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The Pest Monitor

Volume 6, Number 3

                                                        September 1998

There is no workman, whatsoever he be,
That may both work well and hastily. Chaucer

Quiz Answered

    The question from the last issue dealt with rodents - what are the three rodents most likely to be encountered by the pest control professional? They are the house mouse, Mus musculus, Norway rat, Rattus norvegicus, and roof rat, Rattas rattas. Of these, the house mouse may generate the most complaints; however, over the last eight or nine months, I have received calls from two different towns concerning rats.

    All three belong to the order Rodentia consisting of the gnawing or nibbling mammals. These include, mice,squirrels, beavers, etc. which have large incisors adapted for the gnawing habit. The five skulls in figure one show from left to right the beaver, rat, mouse,  squirrel, and nutria - note the large incisors.                                                                                     

Click here for image. Fig. 1. Rodent skull showing large incisors.

    The term "commensal" separates rodents, such as rats and mice, from the other rodents in the group. Commensal means, "sharing a table" and over time rats and mice have gained certain advantages by associating themselves with humans. In this association, they have gained protection from predators, a source of food and nesting sites. The other rodents in the group have not formed this association, for whatever reason - it may be associated with size, specialized feeding habit or their habitat.

    It is sometimes hard to make generalized statements about a biological organism because they "don't always read the book" to find out how they are supposed to act. For example, a rodent, rat or mouse may act different in a single family dwelling than they would in a large warehouse. There are, however, some behavioral characteristics that seem to be fairly constant. These characteristics will be pointed out in the following discussions.

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Fig. 2.  The difference between the Roof and Norway rat are demonstrated, as well as a young rat and mouse.

    Mice. House mice are small and can enter buildings through openings very small. Due to their small size, they may also be carried into buildings in merchandise or in items that have been in storage. The house mouse is adaptable and can survive in outdoor situations as well as within buildings. Three behavioral characteristics common to mice are:

  • Curiosity. Mice are not alarmed when new items appear in their territory. In fact, they readily explore new items.
  • Feeding. Mice feed as nibblers. They tend to eat small amounts of a variety of foods (if available) over a 24 hour period rather than a few large meals.
  • Territory. Mice are territorial and may move within 20-foot radius, with the nest area being the focal point.

    Rats. The common commensal rats, Norway and roof rat, have different body characteristics as well as some behavioral differences - see figure two for the body differences. Either rat can be found within buildings, near food storage or preparation. How they enter buildings is a different matter. The Norway rat tends to enter at ground level from burrows that may be around the foundation base or in surrounding ditch banks or road right-of-ways. The roof rat, on the other hand, enters buildings from elevated points such as overhanging tree limbs or utility lines. Nesting sites for this rat tend to be located in trees or dense vine growth.

    Rats are totally different from the behavioral characteristics listed for mice:

  • Curiosity. Rats are not the least bit curious. In fact, they are highly suspicious of changes that occur within their territories, such as the addition of bait stations.
  • Feeding. Rats eat much more food at a single feeding than a mouse.
  • Territory. These animals have slightly larger territories than do mice. Once established, their territories may cover an area of approximately a 50-foot radius relative to the nest.

    Controls. Rodent control can be approached in the chemical mode that is similar to a "scorched earth policy." An area is baited with the hope the rat or mouse will stumble into the bait, eat it, and eventually die. Or one can do his or her homework (Inspection) and then bait according to what the animals are telling. During the inspection, look for the following:

  • Droppings. Fecal material is deposited daily by both rats and mice. A mouse may produce 50 to 100 droppings daily, while a rat will produce about 50 per day.
  • Tracks. These might be seen in crawl spaces or in dusty areas within buildings.
  • Gnaw Marks. Holes made by mice will be about 0.5 to one inch in diameter. Rats will be two inches or more in diameter.
  • Burrows. May be found around the foundation base.
  • Runways. Mouse runways can be seen in loose insulation in attics.
  • Urine Stains. These stains will fluoresce under UV light.

    During the inspection, entranceways into the building or poor sanitation might be discovered. If so, exclusion or improved sanitation could ultimately make your job much easier.

    Chemical/Non-Chemical Control Methods. Population reductions can be achieved using either trapping (non-chemical control) or rodenticides. Trapping (snap traps, multi-catch or glue boards) has some advantages that might be more acceptable in some situations than chemical control:

  • Safety. The possibility of accidental poisoning is eliminated.
  • Traps provide instant results.
  • Trapped rodents can be removed from the structure, eliminating odor problems.

    The disadvantage is labor, whether using snap traps, multi-catch or glue boards. These devices must be serviced frequently to eliminate trapped rodents. If they are not removed, odor along with customer complaints, will become a real concern.

    Be sure to use enough traps to cover the potential territory - with mice, more traps will be needed due to reduced territory.

