The Return of the Yellowjackets

Mid Summer, and the yellowjackets are back. The first indication: one or two, madly dashing about an outdoor table loaded with food and drink.  

Paper Wasp

And that's the big difference between a yellowjacket and a paper wasp: yellowjackets resemble highly caffeinated bees, who can't seem to sit still for very long, searching for protein and sweets. Paper wasps tend to fly a bit more lazily, in a straight line, with their rear legs hanging down. They are more interested in their nest building than they are in your food.

Yellow Jacket

Of the two, yellowjackets are more aggressive. Paper wasps will only attack you if you mess with their nests, which tend to hang beneath the eaves of the roof line or tucked away inside pipes or wood piles.

paper wasps like nesting in satellite dish pipes!

Since yellowjackets are more of a threat to your backyard picnic plans, here are some fun facts:

• The Western Yellowjacket (Vespula pensylvanica, sometimes called the "meat bee,") is a major pest in California because it can develop large colonies, up to 5000 workers.

• Yellowjacket workers have been known to forage up to 1800 feet from the nest, but the normal foraging range is about 1100 feet. 

• Most yellowjacket species are beneficial to man because they feed on live insects (including webworms, crane flies, flies and caterpillars), animal carcasses, and food in garbage cans and picnic sites.

 
• It is a ground nester, usually in abandoned rodent burrows. But other protected cavities, like voids in walls and ceilings of houses, sometimes are selected as nesting sites.

• Never crush a yellowjacket. A dying yellowjacket worker releases an alarm pheromone that alerts its nest mates. In just a few seconds, you could find yourself surrounded by angry wasps.

• You can lessen your attractiveness to yellowjackets if you forego the use of hairspray, perfume, or aftershave and don’t wear bright-colored clothing, especially bright yellow, light blue, red, or orange. Good choices are white or light tan fabrics which are unattractive to them.

• Yellowjacket nests in East Texas have been unearthed that were over 6 feet across and contained over 1 million cells.

• The number of workers in the nest will reach its highest population level in late summer, then the numbers begin to gradually decline until the onset of significant rainfall.

• Once food is discovered by wasps, they will continue to hunt around that location long after the source has been removed.
 
• When a yellowjacket nest is disturbed, defending workers may attack in numbers and inflict enough stings to create a life threatening situation for individuals hypersensitive to the venom.
 
• If disturbed, yellowjackets can inflict multiple stings and will chase the source of the disturbance as far as 200 to 300 yards from the nest.

• Yellowjackets do not usually sting when away from the nest. Unlike honey bees, these insects have a smooth stinger and can sting repeatedly. 

• If you are stung, cooling the area with ice may be soothing.

• If chased by these angry insects, run away in a zig-zag pattern, and seek shelter in a building or automobile. Do not jump in water...they WILL wait for you to surface.
 
• If you do end up in an area where yellowjackets are present, don't swat them. This will only increase your chances of being stung.

• Try to remain calm and walk away.

CONTROL TECHNIQUES

• Reduce available water for nest building and drinking, by repairing defective spigots and promote drainage in areas where water can accumulate.

• When nuisance wasps are present in the outdoor environment, keep foods (including pet food) and drinks covered or inside the house and keep garbage in tightly sealed garbage cans. 

• Use a red light to locate the nest opening because yellowjackets cannot see red light. 
 
• If wasp nests must be eliminated, it is easiest and safest to call for professional help. In some areas of California, personnel from a local Mosquito and Vector Control District may be available to remove nests. To determine if this service is available in your area, call the California Mosquito and Vector Control Association at (916) 440-0826.

LURE TRAPS
 

• Yellowjacket lure traps work best as queen traps in late winter and spring. In summer and fall they may assist in reducing localized foraging workers, but they do not eliminate large populations.

• Lure traps contain a chemical that attracts yellowjackets into the traps, but common lures such as heptyl butyrate are not equally attractive to all species. 

• Proteins such as lunchmeat can be added as an attractant and are believed to improve catches.

• During spring, baited lure traps should have the chemical bait changed every 6 to 8 weeks.

• In summer, change the bait every 2 to 4 weeks; change bait more frequently when temperatures are high. Meats must be replaced more frequently because yellowjackets are not attracted to rotting meat.

• If commercial lure traps contain live yellowjackets, freeze it for two or three hours before disposing of them. Then, clean the trap and rebait it.

