Chemical and Biological Agents in Forest Pest Management - ACS

1 Chemical and Biological Agents in Forest Pest Management Historical Overview VIRGIL H. FREED

Downloaded by 80.82.77.83 on May 18, 2018 | https://pubs.acs.org Publication Date: January 16, 1984 | doi: 10.1021/bk-1984-0238.ch001

Department of Chemistry, Oregon State University, Corvallis, OR 97331

To early settlers, the North American forests appeared limitless. They were often considered a barrier to travel, commerce and agriculture. As a result, the forests were cut and burned with little thought to conservation and reforestation. Within the past half century, and more so in the last two decades, we have realized that our forests are limited resources. Their value not only for timber, but for recreation and soil and water management has been recognized. With this came the realization of the need to manage the resource for the benefit of man and the environment. Various pests - insects, diseases, undesirable plant species - have long been recognized as threats to the standing timber and a barrier to reforestation. Many management techniques have been tried to abate these pests, but among the most effective have been found to be the chemical and biological agents. Interest in use of chemicals in forestry started many years ago by perceptive foresters. But early chemicals were limited i n number and effectiveness. Now an array of chemicals is available for pest management. The use of chemical and biological agents i n forestry, while important, is not so extensive as in agriculture. Treatment is usually required only once or twice i n growth cycle and that on scattered parcels of land. The utilization of forests by the public for recreation and as watersheds has lead to questioning the use of chemicals. Some groups vigorously protest the practice despite assurances of need and relative safety. On the resolution of this and certain other forest management issues hangs the future of our forests. 0097-6156/84/0238-0001 $06.00/0 © 1984 American Chemical Society Garner and Harvey; Chemical and Biological Controls in Forestry ACS Symposium Series; American Chemical Society: Washington, DC, 1984.


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To the e a r l y immigrants t o the North American c o n t i n e n t , the hundreds of m i l l i o n s of acres of f o r e s t must have appeared almost endless. I n t h e i r eyes, i t could have appeared as a l i m i t l e s s resource extending i n t o p e r p e t u i t y . For t h e i r numbers t h i s may indeed have been the case, but l i t t l e could they have reckoned with the p o p u l a t i o n growth, and w i t h i t the demand f o r f o r e s t products some 300 years l a t e r . While the f o r e s t was a supply of timber f o r homes, f u e l , and o f t e n times, food, they were a l s o sometimes regarded as a b a r r i e r . The l a b o r to c u t and burn the f o r e s t , to eke out crop land and impediments to v e h i c u l a r t r a v e l , were not regarded as a b e n e f i t . Thus, f o r years the migrants cut and burned t h e i r way u n t i l they crossed the Appalachians and began the process again a t the Rockies a f t e r having crossed the Great P l a i n s . In l a t e r years as demand f o r timber products boomed w i t h the p o p u l a t i o n , the economic value of the v i r g i n stands of deciduous and c o n i f e r o u s f o r e s t s became the foundation of s u b s t a n t i a l f o r t u n e s . Commercial lumbering moved westward w i t h the p o p u l a t i o n u n t i l reaching the P a c i f i c Coast w i t h i t s tremendous stands of Douglas F i r , Redwood, and P i n e . In some r e g i o n s of the country, notably the Northwest and now i n the Southeast, lumbering i s a major f a c t o r i n the economy. The Northwest i s a c l a s s i c i l l u s t r a t i o n of the economic importance of lumbering. The d e c l i n e i n demand f o r timber products, due t o the economy, r e s u l t e d i n a l o s s of thousands of jobs i n the P a c i f i c Northwest. The f i f t e e n to twenty b i l l i o n d o l l a r a year i n d u s t r y has been almost a t a s t a n d s t i l l . U n t i l i n t o t h i s century, l i t t l e thought was given to the need for c o n s e r v a t i o n of the timber resource, or r e f o r e s t a t i o n . The l a r g e t r a c t s of v i r g i n timber i n v i t e d e x p l o i t a t i o n , and when depleted, the lumbering moved on. A few w i t h s u f f i c i e n t f o r e s i g h t began to a p p r e c i a t e the need f o r conservation and management of t h i s resource. The p r a c t i c e began e a r l y i n F e d e r a l f o r e s t s and soon was p i c k e d up by the more p r o g r e s s i v e , l a r g e lumbering interests. F o l l o w i n g World War I I , greater a t t e n t i o n was given to management of the lumber resources. Large f i r m s began h o l d i n g t r a c t s of land f o r r e f o r e s t a t i o n and t a l k e d of s u s t a i n e d y i e l d . In p a s s i n g , I'd l i k e to mention a former s t a f f member of Oregon State U n i v e r s i t y who was one of the pioneers i n c o n s e r v a t i o n and r e f o r e s t a t i o n . He c o n t r i b u t e d much to the science of f o r e s t r y and demonstrated that w i t h the Douglas F i r a 50 year growth c y c l e was q u i t e adequate. Management of our f o r e s t s i s now w e l l a p p r e c i a t e d by almost everyone. The need to m a i n t a i n growing stands of timber f o r water management, e r o s i o n c o n t r o l , timber y i e l d , r e c r e a t i o n , as w e l l as f o r timber products and g r a z i n g , i s w e l l recognized.

