Weather

May has been warmer and drier

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May 2015 is half over and it is time to see how the monthly climate is doing so far.  The maps from the High Plains Regional Climate Center below show that for the region as a whole, temperatures are running about 1.5 degrees above the 1981-2010 normal, while the precipitation is much below normal and in some areas none has fallen at all, which is shown on the “percent of normal precipitation” map as an area of dark red, indicating zero percent of normal rainfall for the month.  Atlanta broke their record for the driest start to May before finally getting rain on 5/17.  Athens, GA is the driest May to date on record and Macon is tied for the driest, although rain is likely at both locations this week.

pct-normal-precip-may-2015-5-18-2015

For the rest of the month, warmer than normal temperatures are expected to continue.  Rainfall is expected to increase and may even be above normal for the rest of the month, although it will be spotty.

Dealing with freeze injury to ornamental plants

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Jean Williams-Woodward, Extension Plant Pathologist

Freeze injury symptoms can include blackening or bleaching of foliage, tip dieback, stem or branch splitting, and plant death. The damage may not be readily apparent, especially on trees. Trunk damage and splitting may develop months to years later.

Often weak pathogens invade the damaged tissues resulting in trunk and branch cankers (usually from Botryosphaeria spp. infection) and secondary infection by weak pathogens, such as Colletotrichum spp. and Pestalotiopsis spp.

The best approach to deal with freeze injured tissues is to prune off the affected tissues. Prune dead branch tips after bud break. Give plants, such as liriope, a shearing to remove dead foliage.

Freeze on boxwood Woodward

Freeze on cast iron plant Woodward

 

 

 

 

 

 

 

 

 

 

Freeze injury symptoms of bleached, necrotic foliage and split bark (seen at arrows) on boxwood (left), cast-iron plant (upper right) and holly (bottom right). (Images of holly and cast-iron plant by Jean Williams-Woodward; Image of boxwood by Greg Bowman, Gordon County Extension Coordinator)

Severe weather chances increase as we move into spring

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Taken from the CASE website

Now that spring is here and warmer, more humid air is entering the US, severe weather and tornado chances are increasing across the country.  There is an excellent animation that shows how the region of severe weather occurrence moves around the country at the NOAA Storm Prediction Center.   The area of most likely severe weather moves north and south with the area of greatest temperature contrast and most active storm track as the sun’s angle changes over time.

The Weather Channel has also provided a series of bar graphs which show the monthly probability of tornadoes for over 40 cities around the country (link).  From the graphs you can see that the Southeast has a split severe weather season, with the major peak in spring and a secondary peak in late fall.

For answers to every question you can ask about tornadoes, check out the tornado FAQ from the Storm Prediction Center.

And make sure you have access to real-time severe weather warnings via smartphone app or NOAA weather radio, especially if you are working outside on high-risk days.

 

severe-prob-3-16-2015-from-spcATL-tornado-by-month-TWC 

When do we expect the last frost?

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Taken from the CASE website and written by Pam Knox, University of Georgia Agricultural Climatologist

Now that March is upon us and the atmospheric pattern has shifted into something that is bringing more spring-like weather to the Southeast, it’s time to think about planting.  And that means thinking about the last frost of the winter.

AgroClimate has a tool which shows the last frost date by county for the Southeast.  The 50 percent map shows the average date for the last frost, while the 10 percent map shows the date that one in ten years will see a frost, and the 90 percent map shows the date for which in just one out of ten years the last frost will come early (or in other words, in 9 out of 10 years the last frost will come later than this date).  The maps below show the dates for 32 F.  You can find the tool athttp://agroclimate.org/tools/Freeze-Risk-Probabilities/.



   

If you need the information for a different temperature threshold, then a good source of information is the Southeast Regional Climate Center.  You can go to their web page www.sercc.com and pick “Historical Climate Summaries” from the “Climate Data” menu at the top.  Pick your station and then look for “Spring Freeze Probabilities” on the left menu.  Here is the graphical output for Tifton, GA.

tifton-spring-freeze-probabilities-sercc

What this shows is that for Tifton, for a temperature of 32 F (orange line) at the 50th percentile (for the average date), the date is about March 10.  You can click on the link for tabular data to get a table of numbers instead of the graph shown here.  Keep in mind that this is for the period of record for the station, and that last dates for spring freeze have been trending earlier in the season in recent warm years.  If you have a different source of freeze information that you like to use, please let us know!

