Pest Control Alerts

Climate Outlook for 2014 Growing Season and Winter 2014-15

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Pam Knox, UGA Climatologist

Taken from Climate and Agriculture in the Southeast (CASE)

Following a very wet 2013, this year has gotten off to a drier than usual start, although generally soil moisture has been very good until recently. In the last few weeks, abnormally dry conditions have started to creep into the mountains in northeast Georgia as well as scattered locations in the west central and southwest parts of the state.  However, a major drought is not expected to develop this growing season.

Short-term forecasts out to two weeks indicate that some dryness may continue in southern Georgia but north Georgia is likely to be wetter. In the one to three month period that includes April through June, there are equal chances for below, near, and above normal rainfall, since accurate predictions are very hard in neutral conditions when no El Nino or La Nina are occurring. However, following recent climate trends, temperatures have an increased chance of above normal conditions for the next few months.

NOAA has now issued an El Nino watch for the potential development of an El Nino in the eastern Pacific Ocean by mid to late summer. When an El Nino occurs, we commonly see wet and cool conditions in south Georgia associated with the persistent presence of a subtropical jet stream above the earth’s surface which directs weather systems right across Georgia.

At this time, NOAA is predicting a 50 percent chance of an El Nino developing by midsummer.  If one does occur, then we can expect next winter to be cooler and wetter than normal in 2014-2015. Some scientists believe that this is likely to be a stronger than usual El Nino based on current ocean temperatures. If that happens, the cool and wet conditions will extend throughout Georgia instead of just affecting the southern part of the state.

One impact of El Nino on Georgia’s climate is a reduction in the number of hurricanes in the Atlantic Ocean. However, even in a quiet season, a single direct hit by a hurricane or tropical storm can cause significant damage to the area it passes over. Most other effects of El Nino are seen in the winter when the El Nino is strongest.

Other impacts from El Nino include excessive cloudiness, which reduces solar radiation and increases drying times for hay as well as enhancing the development of fungal diseases. Low-lying areas are likely to be soggy and hard to work due to the persistent rain. Cooler temperatures and high humidity may also affect the development of pecans and Vidalia onions, reducing pecan yields as well as the average size of the onions. In general, El Nino winters are not associated with unusually late frost dates, however.  Runoff may also increase, leading to increased erosion or movement of surface applications into streams.

You can find more information about the impacts of El Nino on climate patterns and crop yields at www.agroclimate.org.

Amended Rules of the Georgia Structural Pest Control Commission effective April 1

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GDA emblemA new webpage has been created to host the amended Rules of the Georgia Structural Pest Control Commission (SPCC) which became effective on April 1st.  The new page includes:

  • All chapters of the rules of the SPCC
  • The 2014 Residential Building Code (RBC) for under-floor ventilation
  • The rule implementation, assistance & compliance timeline
  • Structural Pest Control Act of 1955 and
  • FIFRA.

The new page  named Laws and Regulations is found on the SPCC website and the Structural Pest Control Section webpage.  All licensees were notified of the proposed rule changes in October 2013.  Based on the comments received during the public comment period, the SPCC revised some of the proposed rules.  As part of our outreach and compliance assistance effort, this announcement  was sent to all licensee email addresses that we have currently on file.

The SPCC is currently working closely with the Georgia Department of Agriculture to develop guidance policies and fact sheets to assist the industry with compliance.  As these resources become available, they will be posted on the SPCC website under “Guidance Policies”.

Laws & Regulations webpage – http://www.agr.georgia.gov/laws-and-regulations.aspx

The Georgia Structural Pest Control Commission

Chris Gorecki, Chairman

Derrick Lastinger, Vice-chairman

Maurice Redmond, Georgia Department of Public Health

Dr. Brian Forschler, University of Georgia

Bodine Sinyard, Adams Exterminating

Greg Holley, Zone Pest Solutions

Laurie Padgett, Consumer Protection Representative

Bees, wasps, and hornets take wing across Georgia

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The warmer temperatures are bringing out the bees! Here is some information on some common flying insects we are seeing. This information is taken from the publication Management of Insect Pests in and Around the Home by Daniel R. Suiter, Brian T. Forschler, Lisa M. Ames and E. Richard Hoebeke.

