Insects and Weeds Hesearcfi for Toftiôrrow

[Heliopsis longipes (A. Gray) Blake], Natural mamey (Mammea americana L.), and neem (Azadirachta indica A. Juss.). Pesticides Although aU six could be commer- cially viable, the neem tree is by far Martin Jacobson, researc/i chemist, the most useful and likely to succeed. Insect Chemical Ecology Much applied research on agronomy, Laboratory, Agricultural commercial processing, and market- Environmental Quality Institute, ing is needed before commercial pro- Beltsville Agricultural Research duction of these species as sources of Center, Agricultural Research insecticides would be possible in the Service United States.

From the time of the early Romans CâfâftICIS. This plant (also known until 1900, only three plant-de- as sweetflag) is a member of the fam- rived insecticides—pyre thrum, helle- ñy Araceae. It is a semiaquatic robust bore, and nicotine—have had wide- perennial that can also grow on dry spread use. The discovery of rotenone land. Calamus is 5 to 6 feet tau, has a and several plant-derived insecticides horizontal rootstock, and grows at al- followed in rapid succession. Ad- titudes from 3,000 to 6,000 feet. The vances in chemistry and improved plant grows wild in the United States screening techniques have led to the from Florida to Texas and in Idaho, discovery of many plant-derived in- and in the various provinces of On- sect toxicants, repellants, attractants, tario and Nova Scotia in Canada. It is feeding deterrents, growth inhibitors, propagated by division in the spring and sterilants. or autumn. Some of these compounds, pro- The large rhizomes are repellent or duced by the plants as defenses toxic to clothes moths, house flies, against pests and pathogens, may be fleas, lice, mosquitoes, and many developed commercially from arid or stored-grain insects. Beta-asarone, the semiarid plants established as new component primarily responsible for crops. They would expand the range these pesticidal effects, is highly ef- of available products for insect pest fective against the rice weevil, which control as safe substitutes for some is probably the most damaging insect synthetic insecticides that are eco- pest of stored grains in grain eleva- logically disruptive and for others tors. Beta-asarone would probably be to which insects have developed very useful as a fumigant for protect- resistance. ing grain-filled storage areas without leaving residues on the grain after the Six Promising Plants areas are ventilated. Other potential uses of calamus compounds are for Six plants appear to be particularly the treatment of tuberculosis, as a promising. Not only are they good germicide, and in perfumery. sources of insecticides and related chemicals, but they are adapted to Basilm Sweet basil is a smooth or areas that are marginal for production slightly pubescent aromatic herb with of traditional food and fiber crops and white or slightly purplish flowers. It represent potential multiproduct crops was experimentally cultivated from for the United States. They are cala- seed by USDA in Virginia for several mus (Acorus calamus L.), hasü (Oci- years in the 1930's. The seed was im- mum hasilicum L.), big sagebrush ported from France, and the whole (Artemisia tridentata Nutt.), chilcuan fresh flowering herb was used for dis-

144 INSECTS AND WEEDS Research for Tomorroiv tilling the oil. The plants grow rapidly on clay sou improved by mulching with manure and reach a height of 13 1^2 to 16 feet. Good yields of the oil may be produced in many parts of the S United States and sold at reasonable prices. In addition to its widespread use as a spice, sweet basu, which is a mem- ber of the family Lamiaceae, is rec- ommended for use against gastric dis- orders, malarial fevers, and skin diseases, and for insect control. The oil distilled from the fresh flowers or the entire plant is used extensively as a flavor in confectionery, baked goods, condiments, and spiced meats, and as an aroma in certain perfume ^ •'^BB compounds. It is also an effective re- pellant and larvicide for mites, aphids, ^^^^^F' ^^^^^H and mosquitoes; a growth inhibitor m for milkweed bugs; and a fungicide. Although not aU the repellent com- ^HR^^ ' i^.^Bi^H pounds have been identified, cineole, linalool, and methyl chavicol are im- plicated. Two compounds, designated 1 as "juvocimene I" and "juvocimene II," are responsible for the growth in- Neem-based insecticide is sprayed on a chrysanthemum to test its efficiency hibition of milkweed bugs. against leafminers. Big Sagebrush. A member of the family Asteraceae, big sagebrush is a rapidly growing multibranched aro- tato beetle from feeding. (The beede's matic perennial that is the dominant resistance to insecticides in potato- plant of the Great American Desert. It growing areas is an increasingly seri- has been in the West since 1881 as a ous problem, and this resistance fodder plant for range cattle and oc- probably will become widespread.) curs wild in parts of Utah, Colorado, Various parts of the plant are used to northern Nevada, and northern Ari- destroy or expel parasitic worms. One zona, where it reaches a height of 10 compound responsible for preventing feet. The plant thrives in light, well- feeding has been identified as deace- drained, dry, stony soUs. toxymatricarin. Like many other spe- The leaves and shoots are placed in cies of Artemisia, big sagebrush con- granaries to protect stored cereals tains absinthin, which is avoided by from weevils and other pests, and the insects. water in which they are steeped is used to kill or repel insect larvae, Chïfcuan. Chilcuan is a perennial fleas, and locusts. Several species of herb, 4 to 11 feet tall, in the family ticks are kiUed rapidly by exposure to Asteraceae, native to Mexico but emi- the vapors of the plant. An extract of nently suited for cultivation in the the branch ends is exceptionally ef- mountainous regions of the United fective in preventing the Colorado po- States. Its roots are used locally in

Natural Pesticides f45 Research for Tomorrow

Tropical neem trees thrive tiiroughout the Caribbean and could do well in Southern Florida and Hawaii, according to ARS scientists.