Success with Off-Season Sodding

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SodClint Waltz, Extension Turfgrass Specialist, University of Georgia. This info is edited from a longer article which can be read here.

Dormant transplanting of trees and ornamentals in the Southeastern United States is a common practice. Warm-season turfgrass sod can also be successfully established during dormancy.

Recommendations for normal sodding also apply to off-season sodding.

  • Successful transplanting is highly dependent on healthy sod, which is difficult to determine when the sod is dormant or overseeded.
  • Rootzone preparation is critical for success. Loosen the soil to a depth of 6 inches by tilling before sodding.
  • During site preparation prior to turf establishment is the best time to take a soil sample to determine pH and nutrient needs. Correction of soil pH and soil nutrient deficiencies is more effective when lime and fertilizer are incorporated into the soil before sodding.
  • Next, level smooth and moisten the soil. The soil should be lightly watered, but not saturated. Ruts from foot traffic or equipment can occur when soils are too wet and are difficult to repair after the sod is laid.
  • To prevent drying and potential cold injury of roots, install sod within 48 hours after harvest. This also allows the radiant heat from the earth to offer the sod some protection from cold injury when compared to turf exposed to the elements on a pallet.
  • Sod should be laid tight and rolled to minimize creases. If creases are apparent after sodding, top dress the sod to fill low spots, conserve moisture and potentially retain heat near the soil surface.
  • For best survival, avoid winter desiccation and low temperature injury. Dessication can be a significant problem since the warm dry winds of late winter and early spring increase the demand for water, but the combination of low soil temperatures and a limited root system will reduce the plant’s ability to obtain water.
  • Direct low temperature injury can be a problem because the crowns, stolons and shallow rhizomes may be killed. Unfortunately, newly sodded turf lacks deep rhizomes and the expansive root system necessary to recover from winter stresses.

Research and practical experience has shown that warm-season turfgrasses may be successfully sodded during the off-season (October-April) when the grass is dormant or slowly growing. However, the cooler climates in and north of Atlanta may damage some turf species. More winter injury has been observed on zoysiagrass and centipedegrass as compared to bermudagrass sodded in the fall or winter.

  • Overseeding sod with ryegrass may reduce warm season turf vigor and quality. While overseeded turf may look appealing during the winter months, during the spring the more heat-tolerant perennial ryegrasses can compete with the warm-season turf for water, nutrients and light. This can cause a poor spring transition and delayed green-up of the warm-season species. This is more common in ryegrass that has been heavily fertilized in the spring.
  • To assist spring green-up and stimulate turfgrass growth, fertilize with 1.0 to 1.5 pounds of nitrogen per 1000 square feet once night temperatures consistently reach the mid 60s F. Also to further encourage warm-season species growth, lower the mowing height. This practice opens the turfgrass canopy, allowing more sun to the permanent warm-season species while stressing the overseeded grass. Resume accepted maintenance practices once conditions are favorable for warm-season turfgrass growth.

In summary, successful sod transplanting depends on proper soil preparation, good soil-to-sod contact, avoiding low temperature injury, and most importantly – proper water management to prevent desiccation. For more information, see these resources or contact your local UGA Extension Office.

See the original article here which has more information

Lawns in Georgia

Protect landscape plants from winter temperatures

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Frank Watson is the University of Georgia Extension Agent in Wilkes County

Landscape plants get plenty of attention during the summer, but they need protection during Georgia’s winter months. Rather than trying to keep plants warm, gardeners should help protect plants from wind, snow, ice, drastic soil temperature changes and heat from the sun on cold days.

Reducing water loss can protect evergreen plants. All plants transpire, or lose, water through their leaves. Evergreens continue to lose water during the winter, so the plant’s roots must be able take up moisture.

Homeowners are more conscious of watering shrubs during the summer and often neglect to water plants during cold weather. Roots absorb moisture when it’s available, but during a dry period or even when the ground is frozen, moisture isn’t available. The plants continue to transpire water, drawing moisture from living cells. If too much water is released, the plant’s cells die, causing the plant’s leaves to turn brown and die.

