Role of Repellents and Deterrents in Feeding of Scolytus

15 Role of Repellents and Deterrents in Feeding of Scolytus

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on May 30, 2013 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0062.ch015

Multistriatus D A L E M . NORRIS 642

Russell Laboratories, University of Wisconsin, Madison, W I 53706

Bark beetles i n the genus: Scolytus (Family: Scolytidae) not only "attack" suitable host trees for production and maturation of progeny, but also feed facultatively (i.e., such feeding i s not obligatory) i n the twigs of vigorously healthy hosts. Findings reported in this paper relate especially to phytochemicals (allomones) i n non-host trees which repel the species, Scolytus multistriatus, from alighting on such healthy plants and/or deter feeding on their tissues. Such repellent and deterrent chemicals of non-host species of trees combined with attractants, arrestant and feeding-stimulant chemicals of healthy hosts (especially Ulmus spp., family: Ulmaceae) are major determinants of the beetle arrival at, and acceptance of, host elm twigs for feeding (1). Though the complete complement of allomonic allelochemicals in species of plants may be complex and variable among individuals and plant parts (2), our study of certain allomones against S. multistriatus i n ten genera of trees i n nine families of dicotyledonous angiosperms revealed apparently similar structural and/or electrochemical molecular characteristics among the identified chemicals. I t i s intriguing and perhaps significant that most of these plant defense chemicals would seem capable of interacting with the lipoprotein neural membrane receptors for the potent allomone, juglone (5-hydroxy-1,4-naphthoquinone, Figure 1), which have been isolated and partially characterized from antennae of S. multistriatus and Periplaneta americana (3-10). Because of the hundreds of allomonic chemicals of non-host plants which an insect species may encounter, a specific receptor macromolecule for each chemical messenger obviously i s genetically untenable. This now obvious situation thus encourages hypotheses of mechanisms for sensory neural receptor-chemical messenger interactions which allow numerous messenger ligands to interact with a given receptor macromolecule i n a "quantal" manner. We (11) proposed such an unifying working hypothesis based on our early experimentation with the "juglone-type" receptor and on much supportive data from other areas of receptor neurobiology. Our continued experimental testing of this hypothesis has yielded

215 In Host Plant Resistance to Pests; Hedin, P.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Host Plant Resistance to Pests; Hedin, P.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Figure 1. Molecular structures of studied allomones from non-host tree species and kairomones from host Ulmus americana for Scolytus multistriatus


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encouraging data. The manners i n which the allomones reported i n t h i s paper seem t o support the hypothesis w i l l be discussed.


Table I. Non-Host Trees* Examined For Allomones Against Scolytus m u l t i s t r i a t u s Feeding Botanical Family

Genus

Species

Common Name

Aceraceae

Acer

negundo saccharinum

Boxelder S i l v e r maple

Hippocastanaceae

Aescuius

octandra

Yellow buckeye

Juglandaceae

Carya

cordiformis ovata

Bitternut hickory Shagbark h i c k o r y

Juglans

nigra

Black walnut

Oleaceae

Fraxinus

americana

White ash

Magnoliaceae

Magnolia

Cucumber t r e e acuminata (typical) var. acuminata

Rosaceae

Ma lus

pumila

Apple

Salicaceae

Populus

deltoïdes

Eastern cottonwood

Fagaceae

Quereus

macrocarpa alba

Bur oak White oak

Leguminosae

Robinia

pseudoacacia

Black

*Taxonomy taken from

locust

(12).

Methods Of Phytochemical

Analyses

Procedures used i n our i n i t i a l e x t r a c t i o n , p u r i f i c a t i o n and i d e n t i f i c a t i o n o f chemicals from t i s s u e o f non-hosts (Table I) and hosts ( i . e . , Ulmus), and t h e i r bioassay with i n s e c t s p e c i e s , have been d e t a i l e d (13-18). More recent i n v e s t i g a t i o n a l s o employed chemical methods d e t a i l e d , o r c i t e d , by Harborne (19). Our recent bioassay methods remained the same as i n e a r l i e r s t u d i e s . A schematic view o f the p e t r i - d i s h assay chamber used i n our bark b e e t l e bioassays termed "Assay #1" and "Assay #2" i s shown i n F i g u r e 2. Assay #1 was a simple feeding-choice t e s t between two uniform d i s c s of e l d e r b e r r y stem p i t h (presented on the " f l o o r " of the chamber); one d i s c u s u a l l y had been soaked i n the s o l v e n t and the other i n s o l v e n t p l u s candidate chemical o r f r a c t i o n o f crude e x t r a c t from a p l a n t t i s s u e . Assay #2 evaluated the v o l a t i l e p r o p e r t i e s o f candidate e x t r a c t s , f r a c t i o n s o r pure chemicals. Such a treatment was a p p l i e d t o one o f two p i t h d i s c s p o s i t i o n e d on the l i d of the p e t r i d i s h (Figure 2) such t h a t one was l o c a t e d d i r e c t l y above each o f the two p i t h d i s c s on the f l o o r o f the chamber as used i n Assay #1. The other d i s c on the


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H O S T P L A N T RESISTANCE T O

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l i d was t r e a t e d with s o l v e n t . In Assay #2, both lower d i s c s were uniformly t r e a t e d with 0.1 M sucrose, which i s a feeding stimu l a n t f o r our t e s t bark b e e t l e s . The d i f f e r e n c e i n b e e t l e feeding on the lower d i s c under the t r e a t e d upper d i s c versus on the one under the upper s o l v e n t - t r e a t e d d i s c was measured.


