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I l l CONCLUSIONS AND RECOMMENDATIONS The f i n a l p l e n a r y s e s s i o n of the workshop, p r e s i d e d over by Dr Gerard A R o h l i c h , Chairman of the NAS panel, and Dr Dennis H I r v i n e , Chairman of the NSRC panel, adopted a statement of c o n c l u s i o n s and recommendations from the two working groups I t i s summarized below Conclusions No s i n g l e method of management or c o n t r o l w i l l be a panacea f o r Guyana's a q u a t i c weed problems, most b e n e f i c i a l to Guyana as a whole w i l l be a blend of d i f f e r e n t methods i n which the b e n e f i t s of each a r e maximized and i t s l i m i t a t i o n s minimized For example, h a r v e s t i n g weeds may be s a t i s f a c t o r y i n a c c e s s i b l e waterways where one s p e c i e s of p l a n t predominates, but i n l e s s a c c e s s i b l e waters, or i n those w i t h mixed stands, b i o l o g i c a l agents or h e r b i c i d e s may be p r e f e r a b l e I n other c a s e s e x i s t i n g stands may be too dense and woody f o r a b i o l o g i c a l agent to be e f f e c t i v e so the best approach may be to a t t a c k the stand e i t h e r by us i n g h e r b i c i d e s or by har- v e s t i n g and then to use a b i o l o g i c a l agent as a follow-up to keep down regrowth I n g e n e r a l , a l l methods of a q u a t i c p l a n t c o n t r o l complement each other and should not be considered competitors When a p p r o p r i a t e l y c o n t r o l l e d , a q u a t i c p l a n t s have many c o n s t r u c t i v e r o l e s i n the aq u a t i c environment 1 Producing oxygen . 2 Serving a s food, n e s t - b u i l d l n g m a t e r i a l , and s i t e s f o r egg attachment f o r a q u a t i c i n s e c t s and f i s h , - 5 -
3 P r o t e c t i n g s m a l l organisms from predation, 4 Converting s i l t and d i s s o l v e d n u t r i e n t s i n the waterway to p o t e n t i a l l y usable o r g a n i c matter, 5 Serving as food f o r b i r d s , f i s h , and land animals, and 6 Anchoring s o i l i n p l a c e B e n e f i t s are p r o p o r t i o n a l to p l a n t d e n s i t y to only a c e r t a i n l i m i t , when the p l a n t s form dense or e x t e n s i v e stands detriments outweigh bene- f i t s , and the p l a n t s become an economic burden Aquatic weed management should be aimed a t maximizing and c a p i t a l i z i n g on the b e n e f i t s the p l a n t s b r i n g to the country Thus, waterway c l e a r i n g should be conducted to an extent appropriate f o r f i s h i n g , p u b l i c h e a l t h , n a v i g a t i o n , drainage, and use of p l a n t s as a vegetable resource and water- p u r i f i c a t i o n t o o l These goals do not o f t e n c a l l f o r e r a d i c a t i n g the p l a n t s Moreover, few weed-control methods can destroy the r o o t s tubers, and rhizomes of submerged and emergent weeds buried m mud Such rooted s t r u c t u r e s can be reached only by a few animals that dig thei" out or by complex machinery At p r e s e n t , e r a d i c a t i o n of submerged aim emergent weeds i s almost i m p o s s i b l e Recommendations The f o l l o w i n g j o i n t recommendations emerged from the workshop 1 A con t i n u i n g comiaittee on a q u a t i c p l a n t management The N a t i o n a l Science Research C o u n c i l of Guyana should c r e a t e a continuing committee on a q u a t i c p l a n t management wi t h membership from a l l o r g a n i z a t i o n s that have a u t h o r i t y over, or are i n t e r e s t e d i n , the country's waterways - 6 -