Bumble bees (Apidae: Bombus spp.):

Large, black bees (3/4 inch) with bright yellow hairs on the thorax and/or abdomen. Bees from the same colony are different sizes.

Habits:

Bumble bees are common inhabitants of gardens, where they are most commonly found visiting and pollinating flowers. Highly beneficial. Bumble bees are social, and live in a colony with nest mates. Like yellow jackets, colonies nest in the ground. When their nest is threatened, bumble bees can be aggressive and may sting.

Interventions:

If the nest is not a threat to the health and welfare of humans, leave it alone as bumble bees are excellent pollinators. If the nest must be eliminated, find the entrance and treat with a labeled insecticide formulated as an insecticidal dust or one of the various wasp and hornet aerosol sprays that shoot their contents up to 20 feet. For more information see University of Georgia Extension circular #782, Stinging andBiting Pests, at caes.uga.edu/publications.

Might be Confused With:

Carpenter bees, digger bees, yellow jackets.

Bees, wasps and hornets take wing across Georgia
Bumble bee

Large Carpenter bees (Apidae: Xylocopa virginica):

Large, black bees (3/4 inch). Appearance similar to bumble bees but with naked, hairless abdomen. Abdomen black to blackish blue.

Habits:

In Georgia, March-May this bee can be found chewing dime sized holes in wood boards, logs, etc. It does not eat wood, but chews galleries to create a nest site where eggs are laid. Some bees (males) appear aggressive. Cedar boards are particularly susceptible to extensive damage by carpenter bees.

Interventions:

Apply an appropriately labeled dust, liquid spray, or jet aerosol directly into carpenter bee holes while bees are active. Begin treatment when bees are first found, and re-treat as needed. In late Summer, when all bees have left their nest sites, fill holes with wood filler, sand, and paint (or apply a quality wood finish).

Might Be Confused With:

Bumble bees.

  Bees, wasps and hornets take wing across Georgia

Digger bees (Apidae: Anthophora spp.):

One common species is a gray-colored bee closely resembling the honey bee, 1/2 to 5/8 inch. Females slightly larger than males.

Habits:

In the Spring (March and April), this otherwise solitary bee aggregates, often in large numbers, for the purpose of mating and reproduction. Typical aggregation/nest sites are barren, grassless ground. When numerous, dozens to hundreds (even thousands) of bees can be seen flying in an erratic fashion approximately one foot above the ground. Bees are beneficial pollinators, and not aggressive even at their nest site.

Interventions:

Digger bees are harmless, and killing them is not recommended. To discourage future nest-site aggregations, barren areas should be covered with mulch or new turfgrass should be planted. Irrigating the area on successive days may cause bees to abandon the location. If desired, apply a spot treatment to aggregation sites with an appropriately labeled residual spray.

Might Be Confused With:

Honey bees.

 Bees, wasps and hornets take wing across Georgia

Honey bees (including Africanized honey bee) (Apidae: Apis mellifera):

Caramel-colored, 1/2 to 5/8 inch, hairy bee sometimes with large accumulations of yellow pollen on their hind legs. Commonly found in gardens visiting flowers while collecting nectar. Africanized honey bees can be differentiated from non-Africanized honey bees only by a professional entomologist.

Habits:

Honey bees are one of the best known, most recognized and beneficial of all insects. They pollinate billions of dollars worth of crops each year. The Africanized honey bee, a more aggressive and potentially dangerous honey bee, was found in Georgia in 2010.

Interventions:

The most common problem associated with honey bees is that they sometimes nest inside walls of structures. Do not kill these nests, but call a professional beekeeper or pest management specialist because the bees and honeycomb must be completely removed. Find a beekeeper to remove the bees, then hire someone to remove the honeycomb and replace the wall. All honey bee material and honeycomb residue must be completely removed or secondary pest problems may arise. A carpenter’s skills are often needed. For more detailed information see University of Georgia Extension circulars #824, Honey Bee Swarms and Bees in Walls, and #782, Stinging and Biting Pests, at caes.uga.edu/publications.