E f f e c t s Of E x t r a c t s Of Non-Host Carva And S.. m u l t i s t r i a t u s Feeding

Juglans Trees On

Our i n i t i a l s t u d i e s focused on species of Carya (Table I ) , and t h e i r chemical c o n s t i t u e n t s which prevent multistriatus alightment on, and feeding i n , t i s s u e s of h i c k o r i e s (14, 15). The aglycone, juglone (5-hydroxy-l,4-naphthoquinone, Figure 1), was shown to keep £3. m u l t i s t r i a t u s o f f Carya c o r d i f o r m i s and Carya ovata (Figure 3, Table I I ) . This allomone occurs mostly as a-hydrojuglone-4-3-D-glucoside i n i n t a c t healthy c e l l s i n Carya. However, some f r e e naphthoquinone i s p e r c e p t i b l e even by human o l f a c t i o n i n the atmosphere surrounding vigorous h i c k o r i e s . I f c e l l s are ruptured, the p l a n t becomes p h y s i o l o g i c a l l y s t r e s s e d as during drought, or the p l a n t experiences a m i c r o b i a l l y caused disease, a d d i t i o n a l amounts of juglone are r e l e a s e d i n t o the atmosphere. I t would seem t h a t such a d d i t i o n a l releases of t h i s potent a l l o mone during i n i t i a l predator or p a r a s i t e attack, or other environmentally induced adverse c o n d i t i o n s may exemplify the dynamic nature of a p l a n t s p e c i e s allomonic chemistry. Our f i e l d observ a t i o n s and experiments have shown t h a t once a Carya t r e e becomes i r r e v e r s i b l y diseased, i t no longer can release juglone f o r defense. At t h i s p o i n t , secondary predators and p a r a s i t e s which a t t a c k dying t r e e s of s e v e r a l species appear on the p l a n t . It would seem that such secondary herbivores are not confronted by s i g n i f i c a n t amounts of the allomones which d e f e n s i v e l y serve healthy species of p l a n t s , Carya spp. i n t h i s p a r t i c u l a r example. More recent s t u d i e s of the type described f o r the Carya spp. have been conducted on Juglans n i g r a , black walnut (Table I ) , another r e p r e s e n t a t i v e of the f a m i l y : Juglandaceae. Juglone i n Juglans n i g r a a l s o proved t o be the major allomone against S. m u l t i s t r i a t u s feeding. 1

Molecular P r o p e r t i e s P o s i t i v e l y C o r r e l a t e d With Allomonic A c t i v i t y Of 1,4-Naphthoquinones. To i n v e s t i g a t e the molecular p r o p e r t i e s of 1,4-naphthoquinones i n v o l v e d i n making them a l l o monic against S_. m u l t i s t r i a t u s , the order of r e l a t i v e deterrency and i n h i b i t i o n of feeding of 2,3-dichloro-; 2-methyl-; 2-hydroxy-; 5-hydroxy-; 5,8-dihydroxy-; and the unsubstituted 1,4-naphthoquinone was determined. Results i n d i c a t e d t h a t the allomonic a c t i v i t y of 5-hydroxy1- > 5,8-dihydroxy- > unsubstituted 1,4- > 2hydroxy- > 2-methyl- > 2,3-dichloro-. With the s o l e exception of 2,3-dichloro-1,4-naphthoquinone, t h i s order of r e l a t i v e allomonic a c t i o n of the t e s t e d 1,4-naphthoquinones c o r r e l a t e d p o s i t i v e l y with the order of t h e i r r e l a t i v e combined redox p o t e n t i a l and



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Figure 2. Photograph of top and bottom of petri dish chamber used to bioassay extracts and pure chemicals for effects on Scolytus multistriatus feeding. Assay No. 1 used only two pith discs on floor of chamber. Assay No. 2 involved four discs: two on the floor (L ) and two on the lid (\J ). d

d

Figure 3. Inhibition of Scolytus multistriatus feeding on pith discs treated with Ulmus americana extract by addition of 2 X 10~ M luglone. (A) Feeding on Ulmus extract; (B) inhibition of feeding by adding Juglone. Solvent-treated control discs are in lower row of "A" and "B." 3


HOST P L A N T RESISTANCE T O PESTS

220

Table I I . Mean Feeding (Mm ) By 25 Scolytus m u l t i s t r i a t u s In 48 Hours on P i t h Discs Treated With A Standard Ulmus americana Bark E x t r a c t , F r a c t i o n s * Of Carya ovata Twig Bark E x t r a c t , Commercial Juglone Or Combinations

Treatment T.L.C , Band (R 0 ,60-0.80) Of C. ovata E x t r a c t (=Juglone) + Ulmus E x t r a c t

Feeding (Mm ) Treated** Control

Rating


f

Band R 0.60-0.80 Of £. ovata E x t r a c t Was Highly I n h i b i t o r y

0.8

f

Ulmus E x t r a c t

44.5

Highly

T.L.C. Bands (R 0.0-0.60, 0.80-1.00) Of £. ovata E x t r a c t + Ulmus E x t r a c t

