SURVEY METHODS TO DETERMINE THE DISTRIBUTION AND INTENSITY OF DWARF MISTLETOES Oscar J . Dooling ^ L1 Abstract: Dwarf mistletoe distribution and intensity must be known to determine feasibility and priority of control measures. Surveys range from a quick estimate included in a general stand examination to a thorough investigation with large-scale maps. Accuracy and precision needed for management decisions will dictate which method to use. The 6-class system for rating dwarf mistletoe intensity is currently the best available for general use. INTRODUCTION The theme of this symposium is dwarf mistletoe control through forest management. Before something can be managed, you must know where it is. Because dwarf mistletoes are seed-producing plants with a limited spread potential, their occurrence tends to be spotty and concentrated, not random. It is not only important to know where dwarf mistletoes are, but also where they are not. If a significant portion of a stand is dwarf mistletoe-free, your options are broader. Conversely, if the stand is heavily infested, your options may be limited to either doing nothing or destroy- ing the stand and starting over. Knowing the distribution of dwarf mistletoe will help you determine the feasibility or priority of a proposed action. Knowing the infection intensity is also important. A light infection does not have a measurable impact on tree or stand growth, but a heavy infection can reduce potential volume to as little as one-seventh, or 14 percent, y that of a healthy stand (On and Dooling 19691.'^/presented at Symposium on Dwarf Mistletoe Control Through Forest Management, Berkeley, Calif. April 11-13, 1978. LI~lantPathologist, Forest Insect and Disease Management, Forest Service, U.S. Department of Agriculture, Missoula, Montana. ' o n , D., and O.J. Dooling. 1969. A study of the effect of dwarf mistletoe infection on the growth of western larch. USDA Forest Serv., 7 p. Northern Region, Missoula, Mont. Intensity rating systems are used to quantify degree of infection for management priority determinations, to quantify growth loss and mortality, to help define suitable seed trees, and to help quantify infection hazard of over- story trees to understory stands (Hawksworth 1977). Infection intensities are also required as inputs for yield simulation models (Myers and others 1976, Myers and others 1971). DISTRIBUTION SURVEYS The simplest and least expensive survey is one included as part of stand examinations. The number of sample points is necessarily limited, and may give neither the accuracy nor precision required for good management planning. At the other end o f t h e scale is a complete cruise with accurate mapping of all infected trees and infection centers. Either method may be necessary in specific circum- stances, but normally something in between these extremes will provide the desired accu- racy and precision at a reasonable cost. Extensive surveys, designed to give the overall distribution over large areas can be either random or systematic. Graham (1964) determined the distribution of Arceuthobium douglasii in Douglas-fir, A. americanum in lodgepole pine, and A. laricis in western larch in western Montana by sampling townships at 10 locations. He predetermined the start of a line from a point on the road nearest the center of each township and spaced his plots at 10-chain intervals along the line. At each plot, he gathered data on infection from three concentric circular areas: 115- a c r e f o r sawtimber, 1/50-acre and 1 / 5 0 0 - a c r e f o r s a p l i n g s . for pole sized, I n a s m a l l e r a r e a , Brown (1976) g a t h e r e d d a t a o n d i s t r i b u t i o n o f A. americanum i n lodgep o l e p i n e w i t h a s a m p l i n g t e c h n i q u e t h a t gave a n i n t e n s i t y o f one p l o t f o r e v e r y 1 0 a c r e s . He t o o k a s t r a t i f i e d sample c o n s i s t i n g o f a p r i s m p l o t f o r t h e o v e r s t o r y and a 1 / 1 0 0 - a c r e c i r c u l a r p l o t f o r t h e u n d e r s t o r y a t e a c h sample point. He examined t r e e s o n l y f o r p r e s e n c e o r a b s e n c e o f dwarf m i s t l e t o e . I n conjunction with a roadside s t r i p surv e y o f A. americanum i n l o d g e p o l e p i n e , Hawksw o r t h (1958) e s t a b