Might Be Confused With:

yellow jackets, digger bees.

  Bees, wasps and hornets take wing across Georgia

Hornets (Vespidae: Vespa spp.):

The European hornet, Vespa crabro, was accidentally introduced into North America about the middle of the 19th century. It is a large eusocial wasp with the wings reddish orange and the petiolate abdomen brown and yellow striped. There are no native hornets in the U.S.

Habits:

European hornets build large, above-ground nests, usually in trees. Similar to yellow jackets and paper wasps, European hornets build a new nest each year. Each Fall all hornets die, with the exception of several queens, which overwinter. The following Spring these overwintered, mated queens initiate the construction of a new nest. European hornets are attracted to lights at night. They are not attracted to human foods and food wastes, as are yellow jackets, but they can damage fruits, such as apples, while the fruit is still on the tree.

Interventions:

If European hornets are found around the house at night, because these wasps will forage after dark and are attracted to lights, examine and change the lighting regime. Do not attempt to remove or treat a nest; call a pest management professional to remove nests near areas of human habitation or activity. For more information see University of Georgia Extension circular #782, Stinging and Biting Pests, at caes.uga.edu/publications.

Might Be Confused With:

Cicada killers, yellow jackets.

  Bees, wasps and hornets take wing across Georgia

Mud Daubers (Sphecidae and Crabronidae: many species):

Long, slender, solitary wasps 1 to 1.5 inches, with long, slender waists. Commonly glossy black or blue, some species with yellow highlights.

Habits:

Builds series of four- to six-inch long vertical mud tubes on walls in areas protected from rain and adverse weather. Commonly found under eaves, decks, etc. Each tube comprised of individual cells housing a single larva and spider prey that wasp larvae feed on.

Interventions:

Knock down dry mud nests with a broom and wash mud from wall with soap and water. For more information see University of Georgia Extension circular #782, Stinging and Biting Pests, at www.caes.uga.edu/publications.

Might Be Confused With:

Paper wasps, potter wasps.

  Bees, wasps and hornets take wing across Georgia

Paper wasps (Vespidae: Polistes spp.):

Large (1 inch), aggressive wasps when at their nest. Various species, but all build paper-like, multi-celled, inverted umbrella nests under rain- and wind-protected eaves where wasps can enter and exit easily.

Habits:

Each Fall all wasps die, with the exception of several queens, which overwinter in an inactive form in a well-protected, secluded environment such as under and in fallen logs and other ground debris. The following Spring, queens initiate and build a small paper nest where they lay eggs. Paper wasps build a new nest each year. Colonies grow and reach peak size in the Fall, at which time the cycle repeats. Like other social bees and wasps, paper wasps are aggressive when protecting their nest, and may inflict a painful sting in its defense. Adult wasps are excellent predators in vegetable gardens, and are more docile when not protecting their nest.

Interventions:

If nests are out of the way, leave wasps alone as they are highly beneficial predators. If desired, spray nest and wasps directly with an aerosol jet spray, or early in the year, before the nest contains too many adult wasps consider knocking down the nest with a long stick but be prepared – and able – to quickly flee the area as the nest is dislodged. Make certain no one in the area is allergic to wasp venom (stings). For more information see University of Georgia Extension circular #782, Stinging and Biting Pests, at www.caes.uga.edu/publications.

Might Be Confused With:

Mud daubers.

  Bees, wasps and hornets take wing across Georgia

Potter wasps (Vespidae, but sometimes recognized as Eumenidae: many species):

Also referred to as mason wasps. Common species dark blue or black with yellow or white highlights on abdomen and/or thorax. Solitary. Common species 3/4 to 1inch. Strongly sclerotized.

Habits:

This wasp builds characteristic, oval-shaped (1/2 to 5/8 inch diameter) nests that appear pot-like with a knob-like handle. Pots are ornate and constructed of mud, as if built by a mason.

Interventions:

Knock down ‘mud pot’ nests with a broom and wash mud from wall with soap and water.

Might Be Confused With:

Mud daubers.

  Bees, wasps and hornets take wing across Georgia

 

Spring & fall are good times to control fire ants!