40.2

Distillate (=Juglone) Of C. ovata E x t r a c t + Ulmus E x t r a c t

0.2

bG

0

Bands (R 0.0-0.60, 0.80-1.00) Of C. ovata E x t r a c t Were Non-inhibitory

ad

0

D i s t i l l a t e Of C. ovata E x t r a c t Was Highly I n h i b i t o r y

0.4

Highly

0.0

£. ovata Residue Was Highly Stimulatory

0.0

Juglone was Highly I n h i b i t o r y

0.0

Juglone Was Highly I n h i b i t o r y

Ulmus E x t r a c t

39.2

Residue A f t e r D i s t i l l a t i o n Of £. ovata E x t r a c t

34.8

-3 Juglone (2 χ 10 M) Re-Crystallized From T.L.C. Band R 0.60-0.80 + Ulmus E x t r a c t

0.3

Commercial Juglone (2 χ 10 M) + Ulmus E x t r a c t

0.4

Stimulatory

b C e

ef

adg

adgh

Stimulatory

•Methods p r e v i o u s l y d e t a i l e d by G i l b e r t et_ a_l. (14, 15) . **Values not followed by the same s u p e r s c r i p t l e t t e r s are s i g n i f i c a n t l y d i f f e r e n t at Ρ < 0.01 p r o b a b i l i t y .



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hydrogen-bonding c a p a b i l i t i e s . Hydroxyl s u b s t i t u t i o n ( s ) , with the i n t r a - and i n t e r - m o l e c u l a r hydrogen-bonding c a p a b i l i t i e s which they b r i n g t o the 1,4-naphthoquinone molécule, u n f a i l i n g l y made the naphthoquinone more r e p e l l e n t , or i n h i b i t o r y to feeding, than the r e l a t i v e redox p o t e n t i a l p r e d i c t e d . Two examples are (1) 2methyl- has a s l i g h t l y h i g h e r ( i . e . , more negative) redox potent i a l than 2-hydroxy-, but 2-hydroxy- proved more r e p e l l e n t and i n h i b i t o r y ; and (2) the unsubstituted 1,4- has a h i g h e r redox p o t e n t i a l than e i t h e r 5,8-dihydroxy- or 5-hydroxy-, but both of the l a t t e r chemicals were more r e p e l l e n t and i n h i b i t o r y t o S_. m u l t i s t r i a t u s . The 2,3-dichloro-1,4-naphthoquinone showed the l e a s t r e p e l l e n c y and i n h i b i t i o n of feeding even though i t has a higher redox p o t e n t i a l than the unsubstituted 1,4-naphthoquinone. Our t o t a l s t u d i e s suggest t h a t t h i s weak r e p e l l e n c y and i n h i b i t i o n to S_. m u l t i s t r i a t u s are probably a t t r i b u t a b l e t o the redox potent i a l of the naphthoquinone being so high t h a t only l i m i t e d revers i b l e energy exchange between the messenger and receptor could occur. T h i s i n t e r p r e t a t i o n gains f u r t h e r support from the e x p e r i mentally determined f a c t that 2,3-dichloro-1,4-naphthoquinone i s not s i g n i f i c a n t l y (P < 0.05) r e p e l l e n t or i n h i b i t o r y t o P e r i p l a neta americana. A l l of the other above-mentioned naphthoquinones not only are a l s o r e p e l l e n t and i n h i b i t o r y t o t h i s very d i f f e r e n t i n s e c t P_. americana, but the order of t h e i r r e l a t i v e allomonic a c t i v i t y i s the same as against iS. m u l t i s t r i a t u s . Thus i t would appear t h a t quinones which are allomonic to p a r t i c u l a r species of i n s e c t s , or other organisms, must have a redox p o t e n t i a l ( i . e . , energy-sharing o r -exchanging c a p a b i l i t y ) w i t h i n a f i n i t e range. Such s p e c i e s - c h a r a c t e r i s t i c l i m i t s on the redox range w i t h i n which i t s chemical sensing system may exchange i n f o r m a t i o n a l energy with i t s environment may serve a major r o l e i n the chemical e c o l o g i c a l o r d e r i n g of species d i s t r i b u t i o n s and d e n s i t i e s . Our s t u d i e s (14, 15, 20) comparing the b e h a v i o r a l e f f e c t s of juglone on S_. m u l t i s t r i a t u s , f o r which Carya spp. are non-hosts; and on the close b e e t l e r e l a t i v e Scolytus quadrispinosus, f o r which Carya are major hosts, o f f e r encouraging f u r t h e r evidence that such s p e c i e s c h a r a c t e r i s t i c l i m i t s on the redox range of chemical sensing systems operate i n h e l p i n g t o determine i n s e c t - h o s t p l a n t i n t e r a c t i o n s . S. quadrispinosus feeds r e a d i l y on amounts of the potent allomone, juglone, which k i l l m u l t i s t r i a t u s . D i f f e r i n g capab i l i t i e s f o r d e t o x i f y i n g juglone probably e x i s t i n these two Scolytus s p e c i e s , but the primary chemical sensing systems must d i f f e r electrochemically. E l e c t r o c h e m i c a l D i f f e r e n c e Between An Allomone And A Kairomone For Scolytus m u l t i s t r i a t u s . In conjunction with the aforementioned experimental e v a l u a t i o n s of various 1,4-naphthoquinone s as allomones against S_. m u l t i s t r i a t u s , the simple q u i none, p-benzoquinone (Figure 1), a l s o was bioassayed. In the same study the c l a s s i c a l redox couple of p-benzoquinone, ρ-hydroquinone (Figure 1) ( i . e . , 1,4-dihydroxybenzene), was evaluated. These


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H O S T P L A N T RESISTANCE T O PESTS

combined s t u d i e s (JL, 21, 22) showed t h a t ρ-hydroquinone i s a s i g n i f i c a n t kairomone ( i . e . , feeding stimulant) f o r S_. m u l t i s t r i atus, and p-benzoquinone i s an allomone. Thus, i n t h i s i n s e c t the e l e c t r o c h e m i c a l d i f f e r e n c e between an allomone and a kairomone i s the d i f f e r e n c e between accepting or donating (or v a r i o u s l y shar ing) one o r two e l e c t r o n s and protons (Figure 1 ) .