Garner and Harvey; Chemical and Biological Controls in Forestry ACS Symposium Series; American Chemical Society: Washington, DC, 1984.

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FREED

Historical Overview

Some s t i l l debate the m u l t i u s e concept of f o r e s t s , but most acknowledge i t as a v i a b l e management p r a c t i c e .


Pests of the F o r e s t To the c a s u a l observer, i t would mostly appear t h a t our f o r e s t s grow w i t h l i t t l e a t t e n t i o n and have few problems. This i s not e x a c t l y the case. Very few p l a n t s are without t h e i r b i o l o g i c a l competitors, and our f o r e s t s are no exception (10). A long l i s t of i n s e c t pests t h a t a t t a c k both coniferous and deciduous t r e e s , are known. Some are introduced from other areas of the world, and some are indigenous to the North American c o n t i n e n t . Among the more f a m i l i a r of the i n s e c t pests i n c l u d e the tussock moth, spruce budworm, the l o o p e r , bark b e e t l e , the pine sawfly, woolly balsam aphid, shoot moth, gypsy moth, and many o t h e r s . Some a t t a c k the young t r e e s r e s u l t i n g i n death or at the very l e a s t , much reduced growth; i n the o l d e r stands, the i n s e c t s causing d e f o l i a t i o n or a t t a c k i n g the cambium, may k i l l or s e r i o u s l y weaken the stand w i t h s i g n i f i c a n t l o s s e s of timber y i e l d (10,11). Many of the i n s e c t s have a c y c l i c a l p o p u l a t i o n p a t t e r n . That i s , i n a given year under c e r t a i n circumstances, the popu l a t i o n w i l l explode causing extensive damage f o l l o w e d by a c o l l a p s e of the p o p u l a t i o n . Those opposed to the use of c o n t r o l agents i n the f o r e s t argue t h a t the best management i s simply to wait f o r the p o p u l a t i o n c o l l a p s e . However, i n the meantime, thousands of acres may be damaged or k i l l e d , and the dead or dying t r e e s become a d i s t i n c t f o r e s t f i r e hazard. Insects are not the only problem pests i n f o r e s t management. Other p l a n t s , i . e . , grass, shrubs, t r e e s , a f f o r d a s e r i o u s problem i n r e f o r e s t a t i o n and i n young stands (11). Indeed, as young stands develop, even t h e i r own k i n d may serve as a competi t o r and r e q u i r e t h i n n i n g to develop a commercial f o r e s t . A f t e r a f i r e or l o g g i n g , a v a r i e t y of p l a n t s w i l l s p r i n g up i n the open area. Grasses and c e r t a i n herbaceous p l a n t s may f i r s t occupy a l a r g e p o r t i o n of the bare area. These compete w i t h any young s e e d l i n g s f o r moisture, n u t r i e n t s , and o f t e n w i l l choke out the s e e d l i n g i n the f i r s t year or two. A l s o invading the area w i l l be the shrubs and c e r t a i n competitive t r e e s . In the P a c i f i c Northwest, p l a n t s such as salmonberry, ceanothus, manzanita, b l a c k b e r r y , and o c c a s i o n a l l y , leguminous shrubs w i l l completely i n h a b i t the l a n d . This makes r e f o r e s t a t i o n extremely d i f f i c u l t , i f not i m p o s s i b l e , without e f f e c t i v e c o n t r o l measures. L a t e r , stands of a l d e r or other t r e e s p e c i e s , competitive w i t h the c o n i f e r , w i l l overgrow the area causing damage and delayed growth to the c o n i f e r . I n s e c t s and competitive p l a n t s are not the only problems f a c i n g the t r e e , p a r t i c u l a r l y the young one. Vertebrates, ranging from s m a l l rodents through the deer and other unglates, do t h e i r share of damage. While the damage to l a r g e r trees i s i n s i g n i f i c a n t , the browsing on young seedlings i s much more s e r i o u s . Domestic l i v e s t o c k a l s o may be troublesome.


