Battling Insects

Inali and I went for a walk this morning and came across an exterminator at a neighbor’s house. This always raises my hackles.

1. How can people think that spraying chemicals to kill one kind of animal doesn’t have an unintended affect, in some way, on other animals, including humans?
2. If they have to keep doing it on a regular basis, why don’t they question the usefulness of the practice?

Anyway, in this instance the bigger frustration was that emblazoned on the “we kill bugs” insignia was a green lacewing (Chrysoperla plorabunda). This insect is an important predator species. As a juvenile it eats aphids and other insects.
This is an example of an insect you should encourage to live in your yard. You will not do that by spraying insecticide which kills nondiscriminatively.

My neighbors right next door have an exterminator service that sprays all around their house every four months. (I know this because I stand at the side gate, making sure they do not spray into my yard.) The neighbors have been doing this for 15 years and they continue to have an ant and roach problem. And here’s the topper, their three grandchildren, all under the age of five, play in that sprayed grass.

Right next door, we do not have a problem.

Because of our tortoises we have never used sprays in our yard. For the first few years that we lived here we did put out ant bait in containers and snail pellets in the front yard. The pest species populations would ebb, but always return. Then we stopped completely to see what would happen.

We also started removing the water-hungry, exotic ornamental plants and replaced them with native plants. Our ant problem began to decline. The ants that cause problems all along coastal California are an invasive species, Argentine ants (Iridomyrmex humilis). Our native plants are less willing to give away sweet sap to insects. They have tough waxy coverings or hairs that thwart Argentine ants. This South American ant species also requires water. Routine shallow watering provides the perfect habitat for them to thrive. They don’t create deep nests, they stay close to the surface. A dripping faucet beside a stepping stone is their idea of paradise. Reduce that regular watering, fix leaky plumbing, and it becomes harder for them to make a living.

I do still have ornamental roses, but if my roses are insecticide free the green lacewings and the lady bugs, as well as the bushtits and wrens keep the insect population to a minimum.

When you build a house, you are building it on land where other creatures lived before you. Like any landowner, they will try to reestablish their right of ownership. Other insects will come if habitat is offered. If you create a water-dependent English garden in a southern California Mediterranean climate, you are creating an oasis for invasive exotic pest species.

Native plants are just as beautiful and native insects have predator species that keep them in check without my lifting a finger.

So stop spraying and the next time you see a green lacewing thank it for the job it does in your garden.

Backyard Biodiversity Project - Zone 17

Part of surveying the plants and animals of Hummingbird Hill is recording all the data. I’ve divided the property into Zones. The Zones are different sizes but each is a type of habitat.

Zone 17 Description

• Location: Planter in front of house on a North facing slope, from driveway to the eastern property edge. Includes driveway in front of house.
• Soil Condition: Poor, concrete and gravel over clay
• Water Availability: Manual hose irrigation and rain
• Climate: Dry, sun
  
• Human Traffic: Minimal, but daily car traffic across driveway
• Animal Traffic: Minimal canine passing through

I’m interested in Native vs. Exotic species - who is surviving, who is not. Who is feeding on whom. What animals are interacting with which plants. The hardest task is finding a good source for identifiing the small creatures and the “weeds.”

Zone 17 General Notes:

• Densest populations of animal species were found in specific areas. Dominant species are scale and aphids; exotic cottony cushion scale (Icerya purchasi) [on Native holly cherry] and exotic oleander aphid (Aphis nerii) [on exotic oleander] 170; and Native rose aphid (Microsiphum rosae) 50 [on exotic oleander]. Small milkweed bugs (Lygaeus kalmii) constituted a reproducing population of natives on the ground among the gravel. Spiders were found on the oleander stumps. All other animals were singletons or deceased populations.
• Dominant plant species is unidentified. Most successful plants are volunteers in cracks of driveway.
• Exotic snail and crustaceans only represented by deceased bodies possibly due to drought.
• The greatest species diversity was among spiders, 7 species and insects 10 species.
• 31 species identified - 25 animals, 6 plants
• Greatest population - cottony cushion scale (Icerya purchasi) 200 individuals and yet-identified volunteer ground cover, 34 plants.
• Currently no birds, reptiles or mammals live in this Zone, though birds have nested here in the past.
• Animals out number plants. Natives out number Exotics.
  

Native Insects:

1. rose aphid, Microsiphum rosae, 50 (feeding on oleander)
2. California carpenter bee, Xylocopa californica, 1
3. small milkweed bug, Lygaeus kalmii, 67
4. gray bird grasshopper, Schistocerca nitens, 1 (body parts left by predator)
5. black gnat, Bradysia impatiens, 1

Exotic Insects:

1. oleander aphid, Aphis nerii, 170 (feeding on oleander)
2. Argentine ant, Iridomyrmex humilis, 1 (one the garage door)
3. cottony cushion scale, Icerya purchasi, 200 (feeding on holly leaf cherry)
4. oleander scale, Aspidiotus nerii, 1 (feeding on oleander)

Not yet identified:

1. long-legged fly, Dolichopodidae ssp type, 1

Native Spiders and Crawlies:

1. round snail, Discus whitneyi, 3 dead
2. soil mite, Oribatei spp., 1
3. corner spider, Hololena curta, 3
4. trashweb spider, Cyclosa turbinata, 10

Exotic Spiders and Crawlies:

1. brown garden snail, Helix aspers, 6 dead
2. common pill bug, Armadillidium vulgare, 4 dead

Not yet identifed Spiders and Crawlies:

1. snail, cone type, longer than wide, 1 dead
2. spider unidentified, ‘1 mm’ brown, 1
3. spider unidentified, ‘3 mm’ brown no web, long front legs, 2
4. spider unidentified, ‘ant-sized’ black, 1
5. spider unidentified, ‘ant-sized’ black with web, 1

Native Birds:

1. band-tailed pigeon, Columba fasciata, feather
2. California towhee, Pipilo crissalis, 1

Native Mammals:

1. desert cottontail, Sylvilagus audubonii, scat

Exotic Mammals:

1. fox squirrel, Sciurus niger, 1

Native Plants:

1. sow thistle, Sunchus ssp., 15 (volunteer in driveway cracks)
2. spotted spurge, Euphorbia maculata, 1 (volunteer in driveway cracks)
3. annual bluegrass, Poa annua, 2 (volunteer in driveway cracks)
   

Not yet identified:

1. ground cover with white flowers, 34 (volunteer in driveway cracks)

Exotic shrub:

1. oleander, Nerium oleander, 4 (recently cut to the ground)

Native tree:

1. holly leaf cherry, Prunus ilicifolia ilicifolia, 2 (volunteers)