Flavonoids As Allomones And Kairomones To Scolytus m u l t i s t r i a t u s Feeding The compound (+)-catechin-5-3-D-xylopyranoside was reported (24) as a feeding stimulant i n Ulmus f o r S_. m u l t i s t r i a t u s . Our s t u d i e s (25) o f phytochemical stimulants o f S_. m u l t i s t r i a t u s feed i n g i n d i c a t e d that the f l a v o n o i d aglycone, (+)-catechin (Figure 1), from Ulmus americana a l s o promoted feeding. Such a f l a v a n - 3 o l i n v o l v e s the most h i g h l y reduced C u n i t ( i . e . , propane u n i t ) found i n f l a v o n o i d s (23, 26). The d i f f e r e n t l e v e l s o f o x i d a t i o n among the types o f f l a v o n o i d s are expressed i n the unit that j o i n s the "A" and "B" r i n g s . Thus, the f l a v a n - 3 - o l s (catechins) and dihydrochalcones are the most reduced, and the f l a v o n o l s are the most o x i d i z e d (Table I I I ) . Table I I I . Oxidation S t a t e s * In The C Of F l a v o n i d s

Units Of D i f f e r e n t Types

F l a v o n i d Name

Structure o f

Flavan-3-ols

A-CH -CHOH-CHOH-B

Hydrochalcones

A-CO-CH -CH -B

Chalcones

A-CO-CH=CH-B

Flavanones

A-CO-CH -CHOH-B

Unit

2

2

2

2

Leucoanthocyanidins

A-CHOH-CHOH-CHOH-B

Flavones

A-CO-CH -CO-B

Anthocyanidins

A-CH -CO-CO-B

Benzalcoumaranones

A-CO-CO-CH -B

Flavanonols

A-CO-CHOH-CHOH-B

Flavonols

A-CO-CO-CHOH-B

2

*Taken from Geissman

2

2

(23).

In a l l the s t r u c t u r e s i n Table I I I , the A r i n g i s assumed t o c a r r y an o-hydroxyl group which engages i n r i n g closure t o form the chromanol, chromanone, e t c . , r i n g . E n o l i z a t i o n , l o s s o f the elements o f water o r f l a v y l i u m s a l t formation are processes t h a t do not a f f e c t o x i d a t i o n l e v e l . Thus, f l a v o n e s , anthocyani-


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dins and benzalcoumaranones, o f q u i t e d i f f e r e n t s t r u c t u r e s , a l l possess the equivalent of two -CO- and one "CH^- groups. Based on data presented i n Table IV, the r e l a t i v e l y reduced, non-carbonyl-bearing f l a v a l - 3 - o l , (+)-catechin, s i g n i f i c a n t l y stimulated m u l t i s t r i a t u s feeding. When mixed with a standard amount (5 mg/ml) o f benzene e x t r a c t a b l e s from U. americana twig bark and phloem, c a t e c h i n had an a d d i t i v e e f f e c t on b e e t l e feedi n g . Moving t o two non-host-derived dihydrochalcones, p h l o r e t i n from Malus pumila and 2 ,6 -dihydroxy-4'-methoxy dihydrochalcone from Populus deltoïdes, n e i t h e r stimulated a s i g n i f i c a n t (P < 0.05) amount o f feeding. Upon a d d i t i o n t o the Ulmus e x t r a c t , each compound s i g n i f i c a n t l y (P < 0.01) reduced the amount o f feeding (Table I V ) . Thus, thèse two r e l a t i v e l y reduced f l a v o n o i d s , but each with a carbonyl group, c l e a r l y i n h i b i t e d feeding on Ulmus e x t r a c t ; whereas, the comparably reduced (+)-catechin, without the carbonyl, stimulated feeding. These d i f f e r e n c e s i n e f f e c t s o f comparably reduced f l a v o n o i d s , f l a v a l - 3 - o l s and hydrochalcones, may be explained by (1) d i f f e r e n c e s i n the d i s t r i b u t i o n s o f charge i n the r e s p e c t i v e molecules and/or (2) an unique f u n c t i o n a l group ( i . e . , carbonyl) on the C (propane) p o r t i o n of the molecules. Swain (27) commented that the carbonyl group i n f l a v o n o i d s does not show the general r e a c t i o n s o f such groups with keto reagents, except Grignard reagents. However, these Grignard r e a c t i o n prop e r t i e s perhaps make them comparable t o the p r e v i o u s l y discussed simple quinone, p-benzoquinone; and c e r t a i n 1,4-naphthoquinones which are i n h i b i t o r y t o S_. m u l t i s t r i a t u s feeding. The carbonyl a t C^ o f the propane p o r t i o n o f these f l a v o n o i d s i s s i t u a t e d as an a , 3-unsaturated ketone with regard t o r i n g A o f the f l a v o n o i d molec u l e . T h i s apparently i s the primary common chemical s t r u c t u r a l c h a r a c t e r i s t i c which makes these f l a v o n o i d s and the discussed quinones deterrents and i n h i b i t o r s o f S_. m u l t i s t r i a t u s . The hydroxyl s i t u a t e d a t C on the A r i n g a l s o i s s u f f i c i e n t l y c l o s e to the C^ carbonyl t o allow i n t r a m o l e c u l a r hydrogen bonding between the hydrogen o f the hydroxyl and the C^ carbonyl. Our s t u d i e s o f the e f f e c t s of various s u b s t i t u e n t groups on the a l l o monic a c t i v i t y o f 1,4-naphthoquinones have c l e a r l y shown that such adjacent hydroxyIs enhance the a c t i v i t y o f such quinones. Thus, there would seem t o be t h i s important hydroxyl s i t u a t i o n i n c e r t a i n allomonic naphthoquinones and f l a v o n o i d s . 1