l i s h e d s t a r t i n g p o i n t s mec h a n i c a l l y a l o n g r o a d s and d e s i g n a t e d two p a r a l l e l l i n e s a t l e a s t one m i l e l o n g f o r s a m p l i n g . D i s t a n c e between l i n e s was random, b u t was n o t l e s s t h a n 20 o r more t h a n 40 c h a i n s . He examined e i g h t c i r c u l a r 1 / 1 0 - a c r e p l o t s p e r m i l e f o r p r e s e n c e and i n t e n s i t y of dwarf m i s t l e t o e infection. I n a s u r v e y o f A. v a g i n a t u m s u b s p . wtopodum i n p o n d e r o s a p i n e , Hawksworth (1956) g a t h e r e d d a t a on p r e s e n c e and i n t e n s i t y o f dwarf m i s t l e t o e f r o m s i x random p l o t s p e r m i l e a l o n g p a r a l l e l l i n e s s p a c e d a t 112-mile i n t e r vals. C a h i l l (1973) r e c o r d e d p r e s e n c e o r a b s e n c e of A. americanum i n l o d g e p o l e p i n e on p l o t s a t f i v e - c h a i n i n t e r v a l s a l o n g l i n e s s p a c e d one m i l e a p a r t . He a l s o r a t e d t r e e s f o r i n f e c t i o n intensity. B o u r c h i e r (1956) c r u i s e d s t r i p s one c h a i n wide s p a c e d a t 1 0 - c h a i n i n t e r v a l s f o r p r e s e n c e o r a b s e n c e o f A. americanum i n l o d g e p o l e p i n e . A survey designed o r i g i n a l l y f o r determining w h i t e p i n e b l i s t e r r u s t i n c i d e n c e ( C l u t t e r 1966) 51 was m o d i f i e d by Toko and C a r l s o n (1968) t o d e t e r m i n e p r e s e n c e and i n t e n s i t y o f Arceuthobium s p p . The d e s i g n i s a t r e e c l u s t e r double-sampling t e c h n i q u e ; t h e f i r s t p a r t i s a " h a s t y " e x a m i n a t i o n , t h e second i s a " d e t a i l " e x a m i n a t i o n . The h a s t y e x a m i n a t i o n c o n s i s t s o f i n s p e c t i n g t r e e s o n l y f o r p r e s e n c e of i n f e c t i o n from which t n e p r o p o r t i o n o f i n f e c t e d stems i s estimated. The a u t h o r s s e l e c t e d and examined t h r e e d e t a i l t r e e s p e r c l u s t e r t o det e r m i n e number and l o c a t i o n o f i n f e c t i o n s . W a l t e r s and Brow. (1973) and Brown (1973) compared t h r e e s a m p l i n g t e c h n i q u e s f o r d e t e r ^clutter, J.L. 1966. A p r e l i m i n a r y sampling design f o r a white pine b l i s t e r r u s t i n c i d e n c e s u r v e y . 1 7 p. Univ. Ga., A t h e n s , Ga . m i n i n g p r e s e n c e and i n f e c t i o n i n t e n s i t y o f A. americanum i n l o d g e p o l e p i n e : t h e S t a g e I1 compartment e x a m i n a t i o n used i n t h e Rocky Mount a i n Region, a one-percent f i x e d p l o t sample, and t h i r d n e a r e s t t r e e sample on two- and f o u r c h a i n g r i d s . An a n a l y s i s o f t h e i r d a t a compared t o a c o m p l e t e c r u i s e showed t h a t a m o d i f i e d t h i r d n e a r e s t t r e e sample u s i n g a f o u r - c h a i n spacing w i l l give acceptable p r e c i s i o n a t a r e a s o n a b l e c o s t . The sample p o i n t i s a v a r i a b l e s i z e p l o t w i t h a maximum r a d i u s of 33 f e e t . Each p l o t i s d i v i d e d i n t o f o u r q u a d r a n t s by t h e i n t e r s e c t i o n of a b a s e l i n e t h r o u g h t h e p l o t c e n t e r a t r i g h t a n g l e s t o t h e compass l i n e . Q u a d r a n t s a r e examined i n a c l o c k w i s e d i r e c t i o n a r o u n d p l o t c e n t e r . The m o d i f i e d t h i r d n e a r e s t t r e e c o n s i s t s of a n e x a m i n a t i o n of o n l y t h e t h i r d n e a r e s t h o s t t r e e from t h e p l o t cent e r i n e a c h q u a d r a n t f o r a maximum of o n l y f o u r t r e e s p e r sample p o i n t . W a l t e r s and Geils (1977) h a v e m o d i f i e d t h e four-chain g r i d t o an eight-chain g r i d f o r d e t e r m i n i n g d i s t r i b u t i o n of A. v a g i n a t u m s u b s p . cryptopodum i n p o n d e r o s a p i n e . A l l o t h e r det a i l s are identical. Hawksworth (1956, 1958) t r a v e r s e d a l l p a s s a b l e r o a d s t h r o u g h s e v e r a l Ranger D i s t r i c t s by motor v e h i c l e a t l e s s t h a n 1 0 m i l e s p e r h o u r . He r e c o r d e d t y p e o f s t a n d , s i z e c l a s s , and i n t e n s i t y of dwarf m i s t l e t o e f o r a s t r i p on t h e r i g h t s i d e of t h e r o a d . S t r i p width v a r i e d w i t h t h e t y p e of s t a n d : o n e c h a i n i n old-growth and c u t o v e r s t a n d s , and 1 1 2 - c h a i n i n p o l e s t a n d s . He r e c o r d e d d i s t a n c e s t o t h e n e a r e s t 0 . 