K-State Research and Extension News
June 28, 2012
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Bagworms’ 2012 Control Window Closing

Is a Heat Wave Truly Hot?

Hot Weather Triggers Heat-Stress Trilogy

Bagworms’ 2012 Control Window Closing


MANHATTAN, Kan. – The bagworm hatch began weeks early this year, due to spring’s atypically warm weather. Homeowners should act now to treat infested plants.

The younger the larvae, the easier they are to control, explained Bob Bauernfeind, K-State Research and Extension entomologist.


The worms’ youthful size is just one reason that’s true. At 1 millimeter long, new larvae are almost undetectable. They have lots of growing to do.


Even so, they don’t chow down as soon as they hatch. Instead, the larvae spin a protective silk bag around their body -- leaving strategic holes for eating, pooping and slo-o-owly walking.


“Bagworms are all about defense,” Bauernfeind said. “This year’s crop has grown enough that if you’re patient and focused, you can see them without a magnifying glass. They’re sort of hiding in plain sight, though. They’ve already started to ‘decorate’ their gradually expanding bag with bits and pieces of foliage.


“As those ‘decorations’ dry out, the bag becomes a bristly brown. It also becomes increasingly hard to penetrate with sprays.”


Unfortunately, that’s the point at which many homeowners begin to notice bagworm damage. And, when larvae are big enough to eat that much, their protective cover is almost complete.


“This year, they could be closing themselves in for further development by early August,” Bauernfeind said.  


Hurried treatments won’t provide good control, even while larvae are small. Sprays must be thorough, from branch tip to trunk and from top to bottom, he warned. Reaching the inside, as well as the outside foliage takes time and may require refilling spray equipment.


Many labeled products will reduce bagworm numbers, Bauernfeind added. Organic options (most effective on young larvae) include Bacillus thuringiensis and spinosid. Popular chemical controls’ labels list such active ingredients as acephate, bifenthrin, carbaryl, cyfluthrin, cyhalothrin, malathion, or permethrin.





Is a Heat Wave Truly Hot?

MANHATTAN, Kan. – When does hot weather become a heat wave?

Some experts believe daily low temperatures should set the threshold.

“They point to several studies that found an increase in heat-related illnesses and deaths when daily low temperatures remained above 75 degrees. That finding held true, regardless of how extreme the high temperatures were,” said Mary Knapp, State of Kansas climatologist, based with K-State Research and Extension.

In comparison, the National Weather Service definition for “heat wave” is vague: “A period of abnormally and uncomfortably hot and unusually humid weather.”

“The NWS can’t be more specific,” Knapp said. “The actual threshold varies from region to region. A heat wave in Boston could be nice weather for Miami.”

What’s not vague, however, is that hot weather can be deadly. It often leads the annual statistics for U.S. weather-related deaths, placing above hurricanes, tornadoes and floods, she said.

Besides, humidity worsens heat’s effects on the human body – a fact reported nationwide as Heat Index (“feels like”) temperatures.

Knapp said other dependable measures are the outlooks, watches and warnings the National Weather Service issues for excessive heat, just as it does for other extreme weather. Those bulletins immediately become top news.

When the NWS has issued a heat advisory or warning, for example, those classifications can specifically mean:

            * Consecutive days with a Heat Index of at least 105 F for three or more hours per day.

            * Consecutive days with nighttime lows above 80 degrees.

            * Any period of time with a Heat Index above 115 F.


Hot Weather Triggers Heat-Stress Trilogy

MANHATTAN, Kan. – Air temperatures above 100 degrees can trigger a human heat-stress trilogy:  heat cramps, heat exhaustion and heat stroke.

“Heat cramps are the mildest reaction. They occur when you don’t replace the salt or potassium lost in sweat,” said Mary Knapp, climatologist with the Kansas Weather Data Library.

Heat exhaustion is more severe, she said. It sometimes results when people engage in vigorous summertime activities (e.g. football, tennis, running, soccer).

Heat exhaustion means the body’s cooling system is overloaded, but hasn’t shut down. Symptoms can include heavy sweating (i.e., clammy skin), headache, dizziness, nausea, muscle cramps and fatigue.

“When people reach that point, you need to get them into a cooler location, lying down with their feet slightly elevated. Then try to lower their body temperature with cool, wet cloths. Give them water or an electrolyte drink. Monitor them for an hour to see that their symptoms improve, not worsen,” Knapp said.

The deadliest trilogy member is heat stroke: when the body’s cooling system has shut down – stopped. A defining symptom is 104-degree or higher body temperature.

“Heat stroke is a 911 situation. The risk increases along with the severity of symptoms and the length of delay in getting medical treatment.  Even if victims survive, untreated heatstroke can damage their brain, heart, kidneys and muscles,” Knapp warned.

Other symptoms include lack of sweat (unless exercise was involved), racing pulse, rapid breathing, flushed skin that’s hot and dry, vomiting, confusion, muscle malfunctions, seizures, and even unconsciousness.

“Heat stroke victims need help while waiting for the ambulance. Minutes count,” Knapp advised. “You can move them out of the sun. Put cold, wet towels or ice packs on their head, neck, armpits and groin. Remove excess clothing. Turn on a fan, mist them with water … do whatever you can, but quickly.”


K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by: Elaine Edwards
K-State Research & Extension News

Contributing writers: Mary Lou Peter and Kathleen Ward