High winds and warm sunshine on cold days result in a higher rate of water transpiration. Protection can be offered by relocating susceptible plants to a sheltered location. Also, provide them additional water during dry periods or prior to expected hard freezes.

An additional layer of mulch is also recommended during winter months after the first freeze. Mulch will reduce water loss from the soil, aid in transpiration and reduce “heaving” of the soil as the ground freezes and thaws. Soil heaving, or frost heaving, occurs when soil swells during freezing conditions and ice grows towards the soil’s surface.

To protect plants from cold damage, University of Georgia Extension horticulturists recommend following these six steps:

  • Plant only varieties that are hardy for the area. Buy plants using the USDA hardiness zones.
  • Given a choice, plant less-hardy plants in the highest part of the landscape. Cold air settles in the lowest area.
  • Protect plants from cold wind with a fence or a tall evergreen hedge of trees or shrubs.
  • Shade plants from direct winter sun, especially early morning sunshine. Plants that freeze slowly and thaw slowly will be damaged the least. The south side of the house, where there is no shade, is the worse place to plant tender plants.
  • Stop feeding plants quickly available nitrogen in late summer to allow them to “harden off” before cold weather arrives.
  • Plastic covering provides excellent protection. Build a frame over the plant or plants, cover them with plastic and secure the plastic to the ground with soil. Shade plastic to keep temperatures from building up inside. Plastic traps moisture and warm air as it radiates from the soil and blocks cold winds. Do not allow the plastic to touch plants.

For more information on how to care for ornamental plants in the winter, see the UGA circular Winter Protection of Ornamental Plants.

 

Preparing Nursery Plants for Winter in the Southeastern United States

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A new publication from UGA and other southeastern universities equips nursery workers (and others) to protect container and dug plants from freezing temperatures. The publication explains winter acclimatization and how cultural practices (pruning, watering, fertilization, etc.) can impact cold hardiness. The publication also discusses the types of winter injury and methods to protect plants from winter temperatures.

Find the publication online here.

The following is a brief list of some of the Strategies and Techniques to Protect Plants

  1. Push pots together in large blocks.
    1. Wrap outside edge of plants with microfoam, spunbond nonwoven polyester material, or pine straw bales to protect from wind. No protection on inside containers.
    2. Mulch in and around plants on the inside of the block using:
      i. Newspaperwinter protection
      ii. Pine straw, hay, or some other grain
      iii. Leaves or other composted material
    3. Cover blocks of plants with microfoam or spunbond nonwoven polyester fabric.
      i. Cover fabric with white polyethylene.
      ii. Use mulches under the fabric.
  2. Overwinter plants inside a quonset-style greenhouse or similar structure.
    1. Place single-layer white poly cover on house.
      i. Push plants close together with no further protection.
      ii. Cover plants inside structure with microfoam or spunbond nonwoven polyester.
      iii. Heal plants in with mulch.
    2. Place double-layer white poly cover on house with inflator fan to create an insulating dead-air space between plastic covers.
      i. Also cover plants with microfoam or spunbond nonwoven polyester.
      ii. Provide an independent heat source inside the house:

      1. Portable forced-air heater that runs on fuel or electricity
      2. Permanent propane, electric, or wood-fired heater

Note: Organization of ideas based on Dunwell and McNeill, 2009.

What happens to West Nile Virus in the winter?

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Where, oh where, does the virus go (in the winter)?

Dr. Rosmarie Kelly, Public Health Entomologist, Georgia Department of Public Health

It’s that time of year when those in mosquito surveillance and control think fondly of consistently cooler temperatures and eagerly await that first hard frost. Of course, this is already happening in some places up north. We may have to wait a while longer in here in Georgia. But that does bring to mind the question: Where do all the mosquitoes go once the colder weather arrives?

Mosquitoes, like all insects, are cold-blooded creatures. As a result, they are incapable of regulating body heat and their temperature is essentially the same as their surroundings. Mosquitoes function best at 80 F, become lethargic at 60 F, and cannot function below 50 F. In tropical areas, mosquitoes are active year round. In temperate climates, mosquitoes become inactive with the onset of cool weather and enter diapause (hibernation) to live through the winter. Diapause induction also requires a day length shorter than 12 hours light (more than 12 hours dark). All mosquitoes pass through four developmental stages: egg, larva, pupa and adult, and diapause can occur in any of these stages depending on the species.