0 5 m i l e whenever c h a n g e s o c c u r r e d i n t y p e of s t a n d o r d e g r e e o f i n f e c t i o n . He h a s used t h i s t e c h n i q u e f o r A. d o u g l a s i i i n D o u g l a s - f i r , A, v a g i n a t u m s u b s p . cryptopodum micro.carpum i n s p r u c e , i n ponderosa p i n e , and A. americanum i n l o d g e p o l e p i n e . A. S i m i l a r r o a d s i d e s u r v e y s were u s e d i n other l o c a l i t i e s f o r determining d i s t r i b u t i o n and i n t e n s i t y of A. d o u g l a s i i i n D o u g l a s - f i r , A. -l a r i c i s i n w e s t e r n l a r c h , and A. americanum i n l o d g e p o l e p i n e (Graham 1 9 5 9 , 1 9 6 0 ; Graham and F r a z i e r 1962; Doidge 1 9 7 3 a , 1 9 7 3 b ) . S e v e r a l t y p e s of dwarf m i s t l e t o e / h o s t i n f e c t i o n s a r e e a s i l y recognized from t h e a i r : A . campylopodum i n p o n d e r o s a p i n e (Anon. 1 9 5 8 , 1 9 7 6 ) ; A. d o u g l a s i i i n D o u g l a s - f i r (Anon. 1 9 5 8 , 1976; Aho and Anderson 1 9 5 9 ; Hopkins 1 9 5 9 ) ; A. v a g i n a t u m s u b s p . cryptopodum i n p o n d e r o s a p i n e (Anon. 1 9 7 6 ) ; and A. americanum i n l o d g e p o l e p i n e (Anon. 1 9 7 6 , Baranyay and B o u r c h i e r 1 9 6 1 ) . Both a i r p l a n e s and h e l i c o p t e r s c a n be u s e d . L o c a t i o n s of v i s i b l e i n f e c t i o n s a r e s k e t c h e d o n t o maps o f s u i t a b l e s c a l e . The Canadian Forestry Service designed an integrated tapelevent recorder for aerial dis- tribution surveys of A. pusillum in jack pine (Robins 1972, Anon. 1973a, Ives and others 1973). The equipment consists of a four chan- nel event recorder, a tape recorder, control boxes, and headsets for two observers, a nav- igator, and the pilot. They use an airplane at 500 feet above ground and 100 miles per hour. Observers record dwarf mistletoe in- fections at right angles to the airplane on the event recorder and make comments on the tape recorder. The navigator insures proper course, altitude, and speed, and indicates start, intermediate, and finish flight line check points on the event recorder, base map, and tape recorder. Infection occurrence is transferred event recorder to map by a adjusted to match event tape Map-0-Graph scale to map scale. Relevant verbal Comments are also transferred to the map. @' In some parasite/host combinations, dwarf mistletoe-caused mortality results in circular openings in the canopy easily visible on con- ventional vertical aerial photographs: A. Esillum in black spruce (Anderson 1949, Meyer and French 1966, Murtha 1972) and A. americanurn in jack pine (Murtha 1972, Anon. 1973b, Muir and Robins 1973). The appearance of these openings on the photographs have been described as "moth-eaten" (Anderson 1949) or "ringworm- like" (Murtha 1972). Scales of 1:15,840 to 1:31,680 are usable (Muir and Robins 1973). On western pines, large-scale photography taken at a low oblique angle has shown promise for detecting brooming within crowns in open- grown stands (Heller and Bega 1973). Infra-red (false color) film for aerial detection of dwarf mistletoe was used at least as early as 1963 when Baranyay (1963) showed that A. americanum in lodgepole pine appeared as darkened areas in oblique, across valley photographs. He could not illustrate adequate shade differences between healthy and infected patches of trees on vertical photography (Baranyay 1968). Infra-red aerial photography has been successfully used to detect mortality in black spruce caused by A. pusillum (Meyer and French -'./Aspecial projector used in mapmaking when changing scale. 