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Original story by Sarah Lewis, student writer with the UGA College of Agricultural and Environmental Sciences

“April and September are good times to apply baits, once at the start of the season and toward the end to help control before they come back in the spring,” said Will Hudson, a professor with the UGA College of Agricultural and Environmental Sciences.

Fire ants are most active in warm weather. Fire ant season can last 10 to 11 months out of the year in the most southern areas of Georgia. Controlling ant colonies before they produce a mound is important. However, Hudson says that once a treatment program is in effect, timing is not all that important.

Baits and sprays

The general rule of thumb is if the area is one acre or less, don’t use baits. Re-infestation is more likely from colonies outside of the yard when baits are used.

One important thing to remember is the difference between ‘no mounds’ and ‘no ants.’ “There is a difference between eliminating ants and controlling them,” he said. “Baits do not eliminate ants because there is no residual control. A new colony can still come in and be unaffected by the bait laid down prior to their arrival.”

To eliminate mounds completely, apply baits every six months, Hudson said. “There will be invasion in the meantime, and you will still have fire ants, just not enough to create a new mound,” he said.

Hudson recommends treating lawns smaller than an acre with a registered insecticide in a liquid solution. This should rid the lawn of fire ants for one to three months. If you choose a granular product, measure carefully to be sure you apply the correct amount of material and get good, even coverage, he said.

The least effective treatment option for most people is individual mound treatments, according to Hudson. Treating mounds in general is going to be an exercise of frustration, and killing an entire colony by treating just the mound is a challenge, he said.

Minimal impact

Baits are considered to have minimal environmental effects for those who chose not to use hazardous chemicals. Once the bait is out, there is hardly anytime for anything to come in contact with it before the ants get to it.

Nonchemical options include using steam or boiling water. “We recommend using boiling water to treat a mound near an area such as a well where you do not want any chemicals,” Hudson said. “Using hot water is very effective, but the problem is you are not always able to boil the water right next to the area you want treated.” Carrying the boiling water can inflict serious burns, so extreme caution should be used when treating with this method.

There are products on the market that are approved by the Environmental Protection Agency and labeled as organic. Hudson says organic designation is a “slippery” definition. There is an official USDA certification and many states have their own set of regulations when labeling a product as organic. This labeling can mean the product is either a natural product or derived from a natural product. “While there are a few products that qualify as organic, with most baits the actual amount of pesticide applied is minimal,” he said.

Realistic expectations

Hudson says to be careful when choosing a product because the labels can be confusing, even deceptive, and it is difficult to make the right choice. For assistance in selecting a product, contact your local UGA Cooperative Extension agent.

“The most important thing to remember is that you need to be realistic in your expectations,” Hudson said. “If you are treating mounds, you need to be prepared. You are going to chase the mounds around the yard.”

For more information on selecting a control measure:

UGA Pest Management Handbook

Fire Ant Control Materials

Managing Imported Fire Ants in Urban Areas

Winter near average for Georgia in spite of some cold mornings

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Pam Knox serves as University of Georgia Agricultural Climatologist with UGA Department of Crop and Soil Science

Released March 20, 2014. See original article here.

Despite some bone-chilling days with single digit lows, Georgia’s winter was about average in both temperature and precipitation.

This winter, which climatologists define as Dec. 1 to Feb. 28, was actually the 57th coldest out of the past 119 winter seasons. This means that 56 years were colder than the 2013-2014 winter season and 62 were warmer. This places it just about right in the middle.

Georgia’s winter precipitation was ranked 67th out of 119 years, which means that 66 years were drier and 52 were wetter.

The near-normal average temperatures this year were the result of a combination of the scattered days with above normal or record-high temperatures that some parts of the state experienced and the periods of frigid weather that brought very cold temperatures to northern parts of the state.

This was the first time that such cold temperatures have been observed in Georgia since the winter of 1995-1996. Periods of very cold weather were more frequent in the 20th century than in recent years.

The winter conditions provided plentiful chill hours for peaches across Georgia. The fruit should be in great shape as long as a late frost after blooming does not hurt the development of the peaches this spring.

Cold conditions have reduced the average size of Vidalia onions this year as well as cut stands by up to 25 percent. Overall, however, supplies are considered to be very good.

