Potential Industrial Application of Allelochemicals and Their Problems

Chapter 40

Potential Industrial Application of Allelochemicals and Their Problems

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on August 23, 2015 | http://pubs.acs.org Publication Date: January 8, 1987 | doi: 10.1021/bk-1987-0330.ch040

Han San Ku SDS Biotech Corporation, Painesville, OH 44077

Agrochemical research, by both industrial and academic scientists, has provided compounds of progressively increased activity, with recently discovered insecticides, fungicides, nematicides, herbicides, and plant growth regulators showing outstanding potency. Most of these chemicals are targeted at visible pests, such as weeds and insects. The chemical effect is observable and can be quantified. Such effective pesticides and other agrochemicals are not yet available for several other targets of interest, such as soil-borne pests and diseases (viruses, bacteria). However, i t is becoming more difficult to find new chemical entities by using the traditional approaches. Allelochemical research is an area of interest to agrochemical companies, because i t provides a new way to control pests, as well as sources of new chemicals to address other problem areas in agriculture. Use of chemicals in food, feed, and fiber production is an important element in modern agricultural practice. Chemical companies have been providing effective crop protection chemicals, as well as cheap fertilizers, through cooperative research and development programs for the last four decades. These companies are s t i l l continuing their attempt to develop new products that will act only on the target pests and have a minimum risk of side effects. However, the probability of finding a product having a l l the desired characteristics is decreasing. Today, only about one out of every 10,000 chemicals screened enters the second phase of testing, which means the stage of extensive field evaluation. Among about five extensively field tested chemicals, one may become a marketable product. Allelochemicals provide a possible new approach to control pests,, as well as sources of new chemicals that may lead us to discover more biologically active compounds and new ways to grow high-yielding and better quality crops. Some of these approaches are discussed by others in this book. 0097-6156/87/0330-0449$06.00/0 © 1987 American Chemical Society

In Allelochemicals: Role in Agriculture and Forestry; Waller, G.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

450

ALLELOCHEMICALS: ROLE IN AGRICULTURE AND


Discovery and Review of New A g r i c u l t u r a l

FORESTRY

Chemicals

In order to i l l u s t r a t e the potential of the application of an allelochemical i n agrobusiness, l e t us look at the h i s t o r i c a l p r o f i l e of agrobusiness. We have accumulated vast s c i e n t i f i c knowledge of how to make new molecules and how the chemicals work. We have better equipment, f a c i l i t i e s , and tools to help us study these molecules and yet we have to accept the fact that innovation i n this f i e l d i s becoming more and more d i f f i c u l t . We expect the rate of introduction of new a g r i c u l t u r a l chemicals to diminish markedly i n the future. Table I certainly demonstrates these points. Table I.

Rate of Discovery and Development of Major Pesticides from 1931 to Date Major P e s t i c i d e s Introduced

Decade

1931 1941 1951 1961 1971 1981

-

1

1940 1950 1960 1970 1980

9 18 19 8 3

The introduction of products for use i n minor crops has become almost impossible because of the low economic incentive. The frequency of introduction of major money-making compounds has been decreasing sharply, although chemical companies have been increasing their t o t a l R and D budget. Keep i n mind that most of this budget i s being spent on defense of existing products rather than i n discovery programs. For example, i n the I960 s and 1 9 7 0 ' s , chemical companies enjoyed vast growth by developing good economic returns (DDT, organophosphates, carbamates, pyrethroids, t r i a z i n e s , acetanilides, glyphosate, e t c . ) . In the 1 9 8 0 ' s , that kind of growth has not been seen yet. Another reason for decreasing introduction of new products i s i l l u s t r a t e d i n Figure 1. The work required to demonstrate the safety of candidate products and to s a t i s f y r e g i s t r a t i o n and other regulatory bodies has become one of the largest portions of budgets and a time-consuming process. Let me make i t quite clear that chemical companies don't question the need for careful regulations. I t i s a fact that we need a careful r e g i s t r a t i o n process to assure the product i s safe and has minimal impact on the environment and minimal effects on nontargeted organisms. Since the cost of developing a new a g r i c u l t u r a l product i s so high, we have to consider several factors before the compound i s evaluated. The factors are outlined i n Table I I . Please keep i n mind that these factors are also things we have to consider on allelochemicals for commercialization. These factors 1

are:

(1)

Biological

Efficacy.

kg active ingredient/ha rate was

In

the

1960»s

and

1 9 7 0 » s , one

to

two

an acceptable rate of application;


40.

KU

Potential


Table I I .

1. 2. 3. 4. 5.

Industrial

Application

Factors Affecting New Control Agents

ofAllelochemicab

451

A g r i c u l t u r a l Chemical/Biological

B i o l o g i c a l Efficacy (Rate, Resistance) Cost (Manufacture; Treatment) Health, Toxicology Environmental Impact Method of Application

now we consider 1 kg/ha rate too high. Most of today's new products are used at a rate below 0.5 kg/ha. Resistance problems are another concern, especially for insecticides and fungicides and, more recently, certain herbicides. I f cross resistance to a new compound i s found, then further development may be cancelled. (2) Cost. The manufacture and treatment per acre should be cheaper than for existing products or offer some other advantage over those on the market today. I f the compound i s for a minor use or for use only i n minor crops, the project could be suspended. For example, i f a compound i s only to be used i n onion or cabbage as a herbicide, the market i s not large enough to permit recovering the cost of the R and D; therefore, most companies w i l l put that compound back on the shelf and i t w i l l never reach the market. (3) Health and Toxicology. I t need not be emphasized how important t o x i c o l o g i c a l information i s to any a g r i c u l t u r a l product; just look at the money spent on toxicology. In general, i f acute oral LD values are below 50 mg/kg, a company w i l l mark the program with a ^yellow f l a g " , meaning extreme caution. (4) Environmental Impact. Again, I hardly have to mention the importance of environmental data; look at the requirements for environmental impact data for r e g i s t r a t i o n of a g r i c u l t u r a l products. (5) Method of Application. This i s an important research area which t i e s into development of formulations, especially for s o i l pesticides or r e l a t i v e l y v o l a t i l e products. Now l e t us examine some properties of recently introduced a g r i c u l t u r a l chemicals such as Glean, Arsenal, and T i l t . I t i s of interest that a l l of them have the following common c h a r a c t e r i s t i c s : (1) low application rate: e f f e c t i v e rates of these compounds are only several oz./acre or grams/ha; (2) a l l of them have very low mammalian t o x i c i t y ; i n other words, they are very safe compounds as to acute oral t o x i c i t y ; (3) a l l of them are targeted to special uses; (4) some of them were o r i g i n a l l y found i n b i o l o g i c a l materials and the major mode of action was thoroughly studied. Next we consider the process of developing a new a g r i c u l t u r a l product. Figure 2 i s just a simplified chart. I t may vary from company to company, from compound to compound. This whole process normally takes 7 to 10 years and more than $40 m i l l i o n .


452

ALLELOCHEMICALS: ROLE IN AGRICULTURE AND FORESTRY


Field trial

Toxicology, residue, metabolism Environmental fate

Screening, greenhouse, small field plot tests

—I—I—I—I—I—I—I—I—I

v Y

e

a

Figure 1.

r

1

2

Simplified

3

4

6

6

7

diagram f o r r e g i s t r a t i o n

Idea, O b s e r v a t i o n

8

9

of new p e s t i c i d e .

Synthesized New chemicals

Prepare small quantity of material

t» Screening, special tests

•

Potential Industrial Application of Allelochemicals and Their Problems

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