'Anderson, R.L. 1949. Black spruce dwarf mistletoe in Minnesota. Masters Thesis, 139 p. Univ. Minn., Minneapolis, Minn. 1967, Douglas 1973, I/ Douglas and others 1972, French and others 1975). In addition to old infection centers with mortality, young in- fection centers in which only brooming has occurred are also detectable (Meyer and French 1967, Douglas and others 1972). Photography scales from 1:30,000 (French 71 and others 1975) to 1:118,000 (Douglas 1973) are useful for detecting A. pusillum-caused openings as small as 0.1 acre in black spruce. Openings of 0.25 acre are visible at a scale of 1:462,000 (Douglas 1973). Dooling and others (1977) used a 3-person crew to examine and map the complete distri- bution of A. americanum in lodgepole pine in two sale areas in Montana. The survey crew consisted of a leader and two observers. The crew leader recorded presence of dwarf mistle- toe as determined by the observers (based on presence of plants, swellings, or brooms). Each observer covered a strip two chains wide. Distribution surveys range from simple to complex in design, and from reasonable to nearly prohibitive in cost. All these methods have valid uses. Tree species, stand structure, and proposed management action, along with accuracy and precision needed, will dictate which method to use. INFECTION INTENSITY RATING SYSTEMS There have been many attempts to quantify dwarf mistletoe infection on a tree basis (table 1) (Hawksworth 1977). Some systems have as few as four classes and one as many as 18. The terms "light ," "medium," and "heavy" have been used in many rating systems, but have not been very well defined. The 6-class dwarf mistletoe rating system, introduced by Hawksworth and Lusher (1956) is now the accepted standard in the Western United States and Western Canada. Hawksworth (1977) has recently discussed the 6-class system in detail and described its uses and limitations. For the 6-class system, the live crown is divided into thirds, and each third is rated as: 0, no mistletoe; 1, light mistletoe (less than half of the branches infected); and 2, "Douglas,. R.W. 1973. Use of high altitude photography for forest disease detection and vegetation classification within the sub-boreal 'forest region. PhD Thesis, 141 p. Univ. Minn., Minneapolis, Minn. T a b l e 1--Rating s y s t e m s u s e d f o r dwarf m i s t l e t o e i n f e c t e d t r e e s (Hawksworth 1 9 7 7 ) . Arceuthobium species (and h o s t ) A. -l a r i c i s (western l a r c h ) -- Number o f Classes (including healthy) Description Reference 0, h e a l t h y t r e e s ; i n f e c t e d r a t e d X , XX, XXX, o r XXXX b a s e d o n d e g r e e of i n f e c t i o n ( n o t d e f i n e d ) . Weir 1916 vaginatum subsp. topodum (ponderosa pine) 0, healthy t r e e s without mistletoe; X, l i g h t m i s t l e t o e infection; XX, medium m i s t l e t o e i n f e c t i o n ; XXX, heavy m i s t l e t o e i n f e c t i o n . K o r s t i a n and Long 1922 A. americanum (jack pine) 0, h e a l t h y t r e e ; X , s l i g h t l y inf e c t e d t r e e ; XX, s e v e r e l y i n f e c t e d t r e e ; XXX, v e r y b a d l y broomed tree. Dowding 1929 A. d o u g l a s i i (Douglas-f i r ) and A. v a g i n a t u m s u b s p . cryptopodum (ponderosa p i n e ) . S i x - c l a s s s y s t e m . Each t h i r d of l i v e crown r a t e d a s 0 , no m i s t l e t o e ; 1, l e s s t h a n h a l f t h e b r a n c h e s I n f e c t e d ; o r 2 , more t h a n h a l f t h e branches infected. Ratings of each t h i r d t o t a l e d . R a t i n g s r a n g e from 0 (uninfected t r e e ) t o 6 (heavily infected). Hawksworth and Lusher 1956, Hawksworth 1 9 6 1 A. d o u g l a s i i (Douglas-f i r and A. l a r i c i s (western l a r c h ) . "None" - no v i s i b l e i n f e c t i o n ; "Light" - l e s s t h a n o n e - t h i r d o f crown broomed; "Medium" one t o two t h i r d s o f crown broomed; 'Heavy" - more t h a n t w o - t h i r d s o f crown broomed P i e r c e 1960 A. d o u g l a s i i (Douglas-f i r ) C l a s s I - no e v i d e n c e of brooming; C l a s s I1 - brooming c o n f i n e d t o lower t h i r d of crown; C l a s s I11 - brooming f o r a t l e a s t twot h i r d s of l i v e crown; C l a s s I V brooming f o r a t l e a s t t w o - t h i r d s o f l i v e crown, and s p i k e t o p developing. Shea 1 9 6 3 Arceuthobium spp, (several hosts i n western Montana) L i v e crown d i v i d e d i n t o 2 e q u a l p a r t s , e a c h h a l f was r a t e d a s 0 , no i n f e c t i o n ; 1, l e s s t h a n onet h i r d of branches i n f e c t e d ; o r 2 , more t h a n