the cavity’s closed after a treatment of Drione or Demise (ACTIVE INGREDIENTS:
Pyrethrins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.00%
* Piperonyl butoxide, Technical . . . . . . . . . . . . . . . .10.00%
Silicon Dioxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60.00%
INERT INGREDIENTS: . . . . . . . . . . . . . . . . . . . . . . . . . . 29.00%
TOTAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100.00%
* Equivalent to 8.00% (butylcarbityl)(6-propylpiperonyl) ether and 2.00% related compounds is applied. Chemical treatment should be done by a certified professional.
Early Spring. Before first bloom it is advised to pretreat flowering trees with timed release vectoring chemicals (TRVC) such as Optigard (Thiamethoxam ). These chemicals attach to the hornets upon contact as they seek to girdle the tree. Once carried to the nest the chemical is transferred to the nest and to other hornets who come into contact with the host. 4-7 days later the chemical activates and the nest begins to die. 14 days later the nest has been eradicated.
The European hornet prefers to hunt at night. They are attracted to light the same as their prey Moths and large beetles. By using the same TRVC Around the light on outdoor ceilings and high on walls and door jambs you will contaminate the scout and workers who come seeking food.
This method is preferred as it targets only the European hornet and does not expose the residents or workers to the inherent risks of nest location.
Standing tree Cavity Winter Core Temperatures Pre-nest and Post nest.
Hypothesis: Nest waste and bio mass breakdown of the tree core keep the temperatures up to a pre hibernation level. In effect keeping the hornets alive longer or putting more than just one queen in an over winter state.
Test subjects 810 and 24807
Methods of measurement
Electrical outdoor thermometers with coupled sensors.
Over winter Thermal Specs for European Hornets.
The aggressive nature of the hornet appears to be chained to the temperature. With colder climes the Hornet is passive. As the temperature climbs the Aggressiveness of the Hornets increase to the point of outright hostility to any carbon dioxide emitting entities or devices.
The European hornet has an airspeed of 25 miles per hour and can travel 60 miles in a day. With optimum weather it will never travel more than a mile from its nest. As conditions worsen it begins to venture further out.
I have seen this Hornet co exist with wasps and yellow jackets and not exhibiting the eradication behavior that it has with honey bees. It may during times of drought that they attack these wasp and yellow jacket nests but to date in 25 years of observation I have not seen them target those two species for eradication. As this is not a predictable characteristic I find the Potential of this activity as not being a viable reason to sustain over the damage they reliably cause.
The potentiality to be beneficial is just that potential. The actuality is that they cause damage to the nesting tree and Host/feeder trees, they reduce pollination of Crops and Natural resources.
Host trees . Trees that have been hollowed out by carpenter ants are the preferred target for the European hornet. First it has a readily available food supply and second the extent of the cavity is large enough to ensure a successful hornet population. The damage to the host is irreversible and the tree if in a residential area must be removed to prevent loss of life or property.
Maple, Dogwood, Laurel including mountain laurel, fruit trees, rose bushes, persimmon, cherry .
Vines including wild grape and domesticated. Any flower bearing ornamental tree is also a food supply for the European hornet.
Trees I have noticed a preference for are Gum Oaks. Trees they avoid are cedars.