in

,

3

5

I f we next consider two f l a v o n o i d s , kaempferol as i s o l a t e d from Robinia pseudoacacia and q u e r c e t i n as i s o l a t e d from Quercus macrocarpa, which are among the most h i g h l y o x i d i z e d f l a v o n o l s (Figure 1, Table IV) , they showed l e v e l s o f i n h i b i t i o n o f S^. m u l t i s t r i a t u s feeding, when mixed with the Ulmus e x t r a c t , which were s i g n i f i c a n t l y (P < 0.05 o r 0.01) greater than those caused by the two t e s t e d hydrochalcones. The a d d i t i o n a l l e v e l s o f o x i d a t i o n i n the f l a v o n o l s p l u s the apparently important carbonyl and adjacent hydroxyls probably e x p l a i n t h e i r g r e a t e r allomonic e f f e c t s under these t e s t c o n d i t i o n s .



224

Table IV. Mean Feeding (Mm ) By 25 Scolytus m u l t i s t r i a t u s Adults In 48 Hours On P i t h D i s c s Treated With A Standard E x t r a c t Of Ulmus americana Twig Bark, A Known F l a v o n i d Or Combination Of Both Molar Concentration


Flavonid (+)-Catechin

2 X 10"

(+)-Catechin + Ulmus E x t r a c t

2 X 10"

3

3

—

Ulmus E x t r a c t

2 X 10"

Phloretin + Ulmus E x t r a c t

2 X 10" J

1

,

—

Ulmus americana

24. 3

a

0.0

Ulmus americana

52.4

b

0.0

39.3°

0.0

d

Ma l u s pumila

4.3

Malus pumila

22.6

—

36.4

0.0

0.0 0.0

Cf

I

2 ,6 -Dihydroxy-4 -methoxy dihydrochalcone 1

Feeding (Mm ) Treated* Solvent

— 3

Phloretin

Ulmus E x t r a c t

Plant Source

2 X 10"

3

Populus deltoïdes

0.0

d

3.1 *

1

2 ,6 -Dihydroxy-4' -methoxy dihydrochalcone + Ulmus Extract Ulmus E x t r a c t

2 X 10" J

—

Kaempferol

2 X 10"

Kaempferol + Ulmus E x t r a c t

2 X 10~

Populus deltoïdes

— 3

3

a e h

0.0

34.8

C f ±

0.0

Robinia pseudoacacia

o.o

Robinia pseudoacacia

14. 3

Ulmus E x t r a c t

gj

0.0

k

0.0

37.6 3

Quercetin

2 X 10"

Quercetin + Ulmus E x t r a c t

•3 2 X 10"

Ulmus E x t r a c t

20.6

—

C f i l

Quereus macrocarpa

o.o

Quereus macrocarpa

16.1^ 35.7

C f i l

0.0 0.0

g j m

0.8 °

0.0

*Values not bearing the same s u p e r s c r i p t l e t t e r are s i g n i f i c a n t l y d i f f e r e n t from each other (P < 0.05).


15.

NORRis

Repellents

and Deterrents

E f f e c t s Of C e r t a i n Coumarins And P h e n o l i c s t r i a t u s Feeding C

Acids

On S_. m u l t i

C

Compounds c o n t a i n i n g t h e ^ ~ 3 p h e n y l p r o p a n e u n i t a r e a b u n dant i n phytochemistry. Coumarins a r e phenylpropanoid i n origin, a n d a r e f o r m e d b y r i n g c l o s u r e o f a g ~ 3 compound s u c h a s ohydroxy cinnamic a c i d . The c o u m a r i n , a e s c u l e t i n , from t h e n o n h o s t A e s c u l u s o c t a n d r a p r o v e d t o b e a p o t e n t a n t i f e e d a n t f o r S_. m u l t i s t r i a t u s ( F i g u r e 1, T a b l e V ) . F r a x e t i n , a coumarin i s o l a t e d from the non-host Fraxinus americana, a l s o y i e l d e d s i g n i f i c a n t a n t i f e e d a n t e f f e c t s on m u l t i s t r i a t u s ( F i g u r e 1, T a b l e V ) . I t i s i n t e r e s t i n g and apparently c h e m i c a l l y s i g n i f i c a n t t h a t t h e p h e n o l i c a c i d s o-hydroxy- and ρ-hydroxy- c i n n a m i c a c i d a l s o were v e r y i n h i b i t o r y t o S_. m u l t i s t r i a t u s f e e d i n g ( T a b l e V) . Because t r a n s - c i n n a m i c a c i d ( T a b l e V) s i g n i f i c a n t l y s t i m u l a t e d S_. m u l t i s t r i a t u s f e e d i n g , t h e p r e s e n c e o f a h y d r o x y l on t h e b a s i c c i n n a m i c a c i d s t r u c t u r e c h a n g e d t h e e f f e c t s o f t h e m o l e c u l e on b e e t l e f e e d i n g from s t i m u l a t o r y t o i n h i b i t o r y . T h u s , among t h e t e s t e d c o u m a r i n s a n d c i n n a m i c a c i d s , t h e h y d r o x y l a n d i t s e f f e c t on t h e o v e r a l l c h a r g e d i s t r i b u t i o n i n t h e m o l e c u l e may d e t e r m i n e f e e d i n g a c t i v i t y with t h i s s p e c i f i c insect. C


