The Drought Diaries: Insects

By Eilene Lyon

Mosquitoes

July 10, 2017

Today was my turn to walk the dogs. The Sarah-Palin-bugs (“Drill, baby, drill!”) were out in full force. By the time I got home, the back of my legs looked like West Texas. I almost wanted to jump in the ditch with the dogs.

Despite essentially no rain for seven weeks prior to this entry, the mosquitoes were the worst I can ever recall. Old-timers in the north valley (we live in the much drier south valley) can tell you how they used to go out in the fields and if they put a hand on a horse or cow, the entire hand would be smeared with blood.

Then the mosquito control districts were formed. For many years, exceptionally nasty chemicals such as Malathion were used. Effective, but highly toxic, it was phased out in favor of permethrin. Found naturally in chrysanthemums, this compound causes muscle spasms and paralysis, killing mosquitoes (and probably other insects as well).

Permethrin is also used on clothing and mosquito-netting to help fight malaria, Zika virus, and West Nile virus around the world.

However, the chemical used by the control districts is only part permethrin. It includes a brew that can cause health issues in humans and animals if inhaled, ingested or applied to skin. So, as with Malathion a generation ago, residents have begun campaigns to end its use.

But fighting adult mosquitoes is probably not the most efficacious approach to mosquito control. Killing larvae is better. Fish can eat a lot of larvae, so stocking ponds with mosquito fish is an option. There are also chemical treatments, but those can have unintended consequences. Ponds aren’t necessarily the problem, though.

Why would drought cause an increase in mosquito populations? Possibly because evaporation caused many water sources to dry up, leaving patches of puddles where mosquitoes love to lay eggs. These breeding grounds are difficult to treat, because they can be hard to locate.

Though I am generally in favor of preventing extinction, mosquitoes are one insect I would not miss if they were wiped from the face of the earth. I don’t know of any animal that depends solely on them for survival, though there are certainly disease agents that would be wiped out – oh darn.

The question is: how do we balance the health threat of chemical control with the health threat of mosquito-transmitted diseases?

Grasshoppers/Locusts

February 1931

Turkeys are a lot of darned hard work. They are as dumb as sheep and must be constantly watched lest they commit suicide in some stupid way. A lot of their feed is grasshoppers they catch in the fields and meadows.

August 1, 1936, Saturday

July has gone, and still no rain. This is the worst summer yet. The fields are nothing but grasshoppers and dried-up Russian thistle. The hills are burned to nothing but rocks and dry ground. The meadows have no grass except in former slough holes, and that has to be raked and stacked as soon as cut, or it blows away in these hot winds. Anne Marie Low – Dust Bowl Diary

Wild turkeys forage beneath Gambel oak in our yard. Presumably they are a bit smarter than their domesticated cousins.

Grasshoppers during the depression were both a blessing (turkey food) and a curse (eating the crops). As the drought grew worse through the 1930s, grasshoppers just added insult to injury. They didn’t really make things worse for Low’s family, because things were already as bad as they could get.

Lack of rain had decimated crop yields. On top of that, there was no market for what did survive. Even recouping costs was not likely. Planting in the first place was simply a futile exercise. Seed blew away in the wind. Very little germinated and anything that grew was stunted and eventually died of dehydration or burnt to death in the unrelenting sun.

In the 19^th century, crops on the Great Plains suffered from the voracious appetites of Rocky Mountain locusts. The outbreaks were not related to drought, but were equally devastating. Locusts differ from other grasshoppers in that they may be solitary at times, but also have a swarming phase.

In 1875, the largest swarm in history was recorded.  The swarm in flight covered an area approximately 1800 miles long and at least 110 miles wide. Three consecutive years of swarms decimated untold acreage of farm crops on the northern plains.

Despite the seemingly ubiquitous plague, these locusts went extinct by the 20^th century from unknown causes. The dark clouds of insect bodies that once filled the skies, much like the also-extirpated passenger pigeon, vanished from the earth.

Bark Beetles

In 2005, I worked as an intern at Mesa Verde National Park in the Natural Resources department. I kept a detailed journal regarding everything I learned or did while there.

May 26, 2005

Only 200 Ponderosa pine left in the park (relics of the Pleistocene). The piñon-juniper burned in the fire will not resprout – soil conditions will not allow germination – crown fire that consumes everything in its path. The beetle attacking piñon goes after younger trees, not the oldest. Maybe oldest trees have some defense? The drought and a bark beetle have killed off the uppermost limbs of the Gambel oak – makes landscape look gray, but the plants aren’t dead.

A dying piñon pine (lower center) and several dead ones, probably killed by beetles – near Moab, Utah. These pines typically decay and topple within two years, but I’ve seen them remain standing a decade or more.

Drought-stressed plants, even tolerant species such as piñon pine and juniper, have suffered over two decades of dry periods. But climate change is a factor in another way. As winters have warmed, bark beetle outbreaks have become more common. Sub-zero temperatures for several weeks are needed to keep populations in check. This doesn’t happen anymore.

After the drought of 2002, it was estimated that beetles killed as much as 80% of the piñon pine trees in southwest Colorado. Bird species that depend on the pine seeds suffered as a consequence. Only in the last few years does it seem to me that jays and nutcrackers are starting to rebound.

June 18, 2018

Over the central Colorado mountains as I fly from Durango to Denver, I look down and realize just how extensive the bark beetle kills (pine and spruce) have turned our signature landscape from green to brown.

Some people wish to log these landscapes, thinking they are more fire-prone than live forests. The science seems to dispute this notion. Dead trees lack needles, which burn more quickly than the wood of the trees. In a live forest, the flames rapidly dry out the needles and set them ablaze.

Overcrowded trees allow high-intensity crown fires to occur. These dense second- and third-growth forests are probably more apt to burn than those killed by beetles. The standing and fallen dead trees are beneficial to a variety of wildlife, including many bird species that feed and nest in the snags.

The question is: should we allow naturally occurring beetle-killed trees, in forests drastically altered by human interference, to recycle naturally?

(See the Introduction here)