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BIOLOGICAL CONTROLS IN FORESTRY


Adding to the f o r e s t pest complex are a v a r i e t y of diseases. This can i n c l u d e p a r a s i t i c p l a n t s such as m i s t l e t o e , fungal d i s e a s e s , and a v a r i e t y of b a c t e r i a l diseases (10). Taken i n t o t a l , the pest complex has been estimated to cause annual l o s s e s equivalent to 12 to 18 percent of the t o t a l annual cut. This runs i n t o 15 or so b i l l i o n board f e e t per year. The l o s s e s are s i g n i f i c a n t enough to have i n t e r e s t e d f o r e s t managers i n the use of pest management methods to abate the problems. To be sure, the problems are g e n e r a l l y l o c a l i z e d and the management p r a c t i c e s f o r pest c o n t r o l are a p p l i e d on a q u i t e l i m i t e d area. Pest management p r a c t i c e s i n f o r e s t r y i n v o l v e only a s m a l l percentage of the standing timber, i n c o n t r a s t to a g r i c u l t u r e where a much l a r g e r percentage of the cropland i s t r e a t e d annually (10). Chemical and B i o l o g i c a l Agents of the Past The idea of use of chemical and b i o l o g i c a l agents i n f o r e s t management, i s not new. As long ago as 1918, a water s o l u b l e mixture was used to r i n g g i r d l e s of t r e e s of many species i n I n d i a . The m a t e r i a l , a p r o p r i e t a r y wood p r e s e r v a t i v e that has claimed to w i t h i n a few weeks k i l l the r o o t s as w e l l as the a e r i a l p o r t i o n s of the t r e e s . The a r b o r i c i d a l p r o p e r t i e s of a r s e n i c a l e were described i n 1920. These a r s e n i c a l s , u s u a l l y based on t r i v a l e n t a r s e n i c , were used f o r g i r d l i n g trees to k i l l them, and treatment of stumps to prevent regrowth. Other chemicals t r i e d i n the two decades between 1920 and 1940 i n c l u d e sodium or calcium c h l o r a t e , mineral o i l s , rock s a l t , copper s u l f a t e , creosote, and ammonium thiocyanate. These l a t t e r compounds w h i l e t r i e d never showed enough promise to be widely used (1,2). In the e a r l y 1940's, a new i n o r g a n i c chemical, not having the t o x i c i t y of some of the others, was introduced. The compound, ammonium sulfamate, proved q u i t e e f f e c t i v e as an a r b o r i c i d e , a p p l i e d e i t h e r i n f r i l l s or sprayed on the e n t i r e p l a n t (3,4). During t h i s era a l s o , various borates were used to maintain f i r e b r e a k s i n f o r e s t s through c o n t r o l of both herbaceous and shrubby p l a n t s (5). The i n t r o d u c t i o n of the phenoxy compounds - 2,4-D and 2,4,5T - i n the mid 40's, provided much more e f f e c t i v e a r b o r i c i d e s than had h e r e t o f o r e been a v a i l a b l e (2,6,8). C o n t r o l of many brushy species f o r s i t e p r e p a r a t i o n i n r e f o r e s t a t i o n was now a v a i l a b l e . Perhaps one of the e a r l y a p p l i c a t i o n s of t h i s was made by Fred F u r s t i n the Siuslaw N a t i o n a l Forest where approximately 10,000 acres of c o n i f e r , o v e r s t o r i e d by a l d e r , were released by treatment w i t h 2,4-D. Other chemicals used i n t h i s era included t r i c h l o r o a c e t i c a c i d (TCA), used i n g i r d l i n g t r e a t ment of t r e e s , and f o r c o n t r o l of grass p r i o r to r e f o r e s t a t i o n . A m i n o t r i a z o l e , a l s o introduced during t h i s p e r i o d , found some use f o r c o n t r o l of Rhus species and grass i n f o r e s t n u r s e r i e s .



1.