225

in Feeding

C

In view o f o u r p r e v i o u s l y p r e s e n t e d evidence t h a t t h e e f f e c t s o f v a r i o u s f l a v o n o i d s upon S_. m u l t i s t r i a t u s f e e d i n g c o r r e l a t e w i t h (1) t h e r e l a t i v e d e g r e e o f o x i d a t i o n , e s p e c i a l l y i n t h e C , p r o p a n e , u n i t ; a n d (2) t h e p r e s e n c e o r a b s e n c e o f p a r t i c u l a r l y a c a r b o n y l a n d / o r one o r more h y d r o x y l s , common f u n c t i o n a l g r o u p a n d e l e c t r o c h e m i c a l p r o p e r t i e s s e e m i n g l y e x i s t among t h e s e s t u d i e d a l l o m o n i c chemicals i n c l u d i n g t h e simple quinone, p-benzoquinone, and t h e 1,4-naphthoquinones. B a s e d on o u r b e s t u n d e r s t a n d i n g o f t h e f u n c t i o n a l group a n d e l e c t r o c h e m i c a l p r o p e r t i e s o f t h e c h e m o s e n s o r y n e u r a l membrane receptor i n m u l t i s t r i a t u s a n d P e r i p l a n e t a a m e r i c a n a (_5, 1JL) f o r 1,4-naphthoquinones, t h i s r e c e p t o r mechanism s h o u l d o p e r a t e i n v i v o and i n v i t r o with the other allomonic chemicals discussed thus f a r i n t h i s chapter. To i l l u s t r a t e f u r t h e r t h e a p p a r e n t i m p o r t a n c e o f u n s a t u r a t i o n i n a carbon s i d e c h a i n and o f t h e charge d i s t r i b u t i o n i n p h e n o l i c s f o r d e t e r m i n i n g w h e t h e r a m o l e c u l e s t i m u l a t e s o r i n h i b i t s IS. multistriatus feeding, i t i s s i g n i f i c a n t that protocatechuic acid ( T a b l e V) was s t i m u l a t o r y . P r e v i o u s l y p u b l i s h e d d a t a (_1, 18, 22) a l s o showed t h a t s e v e r a l p h e n o l i c s s i m i l a r t o p r o t o c a t e c h u i c a c i d (e.g., p r o c a t e c h u i c aldehyde, v a n i l l i n , s y r i n g a l d e h y d e and ph y d r o x y b e n z a l d e h y d e ) s t i m u l a t e S_. m u l t i s t r i a t u s f e e d i n g . Likewise the C l i g n a n , α c o n i d e n d r i n , f r o m Ulmus s t i m u l a t e d f e e d i n g . I t i s a a i m e r o f C^-C^ u n i t s w i t h a l o w e r d e g r e e o f u n s a t u r a t i o n i n t h e C^, p r o p a n e , p o r t i o n s t h a n i s p r e s e n t i n t h a t u n i t o f t h e i n h i b i t o r y ρ-hydroxycinnamic a c i d .


H O S T P L A N T RESISTANCE T O PESTS

226

Table V. Mean Feeding (Mm ) By 25 Scolytus m u l t i s t r i a t u s Adults In 48 Hours On P i t h Discs Treated With A Standard E x t r a c t Of Ulmus americana Twig Bark, A Coumarin, A Phenolic A c i d , A Lignan Or Com binations Molar Concentration


Chemical Aesculetin

2

X

10"

Aesculetin + Ulmus E x t r a c t

2

X

10"

Ulmus E x t r a c t

3

o.o

Aesculus octandra

12.6

-a

2

X

10"

Fraxetin + Ulmus E x t r a c t

2

X

10"

Ulmus E x t r a c t

3

b

0.0

34.9°

0.0

Fraxinus americana

4.i

0.0

Fraxinus americana

19.3

—

—

o-Hydroxy cinnamic a c i d

2

X

10~

o-Hydroxy cinnamic a c i d + Ulmus E x t r a c t

2

X

10" J

Ulmus E x t r a c t

3

3

X

10~

2

X

10" J

36.0°

Commercial

10.3

—

0.0

Θ

o.o

Q

2

a d

Commercial

—

ρ-Hydroxy cinnamic a c i d

(Mm ) Solvent

0.0

a

•u

—

3

Feeding Treated*

Aesculus octandra

—

Fraxetin

ρ-Hydroxy cinnamic a c i d Ulmus E x t r a c t

Plant Source

f

0.0

a d g

0.0

bh

0.0

C f l

0.0

a d g j

0.0

38.1

Commercial

o.o

Commercial

14.8

+

Ulmus E x t r a c t

—

—

trans-cinnamic acid

2

X

io~

Protocatechuic acid

2

X

10"

2

X

α-Conidendrin* *

10"

3 3 3

bk

35.2

Commercial

24.8

Commerical

27.i

Ulmus

16.8

e f ± 1

0.0 0.4

em

0.6

m p

0.9

e k n q

0.3

•Values not followed by the same s u p e r s c r i p t l e t t e r are s i g n i f i c a n t l y d i f f e r e n t (P < 0.05). **A l i g n a n , a dimer o f C -C

units.


