Nuisance Mosquito Spraying: Non-Target Victims

August 5

When the unmistakable buzz of spray truck became audible, I uttered an expletive for the first time in more than a decade. I had about a dozen first to third instar monarch caterpillars in the “outdoor nursery” under a mosquito netting.

I ran out to move the potted milkweeds and caterpillars into the garage. With a small container of water and a paper towel, I carefully wiped down leaves that I thought might be contaminated then hoped for the best.

According to information on our mosquito abatement organization’s website, the chemical is sumithrin. The amount in the spray, or fog, to be more accurate, is supposed to be very low: low environmental impact, quick degradation, safe for birds and mammals, and it must hit mosquitoes in flight to kill them. Nothing about effects on any non-mosquito arthropod. I emailed staff entomologist asking the chemical’s effects on butterfly caterpillars. Other websites mention that insects similar in size to mosquitoes might suffer and temporary drop in non-target insect population has been observed.

In between days

Spraying on August 5 somehow spared my outdoor nursery caterpillars. Next morning, I collected milkweed leaves, rinsed them like usual and fed them to my indoor monarch caterpillars without issue. A female monarch deposited some eggs. The ones I found and quickly rinsed with tap water hatched all hatched. Actually, that spraying wasn’t too effective. I got bit pretty good, especially from neck and up.

Mosquito abatement returned my email with two pdf attachments- Anvil 10+10 Label and Anvil 10+10 MSDS. It also wrote that I should contact the manufacturer about effects on butterfly caterpillars. I didn’t immediately review the literature assuming they wouldn’t spray again for a while.

August 11

My neighbor’s adult daughter having an outdoor late afternoon-evening-late night birthday party wouldn’t affect the nursery caterpillars. Not really knowing why, I took them into the garage for the night anyway. Around 9:30 pm, the buzzing came. I closed all the windows, just in case. The birthday party got fogged.

Around 10 pm, my feral cat Tootsie and I were out when the spray truck rolled into the cul-de-sac behind my backyard. I grabbed and held onto Tootsie underneath the awning to avoid the fog. She was not happy. The party got fogged again.

After the fog dissipated while playing with Tootsie, no mosquito bothered me. It occurred to me that although the feral cat water bowel was sheltered, it should be cleaned. As I reached for the bowel, I saw a crane fly(?) convulsing. A few inches away, an ant was doing the same. These were definitely larger than an average mosquito.

Surveying the backyard. Japanese beetles on top of butterfly bush, earwigs on top of milkweed leaves and pill bugs out in the open were unaffected. I dealt with the Japanese beetles. Sounds of crickets didn’t diminish. A small white moth fluttered around but it might be sheltered during the foggings. A lacewing wasn’t so lucky.

August 12

I found a dead skipper and a dead bee(?). They might be victims too. I’ve seen skippers and solitary bees out in the open on plants at night.

dead skipper

dead bee

Eastern Comma Butterfly Caterpillars

August 7

A butterfly that I couldn’t identify last year was acting like a female butterfly looking for a place to deposit eggs. She darted in and out of the bushes as Tootsie watched. I tried to keep an eye on both. Tootsie is often successful catching egg-laying female butterflies not paying attention to anything else. Based on the few fuzzy images I got and the internet, she seemed to be an eastern comma butterfly.

eastern comma butterfly, probably, depositing eggs

She deposited 3 eggs underneath a leaf of some kind of a plant. The arrangement of the eggs was odd to me.

3 eastern comma butterfly eggs- one by itself, one stacked up top of another

A cutting of that host plant doesn’t keep in water and wilts quickly.

August 10

Three caterpillars emerged. They didn’t eat the egg casings. They could be mistaken for monarch caterpillars at the same stage.

3 newly hatched eastern comma caterpillars

eastern comma caterpillar eleven hours after it hatched

August 12

The caterpillars should have fresh food. I brought them a fresh cutting of the host plant. Two caterpillars noticed immediately and started heading that way. Minutes later, I found one drowned in water. Another one went missing but not in water. The last one eventually moved to a new leaf.

eatern comma caterpillar eating leaf possibly contaminated with sumithrin

A few hours later, I noticed the last one moved to another leaf and was convulsing. The one that went missing but didn’t drown was already dead on the same leaf! In less than 6 hours, they all died.

dead, shrunken eastern comma caterpillar

Anvil 10+10 photodegrades. Maybe I didn’t wait long enough. Still, I was surprised that rinsing didn’t work.

Of course a female monarch came laying eggs in the afternoon. I took in the leaves with the eggs. Fearing the leaves might not have been under the sun long enough, I kept the leaves under full-spectrum CFL light for hours. All caterpillars successfully became chrysalises as of today, August 23.

In between days

The fogging was very effective. The neighborhood mosquitoes must have been fogged at the birthday party. I got bit once in 2 days.

Although the number of bites increased with each passing day, the number averaged about 4 to 5 per day instead of the 8 to 10 per day prior to August 11.

Also, after August 20 morning storm, mosquito number dropped again.

August 22

I lit one insect repellent stake then moved it around with me as I weeded. Not a single bite for two and half hours among the tall weeds. Forecast of waves of storms Tuesday and Wednesday. Wet and overcast are not optimal conditions for the pesticide to degrade. More mosquitoes will have hatched from eggs in a few days after. So I was very surprised when I heard that buzzing before it was completely dark.

There were two 1st instar monarch caterpillars in the outdoor nursery. I overlooked them as eggs. A female monarch deposited a bunch of eggs on August 20- 3 in the nursery and about 30 I took inside. I took the pots into the garage just before the flashing yellow light and the fog came around.

A major problem- I must feed 20 caterpillars, 2nd to 5th instar. I didn’t keep enough safe, quality food inside. Good quality milkweed leaves are already hard to find at this time of the year. I did accidentally cut off an iffy stalk of milkweed while weeding. I kept it not certain if it was fungi- and disease-free. When it seemed that the four 5th instar caterpillars would finish one of the 2 small, tender milkweed cuttings before morning, I gave them the iffy milkweed.

Lonely Firefly (aka lightning bug)

During the past few nights, there was one firefly signaling its existence. None of its kind replied. Firefly season was July. I prefer their gentle, quiet, random sparkling in the dark much more than violent, house-rattling, ostentatious fireworks. It showed up late but I welcomed it. It was wafting and flashing in the backyard when the truck came. Afterwards, no sign of it. Another non-target victim?

August 23

All four 5th instar caterpillars ate from the iffy milkweed and they are sill alive. About half an inch of rain came down in the morning. I had to take a few milkweed cuttings, hoping that the rain might wash off the pesticide residue, additional rinsing by me and some time under CFL light would make these safe to eat. We will see.

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