o n e - t h i r d o f b r a n c h e s i n f e c t e d . T o t a l f o r each h a l f of crown added f o r t h r e e t o t a l s which r a n g e from 0 (no i n f e c t i o n ) t o 4 ( v e r y heavy i n f e c t i o n ) . Graham 1964 A. - 5 - . T a b l e I--Rating systems used f o r dwarf m i s t l e t o e i n f e c t e d t r e e s (Hawksworth 1977) ( c o n t i n u e d ) . Arceuthobium species (and h o s t ) Arceuthobium spp. (several h o s t s i n NE Washington) Number of Classes (including healthy) Description Reference Same a s a b o v e , b u t w i t h 1 a d d i tional class for trees killed w i t h i n t h e p r e v i o u s 5 y e a r s and showing symptoms o r s i g n s of having had dwarf m i s t l e t o e . Graham and F r a z i e r 1962 A. - tsugense (western hemlock) Each t h i r d of crown r a t e d from 0.0 (no v i s i b l e i n f e c t i o n s ) t o 3 . 0 (numerous l a r g e b r a n c h i n f e c t i o n s i n t h e form of w i t c h e s ' brooms and a t l e a s t 1 t r u n k s w e l l i n g ) by 0 . 5 c l a s s i n t e r v a l s . Rating i n each t h i r d t o t a l e d for tree ratings. Smith 1969 A. t s u g e n s e (western hemlock) M i d d l e - t h i r d r a t i n g system. Because t h e lower t h i r d of t h e t r e e o f t e n had numerous d e a d , broken, and m i s s i n g b r a n c h e s and because t h e t o p t h i r d was o f t e n p a r t i a l l y hidden, an analy s i s of growth l o s s i n r e l a t i o n t o t h e middle-third r a t i n g only was made. The r e s u l t s s u g g e s t t h a t middle-third r a t i n g i s superior t o whole-tree r a t i n g . Smith 1969 A . americanum (lodgepole pine) 0 , h e a l t h y ; 1, l i g h t b r a n c h i n f e c t i o n , l e s s t h a n 50% of crown i n f e c t e d ; 2, heavy branch and stem i n f e c t i o n , more t h a n 50% of t h e crown i n f e c t e d ; 3, w i t c h e s ' brooms, branch and stem i n f e c t i o n s , more t h a n 50% of t h e crown i n f e c t e d . Baranyay and S a f r a n y i k 1970 A. a b i e t i n u m (true f i r s ) Each t h i r d of crown r a t e d a s 0 , no m i s t l e t o e ; 1, 1-10% of b r a n c h e s i n f e c t e d ; 2 , 11-50% of b r a n c h e s i n f e c t e d ; and 3 , over 50% of b r a n c h e s i n f e c t e d . T o t a l s added f o r t r e e r a t i n g . Note t h a t by combining c l a s s e s 1 and 2 i n e a c h t h i r d , r a t i n g s a r e t h e same a s i n t h e 6 - c l a s s system. Scharpf 1977 6 heavy mistletoe (more than half of the branches infected). The ratings of each third are added to obtain a total for the tree. For example, a tree heavily infected in the lower third of the crown, lightly infected in the middle third, and not infected in the upper third, would be Class 3 (fig. 1). A tree heavily infected in each third would be Class 6. The system is simple to use, and different observ- ers tend to rate an infected tree similarly. A tree with an infection on the bole, but not the branches, is rated as Class 1. Otherwise, bole infections are not considered in the rating system. The 6-class system was originally used for A. vaginatum subsp. cryptopodum in ponderosa pine and for A. douglasii in Douglas-fir in the Southwest (Hawksworth and Lusher 1956, Andrews and Daniels 1960, Hawksworth 1961). It was later found to be applicable to 4. icanum in lodgepole pine in the Central Rockies (Hawksworth and Hinds 1964, Myers and others 1971). The system has also been applied to A. campylopodum in ponderosa pine in the Pa- =- cific Northwest (Shea 1964, Flora 1966), A. occidentale in digger pine in California (Hawksworth 1969), and A. cyanocarpum on limber pine in Colorado (Hawksworth and others 1975). The 6-class system is also being widely used in Western Canada: A. americanum in lodgepole pine (Dobie and Britneff 1975), A. in western hemlock and shore pine (Smith and Wass 1976), and Arceuthobium spp. (Baran- yay and Smith 1972). *- Of the 12 rating systems proposed, the 6-class system is most widely used. It is being used for several hostlparasite combina- tions in the Western United States and Canada. The 6-class system has been used for many purposes: to quantify height and diameter- growth loss in infected trees, to quantify in- fection in stands, and to select seed trees. The system does have limitations and may