Utah Pests News Fall 2011

Utah Pests News 

click here for pdf version



Beneficial True Bugs:
Damsel Bugs

The Economic Injury Level

European Earwig

General Concepts of
Biological Control

The Integrated Pest
Management Concept

Successful Pest Management

Peach Leaf Curl

Pear Sawfly

Walnut Thousand Cankers


Diane Alston 

Ryan Davis
Arthropod Diagnostician 

Marion Murray
IPM Project Leader
Editor, Utah Pests News

Claudia Nischwitz
Extension Plant Pathologist

Ricardo Ramirez
Extension Entomologist

Cory Vorel
USU CAPS Coordinator

Utah Plant Pest Diagnostic Lab
BNR Room 203
Utah State University
5305 Old Main Hill
Logan, UT 84322

Utah Pests News is published quarterly.

To subscribe, click here.

All images © UTAH PESTS and USU Extension unless otherwise credited



Additional articles in this issue:

Organizing a Grasshopper Control Program

Active Beetles in Turfgrass

CAPS Update: Japanese Beetle

Honey Bees as Structural Pests

Biopesticides are the Next Generation of Pest Control Products

Raspberry Cane Damage Abundant in 2011

Fungicide Resistance in Home Garden

News, Publications, and Websites

Trick, or Treat?
Spooky Fall Spider Activity

Adult female hobo spiders are now laying white egg sacs, and they will hatch next spring from mid-May to mid-June. 

Fall is the season for spider encounters in Utah. Many spiders are nearing the end of their life, searching for mates and laying eggs, habits which usually increase the chance of human-spider interactions. Below is a description of the spiders commonly encountered in Utah during the fall months.


By far, the spider most commonly seen in fall is the hobo. Populations are large in northern Utah, and when male spiders leave their webs in search of mates they often find their way indoors. Much has been written on the subject of hobo spiders, and the UPPDL recently created a comprehensive website that addresses most hobo questions.

  Adult female wolf spiders carry spiderlings on their backs.


Wolf spiders are ground hunting spiders, pursuing prey in lawns and gardens. They do not spend much time in webs. This time of year females can be seen with their egg sacs attached to the rear of their body (spinnerets). When the eggs hatch, the small piderlings climb up on the mother’s abdomen and stay there for about a week before dispersing. Large spiders in the genus Hogna cause particular concern this time of year, but like all wolf spiders, they are not poisonous to humans.


The two most marvelous spiders Utahns might encounter are the banded orb-weaver and the cat-face spider (shown below). The adult female banded orb-weaver has a large, oval-shaped abdomen adorned with black, yellow, and white stripes, and black bands on the legs. The cat-face female has a large, oddly shaped abdomen that resembles the face of a cat when viewed from the proper angle.

Cat-face spiders are attracted to porch lights where their perfectly shaped orb webs pluck flying insects from the air. This time of year the females can sometimes wander inside homes or other enclosures in search of an egg laying site. After the eggs are laid, females will likely die. The eggs will hatch next spring, and spiderlings will climb up structures and plants, release long strands of silk and “balloon” away in the wind to new sites.

  Adult female banded orb-weaving spider (top left), adult female cat-face spider (top right), golden huntsman spider (bottom left), and tarantula (bottom right).


Golden huntsman is the most common huntsman spider identified by the UPPDL. These large spiders are a beautiful gold color with black mouthparts and dense black hairs on the end of their legs, giving the appearance of dark socks. These “socks” allow this spider to climb up almost any surface. They are commonly found under the bark of trees or in narrow, secluded places.


Utah is on the northern border of the tarantula’s native range, but at times, these spiders can be found as far north as Cache County. In the fall, male tarantulas leave their underground burrows and migrate in search of female mates, sometimes into home landscapes. The genus of tarantula found in Utah (Aphonopelma) is not harmful to humans.


None of the above spiders should be feared. The influx of spiders usually ends in late October, and tolerance of these beneficial creatures is the ideal strategy. However, if one of the above spiders enters a home, put an open container on top of the spider and slide a piece of paper under the opening. Then, flip the container and paper together, trapping the spider inside. The spider can then be safely released outdoors. If additional control measures are desired, one or a combination of the techniques that follow are recommended.


  • Seal all cracks and crevices (foundation, etc.) leading into the home with silicon caulk.
  • Install weather stripping around doors and windows, especially all doors leading to the outside, including the garage door.

Cleaning and Habitat Modification

  • Vacuum regularly. Spiders, webs, and egg sacs can be vacuumed up, directly eliminating spiders (except hobo egg sacs, which are found outdoors).
  • Minimize clutter. Spiders love secluded places to hide and lay egg sacs. Simplify the environment inside by cleaning regularly and storing clutter in sealable storage bins. Outside, move rock and wood piles or anything that creates spider habitat away from the home.
  • Change exterior lighting. Insects are attracted to exterior lights at night, which in turn will attract spiders looking for food. Replace regular light bulbs with sodium vapor lights which are less attractive to insects.


  • Sticky traps. Standard sticky traps, which are available at garden centers, can be placed around baseboards to help determine which type of ground dwelling spiders are present and where they are coming from. They can also provide some level of control. For hobos, pheromone traps are more effective, but they may attract more spiders to the area, including from outdoors. Avoid using hobo pheromone-baited traps from August to October in Utah.


If an infestation of spiders is present, use the following techniques.

  • In secluded areas (crawl spaces, cracks and crevices, or any area where people won’t come in contact with chemicals), use a dust formulation of an insecticide like TriDie. Do not use this product as a broadcast treatment in areas where it may contact people.
  • Liquid or dust insecticides may be applied directly to webs (this works especially well for black widow spiders).
  • Non-residual aerosol sprays can be used to spray directly onto spiders.
  • If an outside treatment for hobos is warranted, insecticide sprays are best timed for when egg sacs are hatching, which is typically from mid May to mid June in northern Utah.

Bite Prevention Tips

  • From August through October, remove skirts on beds and pull the bed about 8 inches from the walls to prevent wandering spiders from climbing the bed.
  • Take caution when picking clothes up off the floor or in laundry baskets. Spiders hiding in these clothes can be mistakenly grabbed, resulting in a bite.
  • Keep children’s toys off of the floor where spiders can hide under them.

For more information on common Utah spiders, visit our Top 20 Arachnids web page.

-Ryan Davis, Arthropod Diagnostician  


Featured Picture of the Quarter

Late blight, caused by Phytophthora infestans, is a devastating disease of tomato and potato that occurs worldwide. It can wipe out an entire field in days because each small lesion can produce 100,000-300,000 spore-carrying structures to create new infections. We rarely see late blight in Utah because this pathogen needs moisture to spread; in fact, it was only first recorded in the UPPDL database in 2005. This year, however, the diagnostic clinic has seen several cases, which is not surprising given the increase in moisture Utah has received in the last 3 years.

-Image by the UPPDL