2 A c t i o n to r e s t r i c t the i n t r o d u c t i o n of f o r e i g n a q u a t i c p l a n t s and the spread of e x i s t i n g s p e c i e s Guyana i s f o r t u n a t e not to have some of the a q u a t i c weeds that cause s e r i o u s economic problems elsewhere Guyana should i n s t i t u t e extreme e f f o r t s to p r o t e c t a g a i n s t the I n t r o d u c t i o n of any a q u a t i c v e g e t a t i o n t h a t could worsen the e x i s t i n g problem I n a d d i t i o n i t should take measures to prevent p l a n t s from spreading from i n f e s t e d to nonlnfested a r e a s w i t h i n Guyana 3 U t i l i z a t i o n of processed and unprocessed a q u a t i c weeds a) An engineer should be s e l e c t e d and made r e s p o n s i b l e f o r overseeing a p r o j e c t on h a r v e s t i n g a q u a t i c p l a n t s and us i n g the Bagnall P r e s s f o r pr o c e s s i n g them T h i s p r o j e c t w i l l a l s o r e q u i r e a f u l l - t i m e crew to h a r v e s t , chop, p r e s s , and t r a n s p o r t waterhyacinth p r e s s r e s i d u e Comparative data on the h a r v e s t i n g and pr o c e s s i n g of a l l the major a q u a t i c p l a n t s i n Guyana should be obtained The performance of the p r e s s and r e l a t e d equipment should be evaluated under a v a r i e t y of c o n d i t i o n s , m o d i f i c a t i o n s made, and operating procedures optimized Support equipment and improved or l a r g e r p r e s s e s may be designed, b u i l t , and t e s t e d , a s experience d i c t a t e s b) An animal n u t r i t i o n i s t should be appointed to oversee a p r o j e c t on the u t i l i z a t i o n of a q u a t i c p l a n t s i n c a t t l e and sheep d i e t s c) A s o i l s c i e n t i s t should be designated to run a p r o j e c t on the u t i l i z a t i o n of harvested a q u a t i c p l a n t s f o r s o i l improvement The purpose of t h i s p r o j e c t would be to e v a l u a t e p o t t i n g m a t e r i a l s made from water- h y a c i n t h â b o t h f r e s h whole p l a n t s and r e s i d u e from p r e s s i n g â i n combination w i t h m a t e r i a l s such as t r e e bark, wood shavings, r i c e h u l l s , p o u l t r y house - 7 -
l i t t e r , peat, sand, c l a y , and s u g a r m i l l r e s i d u e s Concurrently, a study should be I n i t i a t e d to measure the e f f e c t of adding the combinations to vegetable gardens planted i n the v a r i o u s s o i l types found throughout the country 4 T r i a l s w i t h h e r b l v o r l o u s f i s h L o c a l f i s h e r i e s s c i e n t i s t s should determine the p o t e n t i a l of c e r t a i n f i s h to s u r v i v e , grow, and c o n t r o l weeds i n d i f f e r e n t types of waterways i n Guyana One thousand young white amurs Ctenopharyngodon i d e l l a and an equal number of young T i l a p l a z l l l i l should be brought to the Guyana F i s h Hatchery f o r r e s e a r c h s t u d i e s under s t r i c t quarantine Both f i s h i n g e s t stems and f o l i a g e w i t h l i t t l e or no waste Both could e x p l o i t Guyana's crop of a q u a t i c weeds to produce n u t r i t i o u s meat th a t could c o n t r i b u t e to the Guyanese d i e t and might e v e n t u a l l y prove to be a commercially v a l u a b l e r e s o u r c e 5 Manatees T r i a l s to use manatees f o r p r a c t i c a l weed c o n t r o l m c a r e f u l l y s e l e c t e d c a n a l s , l a k e s , and permanant r e s e r v o i r s should be I n s t i t u t e d These t r i a l s would s e r v e to reawaken l o c a l i n t e r e s t i n t h i s method of weed c o n t r o l , which i s v i r t u a l l y unique to Guyana Furthermore, the r e l e v a n t a u t h o r i t i e s ' a t t e n t i o n should be drawn to the need to improve enforcement of the manatee p r o t e c t i o n laws a l r e a d y on the s t a t u t e books i n Guyana 6 B i o l o g i c a l c o n t r o l s a) Propagules of three s p e c i e s of s p i k e r u s h ( E l e o c h a r i s c o l o r a d o e n s l s , E a c l c u l a r i s , and E p a r v u l a ) should be brought to Guyana from the United - 8 -