FREED

Historical Overview

However, the phenoxy a c e t i c a c i d s , 2,4-D and 2,4,5-T, were by f a r the most widely used, being employed f o r stand t h i n n i n g , c o n t r o l of brushy species i n r e f o r e s t a t i o n , and c o n t r o l of brush and trees i n r i g h t s of way (11). The i n s e c t i c i d e s used i n the e a r l y part of t h i s century d i d not lend themselves w e l l f o r c o n t r o l of i n s e c t s i n the f o r e s t . The heavy r a t e s of a p p l i c a t i o n of such m a t e r i a l s as lead or calcium arsenate, was i l l s u i t e d to the type of a p p l i c a t i o n equipment then a v a i l a b l e . I t must be remembered that a e r i a l a p p l i c a t i o n of chemicals i n f o r e s t r y came w i t h the improved planes a f t e r World War I I . Rotenone and pyrethrum, two i n s e c t i cides used i n a g r i c u l t u r e i n that era, had but l i m i t e d a p p l i c a b i l i t y i n f o r e s t r y because of t h e i r p r o p e r t i e s (10). DDT, discovered by Dr. M u e l l e r i n Switzerland, and used f o r i n s e c t v e c t o r c o n t r o l during World War I I , q u i c k l y found a p l a c e i n f o r e s t r y , as w e l l as a g r i c u l t u r e . The m a t e r i a l proved h i g h l y e f f e c t i v e i n the c o n t r o l of such i n s e c t s as the spruce budworm, tussock moth, hemlock looper, and many others. I t was widely used i n the Northeast f o r c o n t r o l of the introduced Gypsy moth during these e a r l y years. The low t o x i c i t y of DDT to mammals made i t to appear to be an e x c e l l e n t i n s e c t i c i d e f o r f o r e s t r y use. I t was only a f t e r subsequent s t u d i e s revealed the impact on other species that r e s e r v a t i o n s about i t s use was r a i s e d . Though p a r a s i t i c p l a n t s such as m i s t l e t o e , fungal disease, and b a c t e r i a l diseases were indigenous to the f o r e s t , then as they are now, c o n t r o l i n the standing timber was l a r g e l y achieved by management p r a c t i c e s . However, a f t e r c u t t i n g , chemical treatment, such as w i t h pentachlorophenol, would be employed. Chemical and B i o l o g i c a l Agents - Present Through the years since 1945, more and more b i o l o g i c a l l y a c t i v e chemicals have been developed, f i r s t f o r a g r i c u l t u r e and subsequently many adopted i n f o r e s t r y . By now, some 25 to 30 d i f f e r e n t chemicals are used as h e r b i c i d e s i n f o r e s t r y (11). They are employed f o r weed and grass c o n t r o l i n the f o r e s t n u r s e r i e s , preparing s i t e s f o r r e f o r e s t a t i o n , c o n t r o l of invading species i n young stands, and f o r t h i n n i n g and c o n t r o l of weeds and trees (9) i n the more mature stands. E q u a l l y , a number of new agents have been introduced f o r i n s e c t c o n t r o l . Following the c h l o r i n a t e d hydrocarbons came v a r i o u s organophosphate e s t e r s , among them such things as malathion, f e n t h i o n , and f e n i t r o t h i o n , carbamate i n s e c t i c i d e s such as the nmethyl naphthyol carbamate, and s y n t h e t i c p y r e t h r o i d s . The h e r b i c i d e s commonly used as a r b o r i c i d e s i n c l u d e members of the t r i a z i n e s , ureas, and u r a c i l s , f o r grass and weed c o n t r o l i n nursery and Christmas t r e e p l a n t i n g s . Other compounds i n c l u d e phosphonate and phosphate d e r i v a t i v e s , pyridine-based organic acids of high a c t i v i t y , and organic a r s e n i c a l s . Such a wide