WATER TRAPS

• Water traps are generally homemade and consist of a 5-gallon bucket, string, and protein bait (turkey ham, fish, or liver works well; do not use cat food because it may repel the yellowjackets after a few days). 

• The bucket is filled with soapy water and the protein bait is suspended 1 to 2 inches above the water. (The use of a wide mesh screen over the bucket will help prevent other animals from reaching and consuming the bait.) 

• After the yellowjacket removes the protein, it flies down and becomes trapped in the water and drowns.

• Like the lure trap, water traps also work best as queen traps in late winter to early spring. In summer and fall they may assist in reducing localized foraging workers but usually not to acceptable levels.

• Another home made yellowjacket trap that some report success with: a one or two liter soda bottle. The internet is full of these (unverified) techniques.

• Place any yellowjacket traps at the perimeter of your recreation area, preferably 30 feet.

• Keep screen doors and windows in good repair.

• Gather up ripe or rotting fruit that has dropped from fruit trees.

• Try to observe what food the yellowjackets are after and make it less available to them.

• Use garbage cans with tight-fitting lids and keep them closed.

• Wear shoes when walking through lawns.

• Keep car windows closed whenever possible.

• Be cautious when working in the garden or trimming hedges.

• Be careful when drinking from a can or bottle, as you may swallow a yellowjacket and receive a sting in the throat.

 Sources include:

University of California IPM Project 

Tomatoes Love Basil...Or Do They? Ask the Snarky Farmer!

 It smells like Friday.  Time to...Ask the Snarky Farmer!

Paul in Sacramento writes: 

"I have a conjecture that I need to have validated, or otherwise. Could it be that the proximity of my basil plants to the tomato plants has anything to do with the lack of tomato hornworms? The vapors from the basil are wonderfully aromatic. Have I, in any way, gotten something right without even trying?"

 

Paul:
Here is a link to a rather lengthy, scholarly paper from West Virginia University on the subject of companion planting, including the relationship of tomatoes and basil.

To sum up the research briefly: No, Paul, you haven't, at least not in the way you intended. But you may have encouraged the tomato plants to grow stronger.


The longer answer,  from that PhD dissertation:   
"The earlier data showed that there is no scientific evidence that the odors from highly aromatic plants can actually deter pest insects. This, therefore, brings into question how these aromatic plants produce their effects. The studies reported here showed the relationship of tomato to basil to be one of domination, with a net benefit accruing to the gardener from basil’s ability to survive and produce some yield without compromising tomato yield. Although companion planting has significant effects on some insect pests at the garden scale, these effects are not simply due to the combination of certain companion species. High density plantings can optimize land use efficiency and diculture advantages, but may lead to reductions in crop quality, or management difficulties. The combination of a dominant and subordinate crop results in larger dominant plants and smaller subordinate plants than in equivalent monocultures grown at the same density. Such combinations offer yield advantages when the increase in dominant plant weights exceeds the reduction in subordinate plant weights, suggesting that the two crops draw on slightly different resource sets. Combinations with high subordinate crop proportions may offer the greatest yield advantages."

Another interesting facet of that study asks the question that many gardeners assume as gospel: 
Do tomatoes, when planted with basil, taste better?

If you are squinting to try to figure out that chart, allow me to interpret the results of that test: there is little, if any taste difference. 


But Paul, you still are asking a good question. Where did the tomato hornworms go? I have heard from many gardeners that hornworms just aren't the problem they used to be. Again, that study hints at a possible reason:

"Ground beetles and harvest spiders prey on caterpillars at a higher rate in polycultures" (Dempster and Coaker 1974).

 Because of shrinking yard size and the influence of such books as Mel Bartholomew's "Square Foot Gardening", more and more backyard gardeners are cramming lots of different vegetables together in a planting bed: a polyculture.


And yet another "garden good guy" (although many think ill of this creature), the European paper wasp, is at work on hornworms, according to Dr. Whitney Crenshaw of Colorado State University:

"The European paper wasp has been huge out here in recent years. It took over in a phenomenally short period of time. In addition to the stinging/nuisance issues (complicated by its very close superficial similarity to the western yellowjacket), the insect has decimated backyard Lepidoptera. It has had such an impact that I no longer discuss cabbageworms or hornworms in Master Gardener programs – they are too rare. Also, I usually drop butterfly gardening as a topic, as they eat the butterfly larvae."


And don't forget the help tomato growers get from the ubiquitous (and hungry) backyard birds. Build it (a bird-friendly garden), and they will come. So what if you lose a few tomatoes along with the worms?