not be applicable to all hostlparasite combinations, but it does have the strong attribute of com- parability and seems to be the best currently available system for general use. EXAMPLE INSTRUCTIONS STEP 1, DIVIDE LIVE CROWN I STEP 2, RATE EACH THIRD EACH THIRD SEP SHOULD BE GIVEN RATING OF 0, 1, OR 2 AS DESCRIBED BELOW, (0) V I S I B L E INFECTIONS, (1) LIGHT (1/2 (2) HEAVY INFECTION THAN 1/2 OF TOTAL (MORE INFECTION LESS OF TOTAL NUMBER OF BRANCHES I N THE T H I R D INFECTED), OR IFT H I S A T H I R D HAS NO V I S I B L E INFECTIONS, I T S RATING I S (01, ------- ---- T H I R D IS L I G H T L Y INFECI T S RATING I S (1). - -- - - - ---- IF THIS THIRD I S HEAVILY FECTEDj I T S RATING I S ( NUMBER OF BRANCHES I N THE TH IRD INFECTED), STEP 3, FINALLY, ADD RATINGS OF THIRDS TO OBTAIN RATING FOR TOTAL TREE, THE TREE IN THIS EXAMPLE W I L L R E C E I V E A RATING OF 0 + 1 + 2 = ~ , Figure I--Instructions and example of the use of the 6-class mistletoe rating system (Hawksworth 1961, 1977). LITERATURE CITED Aho, P.E., and L.N. Anderson 1959. D o u g l a s - f i r dwarf m i s t l e t o e a e r i a l s u r v e y , Rouge R i v e r N a t i o n a l F o r e s t 1958. USDA F o r e s t S e r v . , P a c i f i c Northwest Fore s t and Range Exp. S t n . , P o r t l a n d , Oreg. 12 p. Andrews, S.R., and J . P . D a n i e l s 1960. A survey of dwarf m i s t l e t o e s i n A r i zona and New Mexico. USDA F o r e s t S e r v . , Rocky Mountain F o r e s t and Range Exp. Stn., S t n . Pap. 49, 17 p . , F o r t C o l l i n s , Colo. Anonymous 1958. Annual Report 1957. USDA F o r e s t S e r v . , P a c i f i c Northwest F o r e s t and Range Exp. S t n . , P o r t l a n d Oreg., p.62-63. Anonymous 1973a. A dwarf m i s t l e t o e survey t e c h n i q u e . Can. F o r e s t S e r v . , Northern F o r e s t Res. C e n t r e , A l b e r t a , Can., For. Rept. 3 ( 2 ) : 7 . Anonymous 1973b. Dwarf m i s t l e t o e damage. Can. F o r e s t Serv.,Northern F o r e s t Res. C e n t r e , A l b e r t a , Can., For. Rept. 3 ( 3 ) : 8 . Anonymous 1976. F o r e s t i n s e c t and d i s e a s e c o n d i t i o n s i n t h e I n t e r m o u n t a i n S t a t e s d u r i n g 1975. USDA F o r e s t S e r v . , I n t e r m o u n t a i n Region, Ogden, Utah, 1 2 p. Baranyay, J.A. 1963. D e t e c t i o n of dwarf m i s t l e t o e - i n f e c t e d s t a n d s by a e r i a l photography. Ann. Rept., For. Entomol. and P a t h o l . Branch, Can. Dep. For., Calgary, A l b e r t a , Can., 138 p. Baranyay, J . A . 1968. Experiment w i t h a e r i a l c o l o r photography f o r d e t e c t i n g dwarf m i s t l e t o e i n f e s t e d l o d g e p o l e p i n e s t a n d s i n t h e Alb e r t a T e r r i t o r i e s Region. F o r e s t Res. Lab., C a l g a r y , A l b e r t a , Can., I n t e r n a l Rep o r t . A-12, 35 p. Baranyay, J . A . , and R . J . Bourchier 1961. P r o v i n c e of A l b e r t a f o r e s t d i s e a s e s u r v e y . 1960 Annu. Rept. For. I n s . and Dis. Survey. Can. F o r e s t S e r v . , p. 88-92. Baranyay, J . A . , and L. S a f r a n y i k 1970. E f f e c t of dwarf m i s t l e t o e on growth and m o r t a l i t y of l o d g e p o l e p i n e s t a n d s i n A l b e r t a . Can. Dep. F i s h and F o r . Publ. 1285, 1 9 p . Baranyay, J . A . , and R.B. Smith 1972. Dwarf m i s t l e t o e s i n B r i t i s h Columbia and recommendations f o r t h e i r c o n t r o l . Can. F o r e s t Serv. Rept. BC-X-72, 1 8 p . B o u r c h i e r , R.J. 1956. Province of A l b e r t a , f o r e s t d i s e a s e survey. Div. of For. Bio. I n s . and D i s . Survey Annu. Rept. 1955, p . 89-91 Calg a r y , A l b e r t a , Can. Brown, D.H. 1973. An e v a l u a t i o n survey p r o c e d u r e f o r dwarf m i s t l e t o e i n proposed t h i n n i n g proj e c t s . USDA F o r e s t S e r v . , Rocky Mountain Region, 6 p. Lakewood, Colo. Brown, D.H. 1976. B i o l o g i c a l e v a l u a t i o n , dwarf m i s t l e t o e - Arapaho and Roosevelt N a t i o n a l Fore s t s , R e d f e a t h e r Ranger D i s t r i c t , 1974. USDA F o r e s t S e r v . , Rocky Mountain Region Rept. R2-76-1, 7 p. Lakewood, Colo. C a h i l l , D.B. 1973. Impact e v a l u a t i o n , mountain p i n e b e e t l e and dwarf m i s t l e t o e , D i l l o n Rese r v o i r . USDA F o r e s t S e