Lawns in north Georgia with warm-season grasses like centipede may see some damage due to some of the extreme low temperatures.

Some insect pests may have been cut back by the cold weather, but many are well adapted to shelter in the coldest conditions and the rapid swings in temperature may not have provided long enough cold conditions to cause a significant dent in their populations.

Other impacts from this winter’s weather include the damage to timber in the mid-February ice storm. The ice caused widespread power outages and tree damage to north central and eastern Georgia, particularly in the Augusta area.

While the state is starting to shake off the chill of the last few months, Georgians can expect cooler and wetter than normal conditions across Georgia for the next two weeks, based on predictions from the Climate Prediction Center, NOAA.

Gardeners should also remember that a late frost is still possible and perhaps more likely than in other years because the state is in a neutral weather pattern — one not affected by La Nina or El Nino.

New Urban Pest Management Webinar Series

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Come experience the future of training for Georgia’s pest management industry! The University of Georgia’s College of Agricultural and Environmental Sciences, powered by the Digital Innovation Group, has developed a training program that will allow pest management professionals to obtain re-certification and re-registration credit on-line, in the comfort of their home or office.

All your computer will need is the ability to access the internet. No special software is needed on your part. Logging on, watching a live online presentation (called a webinar), and then going back to work is just a few mouse clicks away. No more long drives and time off work to acquire credits!

Mark your calendar for the 2014 webinar series (all webinars 8:00 to 9:00 am).

April 16. Dr. Susan Jones, The Ohio State University on Bed Bug Monitoring
June 18. Mr. Elmer Gray, University of Georgia on Mosquito Biology
August 20. Dr. Brian Forschler, University of Georgia on Termite Biology
October 15. Dr. Karen Vail, University of Tennessee on Ant Pests of the Southeast
December 10. Dr. Ron Harrison, Orkin Technical Services on Bed Bug Control

How the Program Will Work. Several weeks prior to the event, Dr. Dan Suiter will announce the webinar by email. In the email will be instructions on how to register. If you’d like to be put on his mailing list, simply send an email to Dr. Suiter at dsuiter@uga.edu, and note that you’d like to be notified when registration for each webinar opens. Or, if you’d simply like to learn more about the series feel free to call Dan at 770-233-6114 to chat.

Hope to see you on-line February 19!
Dan Suiter, Ph.D.
Department of Entomology
College of Agricultural and Environmental Sciences
University of Georgia, Griffin Campus
1109 Experiment St, Griffin, GA 3022

Check out the UGA College of Agriculture & Environmental Sciences Social Media

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Social media CAES 2Do you like Facebook, Twitter, YouTube or blogs? If so, the UGA College of Agricultural and Environmental Sciences may have something of interest for you!

The college has a list of many of its social media sites all in one location! Visit this site to see a list of the College’s many social media or blog sites.

Examples of information you can find include:

  • Your local Extension Office Facebook site
  • Twitter account featuring new and revised college publications (and research articles)
  • Blogs (online articles) for the landscape, pest control, row crop, and greenhouse industries
  • The UGA Trial Gardens or Coastal Botanical Gardens Twitter sites
  • Facebook pages covering invasive species, forage production, the Griffin Research and Education Garden and more …

Check out the college’s list of social media sites today at http://extension.uga.edu/about/social-media/

UGA entomologist Nancy Hinkle receives regional 2014 Recognition Award in Urban Entomology

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Nancy HinkleThe Entomological Society of America’s Southeastern Branch presented University of Georgia entomologist Nancy Hinkle with its 2014 Recognition Award in Urban Entomology.

Hinkle, who has been a medical-veterinary entomologist at UGA since 2001, primarily works with insect pests that affect the poultry industry. But over her career she also has researched various insects that affect humans — from fleas to head lice to mosquitoes. Because of her interest in blood-sucking insects, Hinkle has become one of the nation’s leading experts on delusory parasitosis or imagined infestations.