15.

NORRis

Repellents

and

Deterrents

in

227

Feeding


A l k a l o i d s In Non-Host Species As Allomones For Scolytus striatus

muJLti-

About 15-20% of a l l v a s c u l a r p l a n t s contain a l k a l o i d s (28). Our primary d e f i n i t i o n of an a l k a l o i d i s a b a s i c , nitrogen-con t a i n i n g compound. Further d e s c r i p t i v e c h a r a c t e r i s t i c s which we a s c r i b e to " a l k a l o i d s " are (1) by-products of p r o t e i n metabolism which are (2) methylated on e i t h e r n i t r o g e n or, when present, on hydroxyl groups and so removed from general metabolism. They are more or l e s s t o x i c substances which act p r i m a r i l y on the nervous system. These p h y s i o l o g i c a l p r o p e r t i e s make them prime candidates as allomones against i n s e c t s such as S_. m u l t i s t r i a t u s . Our s t u d i e s of major allomones i n non-host Acer negundo, Acer saccharinum and Magnolia acuminata var. acuminata against S_. m u l t i s t r i a t u s feeding revealed two types of a l k a l o i d a l deterrents and a n t i f e e d a n t s , the i n d o l e substance gramine (Figure 1, Table V I ) , from the Acer spp; and the b e n z l i s o q u i n o l i n e d e r i v a t i v e s , such as magnoline (Figure 1), from the Magnolia sp. (Table V I ) . I t i s b e l i e v e d t h a t the q u i n o l i n e a l k a l o i d s are formed from i n d o l e p r e c u r s o r s (29). 2 Table VI. Mean Feeding (Mm ) By 25 Scolytus m u l t i s t r i a t u s Adults In 48 Hours On P i t h Discs Treated With A Standard E x t r a c t Of Ulmus americana, A Known A l k a l o i d Or Combination Of Both Molar Concentration

Alkaloid Gramine

2 X ίο"

Gramine + Ulmus E x t r a c t

2 X 10

Ulmus E x t r a c t

Acer

negundo

0. o

3

Acer

negundo

21. 4

—

—

Magnoline

2 X ίο"

Magnoline + Ulmus E x t r a c t

2 X ίο"

3

—

Feeding (Mm ) Treated* Control

3

3

Ulmus E x t r a c t

Source P l a n t Genus Species

0.0

b

0.0 0.0

39. 8° a d

0.4

30. 4

e

0.0

38. 6

C f

0.0

Magnolia acuminata var. acuminata

5. 2

Magnolia acuminata var. acuminata —

a

*Values not followed by the same s u p e r s c r i p t l e t t e r are c a n t l y d i f f e r e n t (P < 0.05 or 0.01).

signifi

Our l i m i t e d s t u d i e s of a l k a l o i d s as i n h i b i t o r s of feeding by _S. m u l t i s t r i a t u s do not allow s i g n i f i c a n t s p e c u l a t i o n or a hypo t h e s i s about t h e i r s t r u c t u r a l chemical p r o p e r t i e s r e s p o n s i b l e f o r the observed i n h i b i t i o n of £. m u l t i s t r i a t u s feeding; however, Horowitz (30) d i d r e p o r t the i n t e r e s t i n g observation that forming the n i t r o g e n oxime d e r i v a t i v e ( i . e . , =N-0H) of the carbonyl group


HOST P L A N T RESISTANCE T O

228

PESTS

i n aglycones of c e r t a i n f l a v o n o i d s d i d not a b o l i s h the b i t t e r t a s t e of these compounds. Thus, some i n h i b i t o r y a l k a l o i d s , f l a v o noids, coumarins, naphthoquinones and simple p-benzoquinones may have r a t h e r s i m i l a r s t r u c t u r a l chemical c h a r a c t e r i s t i c s which are c o n t r i b u t o r y t o t h e i r feeding deterrency and i n h i b i t i o n against £. multistriatus.