r v . , Rocky Mountain Region Timber Manage. Rept. R2-73-19,24p. Lakewood, Colo. Dobie, J . , and A.A. B r i t n e f f 1975. Lumber g r a d e s and volumes from lodgep o l e p i n e i n f e c t e d w i t h dwarf m i s t l e t o e . Wood and F i b e r 7:104-109. Doidge, D.F. 1973a. Annual d i s t r i c t r e p o r t f o r e s t i n s e c t and d i s e a s e s u r v e y , B r i t i s h Columbia, 1972, P a r t V I , Caribou F o r e s t D i s t r i c t . Can. F o r e s t S e r v . , P a c i f i c F o r e s t Res. C e n t r e I n f o . Rept. BC-X-77, 22 p. V i c t o r i a , B.C., Can. Doidge, D.F. 1973b. F o r e s t i n s e c t and d i s e a s e c o n d i t i o n s , 1973, Caribou D i s t r i c t . Can. F o r e s t S e r v . P a c i f i c F o r e s t Res. C e n t r e I n f o . Rept. BC-X-96, 1 0 p. V i c t o r i a , B. C . , Can. Dooling, O . J . , J . D . B o r t z , and M.W. Maxwell 1977. Dwarf m i s t l e t o e s u r v e y , Hebgen Lake Ranger D i s t r i c t , G a l l a t i n N a t i o n a l F o r e s t , Montana. USDA F o r e s t S e r v . , Northern Reg i o n Rept. 77-13, 5 p. M i s s o u l a , Mont. Douglas, R.W., M.P. Meyer, and D.W. French 1972. Remote s e n s i n g a p p l i c a t i o n s t o f o r e s t v e g e t a t i o n c l a s s i f i c a t i o n and coni f e r v i g o r l o s s due t o dwarf m i s t l e t o e . NASA E a r t h R e s o u r c e s Survey Program, F i n a l R e p t . , 9 1 p. Univ. C a l i f . , B e r k e l e y , Calif. Dowding, E.S. 1929. The v e g e t a t i o n o f A l b e r t a 111. The s a n d h i l l a r e a s of c e n t r a l A l b e r t a w i t h p a r t i c u l a r r e f e r e n c e t o t h e ecology of Arceuthobium americanum N u t t . J. E c o l . 17:82-105. F l o r a , D.F. 1 9 6 6 . A method o f f o r e c a s t i n g r e t u r n s f r o m p o n d e r o s a p i n e dwarf m i s t l e t o e c o n t r o l . USDA F o r e s t S e r v . , P a c i f i c Northwest Fore s t and Range Exp. S t n . Res. Pap. PNW-32, 1 7 p . P o r t l a n d , Oreg. F r e n c h , D . , M. Meyer, and F. I r v i n g 1975. A p p l i c a t i o n o f r e m o t e s e n s i n g t o det e c t i o n and c o n t o l o f dwarf m i s t l e t o e i n b l a c k s p r u c e s t a n d s . Univ. Minn., Remote S e n s i n g Lab. Res. R e p t . 75-4, 11 p. Minn e a p o l i s , Minn. Graham, D.P. 1959. Dwarf m i s t l e t o e s u r v e y i n K o o t e n a i N a t i o n a l F o r e s t . USDA F o r e s t S e r v . , I n t e r m o u n t a i n F o r e s t and Range Exp. S t n . Res. Note 67, 5 p . Ogden, Utah. Graham, D.P. 1960. Dwarf m i s t l e t o e s u r v e y i n Kaniksu N a t i o n a l F o r e s t . USDA F o r e s t S e r v . , I n t e r m o u n t a i n F o r e s t and Range Exp. S t n . Res. Note 7 4 , 6 p. Ogden, Utah. Graham, D.P. 1964. Dwarf m i s t l e t o e s u r v e y i n w e s t e r n Montana. USDA F o r e s t S e r v . , I n t e r m o u n t a i n F o r e s t and Range Exp. S t n . Res. Note INT4 , 7 p . Ogden, Utah. Graham, D.P., and W.E. F r a z i e r 1962. Dwarf m i s t l e t o e s u r v e y i n n o r t h e a s t e r n Washington. USDA F o r e s t S e r v . , Intermount a i n F o r e s t and Range Exp. S t n . Res. Note 1 0 3 , 8 p. Ogden, Utah. Havksworth, F.G. 1956. Region 3 dwarf m i s t l e t o e s u r v e y , prog r e s s r e p o r t o f t h e 1954-55 f i e l d work. USDA F o r e s t S e r v . , Rocky Mountain F o r e s t and Range Exp. S t n . Spec. R e p t . , 5 p . F o r t C o l l i n s , Colo. Hawksworth, F.G. 1958. Survey o f l o d g e p o l e p i n e dwarf m i s t l e t o e on t h e R o o s e v e l t , M e d i c i n e Bow, and Bighorn N a t i o n a l F o r e s t s . USDA F o r e s t S e r v . , Rocky Mountain F o r e s t and Range Exp. S t n . Pap. 35, 1 3 p. F o r t C o l l i n s , Colo. Hawksworth, F.G. 1961. Dwarf m i s t l e t o e of p o n d e r o s a p i n e i n t h e S o u t h w e s t . U.S. Dep. A g r i c . Tech. B u l l . 1246, 1 1 2 p. Hawksworth, F.G. 1969. Rapid i n t e n s i f i c a t i o n a n d upward s p r e a d of dwarf m i s t l e t o e i n i n o c u l a t e d d i g g e r p i n e s . P l a n t D i s . R e p t . 