Sunday, June 15, 2014


Weather: Hurricane Christina threatened the south western coast of México; we got high winds, some rain and a little hail; last rain 6/13/14.

What’s blooming in the area: Catalpa, Dr Huey, pink species and hybrid roses, yellow potentilla, silver lace vine, weeping yucca, daylily, red hot poker, chives, peony, datura, oriental poppy, larkspur, Jupiter’s beard, golden spur columbine, pink evening primrose, blue flax, alfalfa, sweet pea, purple-flowered salvia, Shasta daisy, yellow yarrow, Brome grass.

Beyond the walls and fences: Tamarix, alfilerillo, tumble mustard, tufted white evening primrose, scarlet bee blossom, purple mat flower, fern leaf globemallow, oxalis, pink and white bindweed, yellow sweet clover, showy milkweed, amaranth, Hopi tea, goat’s beard, native and common dandelions, plains paper flowers.

In my yard, looking east: Maltese cross, Bath pinks, snow-in-summer, baby’s breath, pink-flowered salvia, winecup mallow, coral bell.

Looking south: Betty Prior and Fairy roses.

Looking west: Johnson’s Blue geranium, Rumanian sage, purple beardtongue, catmint.

Looking north: Coral beard tongue, chocolate flower, blanket flower, coreopsis.

In the open, along the drive: Dutch white clover, California poppy, white yarrow.

Bedding plants: Pansies, snapdragon, sweet alyssum, blue salvia, French marigold.

Seeds: Morning glories and red flax have first leaves.

Animal sightings: Rabbit, geckos, small birds, cabbage butterfly, ladybugs, grasshoppers, harvester and small black ants, a few bees and a hawk moth on the Seven Hills Giant catmint.

Weekly update: DDT began as a chemistry student’s experiment in the 1870s. Othmar Zeidler was systematically testing permutations of bromobenzene for his dissertation at the University of Strasburg.

Dalmatian pyrethrum was the common insecticide then for killing mosquitoes and lice. Tanacetum cinerariaefolium grew in Mediterranean grasslands along the eastern Adriatic coast, but Japan became the major supplier for the United States.

With World War II, both Croatia and Japan became allied with enemy forces. The Bureau of Entomology and Plant Quarantine was left with finding a substitute for pyrethrum.

Paul Hermann Müller had begun researching moth repellants for the J. R. Geigy Dye Factory in Basel in 1930s. He tested one promising compound, diphenyltrichlorethane, then searched the scientific literature for compounds with similar chemical structures. He found Zeidler’s work. Dichlorodiphenyltrichloroethane not only was effective, but did not disappear. Pyrethrum was useful, but was destroyed by exposure to UV rays from the sun.

DDT dominated the pesticide market until Rachel Carson published Silent Spring in 1962. She documented the ecological destruction caused by the persistence that had attracted Müller.

Chemical companies tasked their researchers with developing substitutes. They began with the work of Herman Staudinger and Lavoslav Ružièka. The German and Croatian scientists had identified the chemical structure of pyrethrin, the active agent in pyrethrum in 1924.

In the early 1960s, Michael Elliott of the Rothamsted Experimental Station in Harpenden, Hertfordshire, altered the molecular structure of pyrethrin. His second generation pyrethroid, resmethrin, was effective against house flies, but unstable in sun light.

In the early 1970s, Elliott solved the UV problem. Permethrin, the third generation pyrethroid, was released in 1972, the same year the United States banned most uses of DDT.

Bifenthrin, the active agent in the insecticide I used a week ago, is considered a fourth generation pyrethroid, with greater resistance to UV rays. It has the advantage that it is not water soluble, so doesn’t migrate through the soil. It has the disadvantage that it kills all insects, including ladybugs, and can’t be used need streams. It’s negative effects on humans seem limited to high dosage exposures.

A Geneva convention in 2004 outlawed the use of DDT for everything except controlling malaria carrying mosquitoes. FMC Corporation of Philadelphia, the company that introduced bifenthrin, is now promoting its use on saturated netting used in Africa to control malaria.

Organic farmers still rely on pyrethrum. Botanists have bred strains that contain greater concentrations of pyrethrin than wild populations. The primary producers are subsistence farmers in Kenya and commercial growers in Australia.

Grdiša, Martina, Klaudija Caroviæ-Stanko, Ivan Kolak, and Zlatko Šatoviæ. "Morphological and Biochemical Diversity of Dalmatian Pyrethrum (Tanacetum cinerariifolium (Trevir.) Sch. Bip.)," Agriculturae Conspectus Scientificus 74:73-80:2009.

Kinkela, David. DDT and the American Century (2011)

Zitko, Vladimir. "Chlorinated Pesticides: Aldrin, DDT, Endrin, Dieldrin, Mirex" in Heidelore Fiedler, Persistent Organic Pollutants, Volume 3 (2003)

Photographs: Catalpas have had a difficult spring. In the village, leaves opened when afternoons warmed in May, then were killed by the cold temperatures on May 14. The upper leaves were killed, but the ones nearer the ground or nearer the main trunk survived.

They’ve been blooming for more than a week, but the warm afternoons and high winds have apparently dulled the usually white flowers. This week the leaves on my tree were torn, either by the high winds or hail.

1. Catalpa in village, 29 May 2014, with leaves only on low limbs.

2. Same tree fully leafed, 15 June 2014, with flowers only on low limbs.

3. Next tree in row in village, 15, June 2014, with flowers only on limbs.

4. Catalpa along highway, with one barren branch, 29 May 2014.

5. Same tree fully leaved, 15 June 2014; flowers darkened prematurely, none on branch that leafed late.

6. Damaged catalpa leaves in my yard, 15 June 2014.

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