  • The Aedes and Ochlerotatus species, and some Culiseta species, lay eggs in dry or damp, low-lying areas or containers that are subject to flooding from accumulations of precipitation. Winter is passed in the egg stage, with hatching dependent on the presence of water, water temperature, and amounts of dissolved oxygen.
  • Coquillettidia and Mansonia species, and some Culiseta species, have larval stages that overwinter, apparently without total loss of activity, restricting development to very permanent water bodies. These species renew development towards the adult stage once water temperatures begin to rise.
  • Overwintering in Anopheles, Culex and some Culiseta species takes place in the adult stage by fertilized, non-blood-fed females. In general, these mosquitoes hide in cool, dark places waiting for temperatures to rise and days to lengthen before they seek out a blood meal and resume their lives.

What, if anything, does this mean for West Nile virus (WNV)? If the mosquitoes are infected with WNV when they enter diapause, it should overwinter with them to be transmitted to birds when the mosquitoes emerge the following spring. Temperature is the crucial factor in the amplification of the virus. Studies in various states have shown that WNV does indeed overwinter in mosquitoes. The virus does not replicate within the mosquito at lower temperatures, but is available to begin replication when temperatures increase. This corresponds with the beginning of the nesting period of birds and the presence of young birds. Circulation of virus in the bird populations allows the virus to amplify until sufficient virus is present in the mosquito populations (and vector mosquito populations are high enough) that horse and human infections begin to be detected.

In the Northeastern U.S., Culex pipiens, the northern house mosquito, is the most important vector species. This species overwinters as an adult, and has been found harboring WNV during the winter months. This mosquito goes into physiological diapauses (akin to hibernation) during the winter months, and while it may be active when temperatures get above 50°, it will not take a blood meal.

Culex quinquefasciatus, the southern house mosquito and the major vector for WNV in Georgia, also overwinters as an adult, and also goes into diapause when winter comes, and it is likely that this mosquito also harbors WNV throughout the winter months.  However, the southern house mosquitoes go into more of a behavioral diapause when temperatures are below 50°, and are quite capable of taking a blood meal (and maybe transmitting WNV) when things warm up during the winter, which is not an unlikely occurrence here in Georgia especially as one goes further south. So, although the risk for WNV transmission in the south in the winter months is very low, it is certainly possible.

City Heat Boosts Tree-Killing Scale Insect Populations

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A red maple branch heavily infested with gloomy scales (identified by the small bumps covering the bark).
A red maple branch heavily infested with gloomy scales (identified by the small bumps covering the bark).

From Entomology Today

Big cities with large expanses of concrete, asphalt, and buildings are usually warmer than the suburbs or countrysides that surround them, a phenomenon known as the urban heat island effect. Now new research from North Carolina State University shows that these urban heat islands increase the number of young produced by the gloomy scale insect — a significant tree pest — by 300 percent, which in turn leads to 200 times more adult gloomy scales on urban trees.

Read the original article here

Lawn and Garden Moisture Index

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Information taken from the Climate and Agriculture in the Southeast (CASE) newsletter.

Do things seem really dry where you are?  How much should you water your lawn or irrigate your crops?  There are a number of commercial products out there that can help you determine this, but one simple method that is available for free is the Lawn and Garden Moisture Index, a daily map put out by the Alabama State Climatologist based on estimated rainfall from radar.  This map tells you whether your lawn and garden have enough moisture or if more needs to be added.  This is one of a number of useful products available on AgroClimate.org, a website developed by the Southeast Climate Consortium, a group of eight universities around the Southeast.

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This map shows the areas with surplus water in greens (no need to water or irrigate there) and areas with a water deficit in oranges and reds.  The darkest red areas are almost 2 inches short of water, including a large portion of Georgia.  If this situation continues, then the Drought Monitor is likely to add D0, abnormally dry conditions, to the next weekly Drought Monitor map.  Areas with deficits of an inch or more should be irrigated to help alleviate the dry conditions and keep lawns and gardens healthy.

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