General D i s c u s s i o n Our reported research f i n d i n g s on some apparent common molec u l a r c h a r a c t e r i s t i c s found among a r a t h e r d i v e r s e group of phytochemicals which r e p e l and/or i n h i b i t feeding by S_. m u l t i s t r i a t u s suggest that they a l l may i n t e r a c t with our demonstrated "quinone" receptor i n the chemosensory primary neurons i n the i n s e c t . This view seems to be supported s i g n i f i c a n t l y by the f i n d i n g s of Horow i t z (30). Horowitz (30) d i s c u s s e d the r o l e s of f r e e d i s a c c h a r i d e s , aglycones and the corresponding g l y c o s i d e s i n the e l i c i t a t i o n of t a s t e sensations i n humans. His evidence i n d i c a t e d t h a t the d i s s a c h a r i d e s , neohesperidose or r u t i n o s e , need to be attached to an aglycone to e l i c i t intense t a s t e . The next c o n s i d e r a t i o n , i n view of our r e s u l t s reported from assays with S_. m u l t i s t r i a t u s , i s the r o l e ( s ) of the aglycone. Regarding the s t r u c t u r e of the aglycone, the carbonyl and i t s a s s o c i a t i o n with a,3-unsaturation and an adjacent hydroxyl seemed s t r o n g l y c o r r e l a t e d with s i g n i f i c a n t i n h i b i t i o n of S_. m u l t i s t r i a t u s feeding. P h l o r e t i n , which has the carbonyl and an adjacent hydroxyl, was the l e a s t i n h i b i t o r y of t e s t e d f l a v o n o i d s . Adding a,3-unsaturation u n f a i l i n g l y increased the e f f e c t s on g u s t a t i o n . Removal of the carbonyl (e.g., catechin) r e s u l t e d i n s i g n i f i c a n t s t i m u l a t i o n r a t h e r than i n h i b i t i o n of i n s e c t feeding. Horowitz (30) concluded that there was s c a r c e l y any information regarding the r o l e of the carbonyl group of f l a v o n o i d s i n e l i c i t i n g the t a s t e response i n humans. However, he reported t h a t removal of the carbonyl from the a g l y cone ( i . e . , reducing i t to hydroxyl) seemed t o cause the t a s t e of b i t t e r n e s s to disappear. These p r e v i o u s l y reported f i n d i n g s with humans thus would seemingly agree w e l l with our demonstrated importance of the carbonyl group or a f u n c t i o n a l l y comparable nitrogenous group, with appropriate a s s o c i a t e d molecular unsaturation and hydroxyls, i n aglycones which promote r e p e l l e n c y o f , or feeding i n h i b i t i o n i n , S_. m u l t i s t r i a t u s . There seems to be an encouraging amount of evidence t h a t the "quinone" receptors demonstrated i n our s t u d i e d species of i n s e c t s i n t e r a c t as chemoreceptors with many, i f not most, of the other s t u d i e d allomones. Acknowledgments T h i s research was supported by the College of A g r i c u l t u r a l and L i f e Sciences, the Wisconsin Department of Natural Resources;


15.

NORRis

Repellents

and Deterrents

in

Feeding

229

and by research grants Nos. GB-6580, 8756, 41868 and BNS 74-00953 from the N a t i o n a l Science Foundation.


Literature

Cited

1. Norris, D.M., Baker, J.E., Borg, T.K., Ferkovich, S.M., Rozental, J.M., Contrib. Boyce Thompson Inst., (1970), 24, 263274. 2. Rice, E.L., "Allelopathy", p. 353, Academic Press, New York, 1974. 3. Norris, D.M., Ferkovich, S.M., Rozental, J.M., Baker, J.E., Borg, T.K., Science, (1970), 170, 754-755. 4. Ferkovich, S.M., Norris, D.M., Experientia, (1972), 28, 978979. 5. Rozental, J.M., Norris, D.M., Nature, (1973), 244, 370-371. 6. Rozental, J.M., Norris, D.M., Life Sciences, (1975), 17, 105110. 7. Singer, G., Rozental, J.M., Norris, D.M., (1975), Nature, 256, 222-223. 8. Norris, D.M., Bull. Entomol. Soc. Amer., (1976), 22. 27-30. 9. Norris, D.M., Symp. Biol. Hung., (1976), 16, 197-201. 10. Norris, D.M., Rozental, J.M., Samberg, G., Singer, G., Comp. Biochem. Physiol., (1977), in press. 11. Norris, D.M., Experientia, (1971), 27, 531-532. 12. Little, E.L., "Check List of Native and Naturalized Trees of the United States (Including Alaska)", Agric. Handbook, 41, p. 472, U.S. Govt. Printing Office, Washington, D.C., 1953. 13. Norris, D.M., Baker, J.E., J. Insect Physiol., (1967), 13, 955-962. 14. Gilbert, B.L., Baker, J.E., Norris, D.M., J. Insect Physiol., (1967), 13, 1453-1459. 15. Gilbert, B.L., Norris, D.M., J. Insect Physiol., (1968), 14, 1963-1068. 16. Baker, J.E., Norris, D.M., Ann. Entomol. Soc. Amer., (1968), 61, 1248-1255. 17. Baker, J.E., Norris, D.M., Ent. exp. appl., (1968), 11, 464469. 18. Meyer, H.J., Norris, D.M., J. Insect Physiol., (1974), 20, 2015-2021. 19. Harborne, J.B., "Phytochemical Methods", p. 278, Chapman and Hall, London, 1973. 20. Goeden, R.D., Norris, D.M., Ann. Entomol. Soc. Amer., (1964), 57, 743-749. 21. Norris, D.M., Nature, (1969), 222, 1263-1264. 22. Norris, D.M., Ann. Entomol. Soc. Amer., (1970), 63, 476-478. 23. Geissman, T.A., pp. 213-250, "Comprehensive Biochemistry", 9, Florkin, M. and Stotz, E.A., Eds., p. 265, Elsevier, Amsterdam, 1963. 24. Hoskotch, R.W., Chatterji, S.K., Peacock, J.W., Science, (1970), 167, 380-382.



230


25. Meyer, H.J., "Ph.D. Thesis", p. 246, University of Wisconsin, Madison, 1974. 26. Swain, T., "Chemical Plant Taxonomy", p. 543, Academic Press, London, 1963. 27. Swain, T., pp. 211-245, "Chemistry and Biochemistry of Plant Pigments", Goodwin, T.W., Eds., p. 583, Academic Press, London, 1965. 28. Hegnauer, R., pp. 389-427, "Chemical Plant Taxonomy", Swain, T., Ed., p. 543, Academic Press, London, 1965. 29. Relijk, J., Pharm. Weekbl., (1958), 93, 625. 30. Horowitz, R.M., pp. 545-571, "Biochemistry of Phenolic Compounds", Harborne, J.B., Ed., p. 618, Academic Press, London, 1964.


Role of Repellents and Deterrents in Feeding of Scolytus

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