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array of a c t i v e compounds allows s e l e c t i o n of an agent to c o n t r o l most of the troublesome p l a n t and woody species. The choice of an i n s e c t i c i d e i s somewhat narrower because of the c r i t e r i a that must be met i n f o r e s t use. Nonetheless, a number of the organophosphate and carbamate i n s e c t i c i d e s have been found to meet the necessary standards. For example, the i n s e c t i c i d e c a r b a r y l has been employed f o r c o n t r o l of gypsy moth and some of the r e l a t e d lepidopterous i n s e c t s of the f o r e s t . B i o l o g i c a l agents such as B a c i l l u s t h u r i n g e n s i s , BT, has been coming t o the f o r e as a f o r e s t i n s e c t i c i d e , as more has been learned about i t s use. A t t e n t i o n i s now being given a l s o to the v i r u s e s such as the p o l y h e d r o s i s v i r u s of the tussock moth. The s y n t h e t i c p y r o t h r o i d s , as would "be expected, engaged the i n t e r e s t of those concerned w i t h c o n t r o l of f o r e s t i n s e c t s . These h i g h l y a c t i v e compounds, whose chemistry i s based on a n a t u r a l product, may o f f e r considerable p o t e n t i a l . I n t h e i r e a r l y use, or even y e t i n the developmental stage, are such things as the pheremones, j u v e n i l e hormone, and exoskeleton i n h i b i t o r s , as p o t e n t i a l agents i n f o r e s t pest management (12). Chemical and B i o l o g i c a l Agents - Future I t would appear that we are coming on a time where much more e f f e c t i v e and s a f e r chemical and b i o l o g i c a l agents f o r f o r e s t pest management w i l l be developed. But even beyond these new agents that w i l l be coming on i s a keener i n s i g h t and more c l e v e r ways i n which t o use these agents t o the b e n e f i t of f o r e s t management. As to agents f o r c o n t r o l of p l a n t s and u n d e s i r a b l e trees* i t would appear that i n the foreseeable f u t u r e we w i l l r e l y on s y n t h e t i c chemicals. There are, under development and i n use, some chemicals that are a p p l i e d a t ounces rather than pounds per acre f o r c o n t r o l of p a r t i c u l a r l y , grasses. I t h i n k we can expect to see as a f o l l o w i n g development, equally a c t i v e compounds developed f o r c o n t r o l of the broad l e a f and woody species. I n the more d i s t a n t f u t u r e , we may be able t o f i n d ways of using a l l e l o p a t h y f o r managment of undesirable species, but much i s to be learned about t h i s y e t . I n terms of b i o l o g i c a l agents, we can only hope that some of the experiments now going on i n v e s t i g a t i n g s p e c i f i c f u n g i f o r c o n t r o l of c e r t a i n species. I t i s the f i e l d of f o r e s t i n s e c t c o n t r o l that the most e x c i t i n g developments now appear. The new techniques of using pheremones and pheremones combined w i t h s e l e c t i v e i n s e c t i c i d e treatment i s a s i g n i f i c a n t advance. One looks a l s o f o r great advances i n the use of agents such as BT, and v i r u s e s f o r i n s e c t c o n t r o l . These agents, modified by genetic engineering, are l i k e l y t o be f a r more potent and s e l e c t i v e than those m a t e r i a l s c u r r e n t l y a v a i l a b l e . I t would seem reasonable a l s o , to see the number of d i f f e r e n t b i o l o g i c a l agents a v a i l a b l e increased i n the near f u t u r e .


1. FREED Historical Overview In the space of 40 y e a r s , tremendous advances have been made, not only i n f o r e s t pest management, but i n the way we view and manage t h i s v a l u a b l e resource. I t would seem unques t i o n a b l e that the chemical and b i o l o g i c a l agents w i l l play an ever i n c r e a s i n g r o l e to m a i n t a i n our f o r e s t s f o r a l l t h e i r v a r i e d purposes. The papers that we w i l l hear i n t h i s symposium can only c o n f i r m the great advances that have been made i n the use of these agents, and i n d i c a t e the even greater advances that can reasonably be expected i n the f u t u r e . Acknowledgments


This manuscript was issued as t e c h n i c a l paper no. 6905 from the Oregon A g r i c u l t u r a l Experiment S t a t i o n .

Literature Cited 1. Cope, J. Α.; Spaeth, J. N. J. For. 1931, 29, 775. 2. Fryer, J. D., J. Sci. 1955, 6, 73. 3. Afanasieu, M., Oklahoma Agricultural Experiment Station, Misc. Pub., NP-8. 4. Ahlgren, J. H.; Klingman, G. C.; Wolf, D. E. "Principles of Weed Control"; John Wiley and Sons: New York, 1951. 5. Robbins, W. W.; Crafts, A. S.; Raynor, R. N. "Weed Control"; McGraw H i l l : New York, 1952. 6. "Research Paper Number 13," Dahms, W. G.; James, G. Α., The U.S. Department of Agriculture Forest Service, Pacific N.W. Forest and Range Experiment Station, 1955. 7. "Effects of Certain Common Brush Control Techniques and Materials on Game Foods and Cover on a Power Line Right of Way," Bramble, W. C.; Byrnes, W. R., Pennsylvania State University Agricultural Experiment Station, 1955. 8. Chemical and Brush Control Techniques in California Rangelands," Leonard, O. Α.; Carlson, C. E., 1955. 9. Peevy, F. Α.; Campbell, R. S. J. For. 1949, 47, 443. 10. "Pest Control: An Assessment of Present and Alternative Technologies, Forest Pest Control," 4, National Academy of Science, 1975. 11. Newton, M.; Knight, F. B. "Handbook of Weed and Insect Control Chemicals for Forest Resource Managers"; Timber Press: Beaverton, Oregon. 12. " The Future of Insecticides: Needs and Prospects"; Metcalf, R. L.; McKelvey, J. J., Jr., Ed.; John Wiley and Sons: New York. RECEIVED

October 3, 1983


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Chemical and Biological Agents in Forest Pest Management - ACS

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