    A number of categories can be used to separate the various rodenticides that are currently on the market. Three categories are first generation anticoagulants (FGA), second-generation anticoagulants (SGA), and non-anticoagulants (NA).

  1. FGAs - Rodenticides in this category include such compounds as chlorophacinone (Rozol, Eaton's AC 90) and diphacinone (Ditrac, Ramik Green). These materials are generally referred to as multi-dose" or "multi-feeding" anticoagulants. Materials in this category must be continually available to the rodent until a toxic dose is ingested.  Remember it will probably take more placements for mice due to their "nibbling" habit.
  2. SGAs - This group contains brodifacoum (Talon), bromadiolone (Contrac, Macki), and difethialone (Generation). Products in this category are referred to as "single-dose" materials.  Consequently, the rodent consumes a toxic dose much quicker.
  3. NAs -  Active ingredients in this category include bromethalin (Vengence) and cholecalciferol (Quintox). Bromethalin interrupts the production of energy in the cell and once a toxic dose is consumed, the rodent stops feeding.

    Rodenticides are produced in a number of formulations, including paraffin blocks, paraffinized pellets, meal, pellets, bait packs. There should be a formulation for any situation.

    When placing rodenticide bait -- and the emphasis is on placing and not throwing -- be careful. Most labels will specify the use of tamper resistant stations (Fig. 3). The industry has a good safety record in the use of rodenticides, and I would think everyone would want to keep it that way.

Crickets

    Fall and other things besides rodents are moving into the house - crickets are making their presence known. Most areas of the state are experiencing some problems; however, the western areas seem to have the highest populations. In these areas, crickets are congregating in very high numbers around storefronts, at street corners, and at any other brightly-lighted area.

 

Click here for image. Fig. 3.  Tamper Resistant Bait Stations

    This is unusual; however, it's not the first time it has happened. High populations were reported in 1951 and 1952 (Hutchins and Langston, Jour. Econ. Entomol., Feb. 1953). In 1951 cricket populations were extremely high in Greenville, and in 1952 the problem spread. Greenville, Starkville, Greenwood, Macon and Columbus all reported high populations in the fall of 1952. The problem from these years was described in the following manner. "They (crickets) seemed to be attracted particularly to neon light around the theatre and other establishments. It was reported that many sidewalks, particularly under street lights, were black with the crawling mass of crickets."

    It was speculated that these outbreaks were related to drought during this period. Dry weather may have reduced the incidence of disease in the cricket population, or the lack of rain may have allowed more young crickets to survive.

    The conditions which were present during '51 and '52 are the same that have been present in Mississippi during 1998. If crickets are occurring by the thousands, insecticide applications are going to be next to useless, particularly with lights acting as an attractant. I would expect the problem to last for three to four weeks.

    If you are dealing with a situation where a few crickets are showing up, a perimeter treatment would be in order. Any product with a perimeter statement on the label could be used. Keep in mind that this will not control any crickets that might already be in the wall void.

Firewood and Plants

    As we approach a cooler season, people will begin bringing plants and firewood into the house. A variety of insects could possible enter with these items. The flower pot soil might contain millipedes, ants, or sow bugs. Insects found under the bark in firewood might include wood roaches, ground beetles, flat-headed wood boring beetles, ants or flies. These insects will eventually move into the room resulting in calls from nervous clients who are worried that they are about to be covered up with critters.   

    You might want to warn clients about this possibility ahead of time. It might save a trip. This could be done during regular service calls over the next two months, or develop a door hanger which would alert the client about these insects. Suggest that they inspect pots and firewood before bringing it into the house. If any insects or other arthropods are found, they could be remove outside. Flowers might be treated by the client if it is deemed necessary; however, I would not treat firewood.

The Selling of Sentricon

    Dow Agro Sciences is currently circulating literature to their "authorized representatives" concerning Sentricon that seems a little askew. In the opening statements, they refer to termites; however, on subsequent pages of the literature, the termite that gets the largest print is the Formosan subterranean termite. For example, "Formosan Termites Could be a few bites away from Your Property" or "Nothings worse than Formosan termites" or "Hard on Formosans, easy on your property." These statements are true as far as it goes, but the Formosan termite is not wide spread in Mississippi or in the nation. It has been found in the three coast counties, plus Lamar, Forrest, and Pearl River counties. One infestation each has been found in Rankin and Lauderdale counties. Therefore, the question that begs to be asked is "Why send this literature to 'authorized representatives' outside of the area where Formosans have been found in substantial infestations?" It would appear that the literature wanted to maximize the fear potential. I have no problem with the active ingredient in this system; however, I think it could be marketed on its own merits and not on the potential of what might or might not be present.

Quiz

Describe what has happened in the following picture:

Click here for image.

 

James H. Jarratt
Extension Entomologist


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