“Dr. Hinkle’s primary responsibility is working with the poultry industry and with veterinary or medical entomology (research), but in this work she encounters a number of problems that affect our urban clientele,” said Wayne Gardner, a UGA professor of entomology with the College of Agricultural and Environmental Sciences. “Even though it’s not her primary responsibility, Dr. Hinkle works to address each of those problems brought to her, and she addresses them quite effectively.” Gardner nominated Hinkle for the award.

Hinkle is the fourth UGA CAES entomologist to receive this award. Ron Oetting (1990), Dan Suiter (2010) and Brian Forschler (2011) have also received this honor. As Southeastern Branch winner, Hinkle is eligible for the Entomological Society of America’s national Recognition Award in Urban Entomology, one of the most prestigious awards the society bestows.

Hinkle’s work with urban and agriculturally problematic pests is well respected, but her two decades working with delusory parasitosis created a name for the entomologist outside of the academic world.

Her interest in the subject started in the 1980s when her doctoral advisor at the University of Florida, flea researcher Phil Koehler, received a sample he did not have time to identify. He handed it off to Hinkle who spent hours trying to identify the insect. There was nothing there. With funding from the Florida Entomological Society, Hinkle found that it wasn’t uncommon for pest control operators and labs to be asked to solve imaginary pest infestations.

As an Extension entomologist, she often received — and still receives — calls from worried individuals who believe they are infested with an unknown skin parasite. This condition is sometimes found in people with no other sign of mental illness or substance abuse.

She summarized her experience with “invisible bugs” in the 2010 Annual Review of Entomology article, “Ekbom Syndrome: The Challenge of ‘Invisible Bug’ Infestations.” In 2011, Current Psychiatry Reports included her article, “Ekbom Syndrome: a delusional condition of ‘bugs in the skin’,” to help mental health professionals understand the condition.

“She’s kind of a focal point for professionals who work with people affected by this condition,” Gardner said. “She broke it down and talked about the different issues that can cause it.”

In addition to her work with human and animal ectoparasites and delusory ectoparasites, Hinkle maps the geographic range of brown recluse spiders in Georgia and illustrates how rare the feared spiders are in the state.

Hinkle is currently working on control methods for avian mites, pest flies and darkling beetles that carry salmonella and can transmit the bacteria among poultry flocks. In 2012, she received the Lifetime Achievement Award from the Livestock Insect Workers Conference for her work with poultry and cattle parasites and pests.

Since her interests span the worlds of veterinary, agricultural and urban pest problems, Hinkle frequently addresses pest management conferences around the country. She has made more than 300 presentations to pest control groups, including 22 state associations, the National Conference on Urban Entomology, the Purdue Pest Management Conference and the National Pest Management Association.

Hinkle received a bachelor’s degree and a master’s in medical entomology from Auburn University and a Ph.D. from the University of Florida. She taught at the University of California, Riverside, for nine years before joining the UGA Department of Entomology.

Landscapes may be more at risk of a late frost this year

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Merritt Melancon is a news editor with the UGA College of Agricultural and Environmental Sciences

The northern and southern halves of the state vary slightly, but Georgia’s last frost typically falls between mid March and mid April. On some years the last frost has hit as late as May. University of Georgia Extension climatologist Pam Knox believes the current neutral weather pattern — one not affected by La Nina or El Nino — could put Georgia at greater risk for one of these rogue late frosts.

There’s no way for a gardener to predict or stop a late frost from hitting after they’ve put in transplants or started counting sprouts, but they can be prepared, said Paul Thomas, a UGA Extension horticulturist. Since no one knows when a frosty night might hit, gardeners should have a frost tool kit and game plan ready.

“Buying or collecting frost reduction materials prior to the frost and pre-positioning them close to the plants you want to protect is very important,” Thomas said.

One of the most effective ways to shield plants from frost is to cover them with any of a wide variety of materials, from high quality frost–reduction fabric, to blankets and sheets, to newspapers, baskets and straw.

For small shrubs such as Gardenia, a supply of old comforters or heavy blankets — maybe purchased from a local thrift store — will allow you to protect your plants from that first frost without spending much money. Covering plants with a heavier blanket will protect them more than if they’re covered with a simple sheet, Thomas said.