146 INSECTS AND WEEDS Research for Tomorrow

Mexico as a spice, medicine, anes- when fuUy grown. It is common in thetic, and an insecticide; root ex- dry scrub forests of India (at least 14 tracts are effective against house flies, million are known to occur there) and mosquitoes, body lice, cockroaches, other countries of Asia and Africa, clothes moths, bean weevils, and and is being cultivated in several other household and agricultural countries of the West Indies and Cen- pests. The compound responsible for tral and South America. Experimental the insecticidal properties has been plantings of neem are thriving in identified as an amide that has been southern Florida, Puerto Rico, and given the names "affinin" and the U.S. Virgin Islands. Young trees "spilanthol." grown from seed seem able to survive Wild plants have been transplanted the climate of southern California and successfully, in rows and beds at ele- Arizona. vations of 5,900 to 7,900 feet. The Although aU parts of the tree are plant also can be propagated commer- repeUent to insects, extracts of the cially by seeds. Roots of suitable size seeds axe outstanding as repeUants and quantity for harvest should be and feeding deterrents for a broad ready within 2 or 3 years after spectrum of economic agricultural planting. and household insects. Seed extracts deter at least 45 species of crop pests MBinsym This tree (family Clusi- in the United States from feeding, in- aceae), 39 to 59 feet tall bearing edi- hibit growth and development of oth- ble fruits, is found in Latin America ers, and render still others sterile. and the West Indies and is suitable Several species of nematodes and for growth as a commercial crop in fungi are also affected. Examples of southern Florida, Puerto Rico, and the most destructive insects affected the U.S. Virgin Islands. Mamey can are Japanese beetles, cucumber bee- be grown in Florida as far north as tles, Mexican bean beetles, aphids, Palm Beach. The flowers, fruits, tobacco budworms, rice weevils, con- seeds, and leaves are effective against fused flour beetles, and leafminers. a wide variety of insect pests includ- The 0Ü, obtained by pressing or ex- ing melon worms, fleas, ticks, lice, tracting the seeds, can be used for armyworms, mosquitoes, and cock- the manufacture of wax and lubri- roaches. The leaves have been used cants, and the seedcake left after ofl in the West Indies for many years as extraction makes an exceflent fertü- a wrapping around the stem of newly izer and cattlefeed. set garden plants to prevent garden Unlike most of the present insecti- insects from attacking them. The dur- cides available on the market, the able wood from the tree is used for seed extracts appear to be nontoxic to bunding furniture and houses; the humans and animals and are essen- sweet flesh of the fruit (known as tially not poisonous to plants. Because "mamey apple") is eaten raw or these extracts are absorbed by the tis- cooked; and the fruit juice makes a sues of the treated plant and trans- refreshing drink. located through the roots into the fob- A mixture of coumarins in the age (systemic activity), they offer plant is responsible for the pesticidal relatively long-lasting protection to effect, with the major component crops even after rain showers of high named "mammein" or "mameyin." intensity. Although several chemical com- NeBntm This hardy tree, also caUed pounds present in the seeds are re- "nim" or "margosa," (family Meli- sponsible for the pesticidal effects of aceae) may reach a height of 60 feet neem, the major active component is

Natural Pesticides 147 Research for Tomorrow a limonoid named "azadirachtin"; it can be used effectively as an insect- Biological feeding deterrent at concentrations as low as 1/10th of a part in 1 million Control parts of water. Lloyd A. Andres, research Neem is envisioned to grow effec- entomologist, Plant Protection tively in hot, dry climates with little Research Unit, Western Regional rainfall where other agricultural crops Research Center, Agricultural are unproductive (shallow, stony, or Research Service, Albany, CA sandy soils) or present a severe ero- sion hazard. The tree has a wide range of possibilities for economic development. Furthmr Rmmding Looking over the large grassy Chemical Defenses of Higher Plants, rmeadow in northern California's G.A. Rosenthal, Scientific American, Humboldt County, it is hard to imag- 254(1): 94-99, January 1986. ine that in 1945, the colorful but poi- Insecticides, bisect Repellents, and sonous weed St. Johnswort literally Attractants from Arid/Semiarid Land held this prime grazing land in its Plants, M. Jacobson, Workshop Pro- grasp. Property values had dropped to ceedings on Plants: The Potentials for the point that ranchers could not af- Extracting Protein, Medicines, and ford the recommended, albeit margin- Other Useful Chemicals, U.S. Con- ally useful, control treatments. gress, OTA-BP--F23, pp. 9, 28-31, That year, in an effort to break the 138-146, 219, September 1983. weed's hold on the land. University of Use of Plants and Minerals as Tra- Caüfomia and U.S. Department of ditional Protectants of Stored Prod- Agriculture entomologists introduced ucts, P Golob and D.J. Webly, Tropi- a shiny blue-green beetle, Chrysolina cal Products Institute Report G138, quadrigemina, into the area. The sci- 32 pp., August 1980. entists knew from studies in Europe, the native home of St. Johnswort, and in Australia, where the weed also had become a problem, that the beetle fed exclusively on St. Johnswort, or closely related plants, and would not become a pest on agricultural crops. Once released, the beetle adapted quickly to California conditions and by 1950, St. Johnswort was well on the way to being controlled. Tried and True Method Deliberate introduction of natural enemies to control pests goes back to the first U.S. project in 1888. Since then, it has been proved time and time again that introduced parasites and predators can control their pest hosts and, in fact, have saved farmers f48 INSECTS AND WEEDS