53:615-617. Hawksworth, F.G. 1977. The 6 - c l a s s dwarf m i s t l e t o e r a t i n g s y s t e m . USDA F o r e s t S e r v . , Rocky Mountain F o r e s t and Range Exp. S t n . Gen. T e c h . R e p t . RM-48, 7 p. F o r t C o l l i n s , Colo. Hawksworth, F.G., J.T. F i s h e r , and R.L. Mathiasen 1975. An u n u s u a l o c c u r r e n c e of Arceuthobium cyanocarpum on p o n d e r o s a p i n e n e a r B o u l d e r , Colorado. P l a n t D i s . R e p t . 59:758-759. Hawksworth, F.G., and T.E. Hinds 1964. E f f e c t s o f dwarf m i s t l e t o e on immature lodgepole p i n e s t a n d s i n Colorado. J. F o r . 62:27-32. Hawksworth, F.G., and A.A. L u s h e r 1956. Dwarf m i s t l e t o e s u r v e y and c o n t r o l on t h e M e s c a l e r o Apache R e s e r v a t i o n , New Mexico. J . F o r . 54:384-390. H e l l e r , R.C., and R.V. Gega 1973. D e t e c t i o n of f o r e s t d i s e a s e s by r e mote s e n s i n g . J . F o r . 71:18-21. Hopkins, H.G. 1959. S a l v a g i n g m i s t l e t o e damaged t i m b e r . P r o c e e d i n g s , West. F o r . Conf., 1 9 5 8 , p. 36-39. I v e s , W.G., J.J. Lawrence, and J.K. R o b i n s 1973. P r a i r i e s Region f o r e s t i n s e c t and d i s e a s e s u r v e y Annu. Rept., 1972, p . 74-81. Can. Dep. E n v i r o n . K o r s t i a n , C.F., and W.H. Long 1922. The w e s t e r n y e l l o w p i n e m i s t l e t o e : e f f e c t on growth and s u g g e s t i o n s f o r cont r o l . U.S. Dep. A g r i c . Tech. B u l l . 1 1 1 2 , 35 p . Meyer, M.P., and D.W. F r e n c h 1966. Dwarf m i s t l e t o e i n b l a c k s p r u c e f o r e s t s can be assessed through s e q u e n t i a l a e r i a l p h o t o g r a p h y . Photogramm. Eng. 32:812-814. Meyer, M.P., and D.W. F r e n c h 1967. D e t e c t i o n of d i s e a s e d t r e e s . gramm. Eng. 33:1035-1040 Photo- Muir, J.A., and J.K. Robins 1973. Detection of dwarf mistletoe of jack pine on aerial photographs. Plant Dis. Rept. 57:951-954. Murtha, P.A. 1972. A guide to air photo interpretation of forest damage in Canada. Can. Forest Serv. Publ. 1292, 62 p. Myers, C.A., F.G. Hawksworth, and J.L. Stewart 1971. Simulating yields of managed, dwarf mistletoe-infected lodgepole pine stands. USDA Forest Serv., Rocky Mountain Forest and Range Exp. Stn. Res. Pap. RM-72, 15 p. Fort Collins, Colo. Myers, C.A., C.B. Edminster, and F.G. Hawks- worth 1976. SWYLD2: Yield tables for even-aged and two-storied stands of southwestern ponderosa pine, including effects of dwarf mistletoe. USDA Forest Serv., Rocky Mountain Forest and Range Exp. Stn. Res. Pap. RM-163, 25 p. Fort Collins, Colo. Pierce, W.R. 1960. Dwarf mistletoe and its effect upon the larch and Douglas-fir of western Montana. Mont. State Univ. School of For. Bull. 10, 38 p. Missoula, Mont. Robins, J.K. 1972. Dwarf mistletoe aerial surveying method: results of preliminary trials in the Athabasca Forest, Alberta, March 1972. Can. Forest Serv., Northern Forest Res. Centre Misc. Rept. NOR-Y-10, 4 p. Calgary, Alberta, Can. Scharpf, R.F. 1977. Dwarf mistletoe does not increase trunk taper in released red firs in Cal- ifornia. USDA Forest Serv., Pacific South- west Forest and Range Exp. Stn. Res. Note PSW-326, 3 p. Berkeley, Calif. Shea, K.R. 1963. Marking guide evolved for mistletoe- hit Douglas-fir. For. Indus. 90:58-59. Shea, K.R. 1964. Diameter increment of ponderosa pine infected with dwarf mistletoe in south- central Oregon. J. For. 62:743, 746-748. Smith, R.B. 1969. Assessing dwarf mistletoe on western hemlock. For. Sci. 15:277-285. Smith, R.B., and E.F. Wass 1976. Field evaluation of ecological dif- ferentiation of dwarf mistletoe on shore pine and western hemlock. Can. J. For. Res. 6:225-228. Toko, H.V., and C.E. Carlson 1968. Dwarf mistletoe survey procedure. USDA Forest Serv., Northern Region Ins. and Dis. Rept . , 11 p. Missoula, Mont. Walters, J.W., and D.H. Brown 1973. An administrative study of sampling techniques in dwarf mistletoe-infested stands. USDA Forest Serv., Rocky Mountain Region Timber Manage. Rept., 11 p. Lakewood, Colo . Walters, J.W., and B.W. Geils 1977. Technical report - simulated yield tables for dwarf mistletoe management in pon- derosa pine stands (SWYLD2 program). Phase I - two storied stands, Chalender Ranger District, Kaibab National Forest, Arizona. USDA Forest Serv., Southwestern Region Rept. R-3 77-11, 25 p. Albuquerque, N.M. Weir, J.R. 1916. Larch mistletoe: some economic con- siderations of its injurious effects. U.S. Dep. Agric. Bull.317, 25 p.