In addition to blankets, simple mulches — like dead leaves or grain straw — are some of the best materials for protecting small plants and flowers. For smaller plants such as young vegetable starts, lighter weight material like pine straw works great if enough is placed over the plants.

Gardeners can completely bury their newly flowering shrubs or tender garden seedlings in either leaves or straw, and then uncover them after the weather warms back up. The flowers and seedlings will be fine, he said.

Never use plastic sheeting to cover plants because plastic can trap too much heat. When the day starts to warm up, the plants can actually cook or scorch under the covering. “By 10:00 a.m. you can have significant damage to grass and young plants due to how quickly it can heat up under that plastic,” Thomas said.

It’s best to cover plants before sunset to retain some of the heat that is trapped in the soil and remove the coverings in the morning just after sunrise to prevent the plants from being scorched. The exception would be if it’s cloudy, snowing or icy.

Thomas also recommends having a collection of wooden garden stakes on hand. Place the stakes throughout your vegetable patch in order to suspend blankets over tender seedlings or delicate flowers. The stakes will prevent snow or rain soaked blankets from crushing your plants, Thomas said.

Insects and Cold Weather

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Elmer Gray, University of Georgia, Entomology Department

With this winter’s unusually cold temperatures, the question of how these conditions affect insects is sure to arise. It is of little surprise that our native insects can usually withstand significant cold spells, particularly those insects that occur in the heart of winter. Insect fossils indicate that some forms of insects have been in existence for over 300 million years. As a result of their long history and widespread occurrence, insects are highly adaptable and routinely exist and thrive, despite extreme weather conditions. Vast regions of the northern-most latitudes are well known for their extraordinary mosquito and blackfly populations despite having extremely cold winter conditions.

The question then arises, how do insects survive such conditions? In short, insects survive in cold temperatures by adapting. Some insects, such as the Monarch Butterfly migrate to warmer areas. However, most insects use other techniques to survive the cold.

Vector of West Nile Virus

In temperate regions like Georgia, the shortening day length during the fall stimulates insects to prepare for the inevitable winter that follows. As a result, many insects overwinter in a particular life stage, such as eggs or larvae. Many mosquitoes overwinter in the egg stage, such as our common urban pest the Asian Tiger mosquito (Aedes albopictus), waiting for warmer temperatures and sufficient water levels to hatch in the spring. Another technique is to take advantage of protected areas, as do adult Culex mosquitoes overwintering in the underground storm drain systems. Other insects overwinter as larvae or pupae in the soil, protected from the most extreme temperatures. However, this still doesn’t answer how insects survive freezing temperatures, only to become active as warmer temperatures return.

All insects have a preferred range of temperatures at which they thrive. As the temperature drops below this range the insects become less active until they eventually cannot move. A gradual decline in temperatures, coupled with a shortening day length, serves to prepare an insect to tolerate freezing temperatures. Several factors are important to this tolerance.

The primary thing that an insect has to avoid is the formation ice crystals within their body. Ice crystals commonly form around some type of nucleus. As a result, overwintering insects commonly stop feeding so as to not have food material in their gut where ice crystals can form. This reduction in feeding will also result in a reduction in water intake.

A degree of desiccation increases the concentration of electrolytes in the insect hemolymph (blood) and tissues. In addition, insects that can tolerate the coldest of temperatures often convert glycogen to glycerol. These electrolytes and glycerol create a type of insect antifreeze. This will lower the freezing point of the insect to well below freezing, a condition described as supercooling. When this occurs, the insect can withstand extremely cold temperatures for extended periods.

However, at some point insects will suffer increased mortality, possibly due to desiccation, toxicity or starvation. Nevertheless, insects are well adapted to survive freezing temperatures, especially after a few 100 million years to perfect their systems. It is generally assumed that introduced pest insects from sub- and tropical areas would be more susceptible to extended cold spells, but depending on their ability to find local refuges and their numbers and adaptability, they likely will remain viable and persist as pests as well.

In summary, entomologists don’t expect the cold winter to have a significant impact on insect populations this spring. Local conditions related to moisture and overall seasonal temperatures (early spring/late spring) will play a much more important role in insect numbers as we move from winter to summer and prepare for the insects that will be sure to follow.

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