S t a t e s and s t u d i e d under quarantine c o n d i t i o n s f o r t h e i r p o t e n t i a l to d i s p l a c e harmful weeds These p l a n t s grow c l o s e together and look l i k e underwater lawns They have been found to compete s u c c e s s f u l l y with rooted submersed a q u a t i c weeds by crowding out and d i s p l a c i n g neighboring a q u a t i c weeds and preventing the weeds from r e e n t e r i n g an a r e a where the "lawn" has been e s t a b l i s h e d b) Waterfowl can help remove v e g e t a t i o n from waterways T h e i r husbandry could become Important i n Guyana as a s e l f - s u p p o r t i n g a d j u n c t to conven- t i o n a l a q u a t i c weed management Waterfowl are e s p e c i a l l y e f f e c t i v e i n s m a l l ponds f o r the c o n t r o l of duckweed Though they w i l l have l i t t l e impact on the o v e r a l l weed problem, t h e i r production as a cottage I n d u s t r y should be encouraged c) Although the u t i l i z a t i o n of i n s e c t s as c o n t r o l s f o r a q u a t i c weeds i n Guyana i s remote, the waterhyacinth w e e v i l Neochatina e i c h h o r n i l , c u r - r e n t l y a l e a d i n g candidate f o r the b i o l o g i c a l c o n t r o l of w a t e r h y a c i n t h . I s found i n the i n t e r i o r of Guyana D e t a i l e d surveys a r e needed to confirm whether, as now thought, the w e e v i l s a r e absent from the c o a s t a l r e g i o n of Guyana I f they are absent, importing them from the i n t e r i o r or from Argentina may provide some waterhyacinth c o n t r o l 7 Chemical c o n t r o l C o n t r o l l i n g a q u a t i c weeds w i t h h e r b i c i d e s has proven e f f e c t i v e on sugar e s t a t e s i n Guyana However, the general problems i n u s i n g h e r b i c i d e s a r e made more d i f f i c u l t by the t u r b i d i t y of water i n Guyana, some of the s a f e s t h e r b i c i d e s a r e d e a c t i v a t e d on contact w i t h s i l t Although c o n s i d e r a b l e - 9 -
r e s e a r c h has been conducted on h e r b i c i d e r e s i d u e s , t h e i r l e v e l s and s a f e t y i n potable and i r r i g a t i o n waters i n Guyana needs to be determined more p r e c i s e l y A proposal was made that Guyana s e t up a p e s t i c i d e committee or a u t h o r i t y to monitor p e s t i c i d e l e v e l s i n water used f o r domestic purposes The workshop a l s o acknowledged that h e r b i c i d e s should not be considered a long-term s o l u t i o n and that i f adequate a l t e r n a t i v e c o n t r o l s can be found, t h e i r use should be encouraged 8 Aquatic weeds and h y d r o e l e c t r i c i t y development A l l e l e c t r i c power i n Guyana i s now produced i n thermal power s t a t i o n s , y e t many p o t e n t i a l l y v a l u a b l e h y d r o e l e c t r i c s i t e s e x i s t i n the i n t e r i o r , and schemes to u t i l i z e them are under c o n s i d e r a t i o n Because of the probable development of c o s t l y weed i n f e s t a t i o n s , h y d r o e l e c t r i c p l a n t s i n Guyana should i n c l u d e p r e v e n t i v e measures to ensure t h a t dammed water does not become i n f e s t e d with a q u a t i c weeds An I n t e r n a t i o n a l Manatee Research Center A separate recommendation emerged from the j o i n t panel to explore the p o s s i b i l i t y of e s t a b l i s h i n g an i n t e r n a t i o n a l manatee r e s e a r c h center i n Guyana Almost nothing i s known about the breeding h a b i t s and repro- duction of the manatee I t has never bred i n c a p t i v i t y , and a complete p h y s i o l o g i c a l and r e p r o d u c t i v e study i s needed i f i t s breeding i s to be understood Research i s u r g e n t l y r e q u i r e d to f i n d ways to s t i m u l a t e and speed up manatee reproduction so that what p r e s e n t l y i s a slow reproduc- t i v e process can be made more r e g u l a r and more productive - 10 -
Guyana i s a most l o g i c a l p l a c e to conduct t h i s r e s e a r c h The Caribbean manatee and the Amazonian manatee are both n a t i v e to Guyana Guyanese s c i e n t i s t s have had more experience with manatees than any ot h e r s , and the p h y s i c a l c o n d i t i o n s a r e i d e a l To o u t l i n e the best course of a c t i o n to begin a manatee biology r e s e a r c h f a c i l i t y i n Guyana, an i n t e r n a t i o n a l s t e e r i n g group should be e s t a b l i s h e d â¢11-
