CALIFORNIA STATE UNIVERSITY • FRESNO

SCHOOL OF AGRICULTURAL SCIENCES AND TECHNOLOGY ^CALIFORNIA AGRICULTURAL TECHNOLOGY INSTITUTE Viticulture and Enology Research Center

2360 East Barstow Avenue Fresno, California 93740-0089 (209) 278-2089

June 24, 1991

Mr. Justin Meyer American Vineyard Foundation P. O . B o x 4 1 4 Oakvi11e, CA 94562

D e a r J u s t i n ,

Enclosed please find the following American Vineyard Foundation final reports for the 1990/91 year.

1. Winemaking Without Sulfur Dioxide-Alternative Treatment - C.J. Muller, K.C. Fugelsang and B.H. Gump

2. Capture & Utilization of Fermentation Emission Volatiles II - C.J. Muller and K.C. Fugelsang

3. Variegated Leafhopper Population Dynamics in Relation to Plant Nitrogen Level and Plant Fertilizer Source: A Nutritional Ecology Study - Mark Mayse and William Roltsch

4. Spiders as Beneficials in Grape Agro-ecosystems - William Roltsch, Mark Mayse and Mbah Njokom

The Viticulture & Enology Research Center appreciates your continued support. If you have any questions please give me a cal 1.

Sincerely, \J . Vincent E. Petrucci, Director Viticulture & Enology Research Center

enclosure

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THE CALIFORNIA STATE UNIVERSITY FINAL REPORT 1990/1991 AMERICAN VINEYARD FOUNDATION June 30, 1991

PROJECT TITLE: Spiders as Beneficials in Grape Agro-ecosystems

PRINCIPAL INVESTIGATORS: Dr. William Roltsch, Dr. Mark Mayse, & Mr. Mbah Njokom Viticulture & Enology Research Center 2360 E. Barstow Avenue California State University, Fresno Fresno, CA 93740-0089 Phone: (209) 278-2089

OBJECTIVES AND TIMETABLES:

A) Determine the primary spider species and their distribution in central San Joaquin Valley vineyards that vary in location or chemical treatment.

B) Determine the seasonal occurrence of the predominant spider species found in grape.

C) Evaluate the ecological role of spiders as natural enemies in grape agro- ecosystems in the central San Joaquin Valley. Seven vineyard sites were sampled from early May to October of 1990. Four vineyards were sampled every two weeks for both spiders and leafhoppers (i.e., variegated and western grape leafhopper). The remaining vineyards were sampled m o n t h l y f o r s p i d e r s .

SUMMARY:

Spiders represent an entirely predacious group of organisms whose potential importance as beneficials in agro-ecosystems has generally been overlooked. The goal of this research was to investigate the potential importance of spiders as a mortality factor for grape insect pests.

Spider populations were sampled at frequent intervals in a number of Fresno County vineyards. Except for one site, all vineyards utilized "soft" pesticide alternatives. Furthermore, the sites represented a range of environments including vineyards near and distant from riparian habitats.

Spiders were abundant in vineyards managed with the use of "soft" pesticides (e.g., B.t. & soaps) in the Fresno County area. Three species in the families Agelenidae and Clubionidae were particularly common. Species in the family Salticidae were less abundant, although consistently present. Spider populations "built" in the canopy and persisted through the growing season with little fluctuation over short time intervals. The relative abundance of spiders in vineyard canopies suggests that they are of considerable potential importance as biological control agents in vineyards, having been grossly overlooked. It is suggested that the negative impact of pesticide use on spider populations may be extensive. Our findings indicate the need for additional research directed at defining the impact that spiders have on specific insect pests of vineyards. In addition, studies are needed to investigate the effects of ground cover management, pesticide use, and other cultural factors on spider population dynamics.

RESEARCH ACCOMPLISHMENTS:

This study demonstrated that vineyards using "soft" pesticide alternatives harbored relatively large populations of spiders. From mid-June to September, populations in such vineyards averaged from 5 to 15 spiders per sample unit (i.e., one drop sheet count) (Fig. 1). However, the vineyard site under conventional pesticide use (i.e., CSU Con.) had a mid-summer peak of only 1.5 spiders per sample unit. Calculation of 95% confidence intervals indicates that sample means are highly reliable (Fig. 2). Because a relative sampling method was used, absolute population density differences among taxa may differ from our findings. However, visual observations of spiders in the canopy did not indicate that large differences occur between drop sheet composition of taxa and actual canopy populations. In comparing leafhopper populations among vineyards, the vineyard under conventional pesticide use (i.e., CSU Con.) had a large late season variegated leafhopper population (Fig. 4). This was not observed in any of the other sites sampled. In fact, the adjacent vineyard section that was under a reduced pesticide use schedule did not exhibit a large late season leafhopper population. This information clearly suggests the need for improved understanding of the impact of pesticide use on spiders, and in turn their impact on leafhopper populations. Collected spiders were predominantly from three families: Agelenidae, Clubionidae and Salticidae (Fig. 3). The common name of species in the family Agelenidae is "funnel-web spider." These spiders build sheetlike webs with an overall funnel shape. The web contains a tubular retreat for the spider. Capture of prey is primarily through the use of the web. The sole species that represented this family was Hololena nedra.

Spiders in the family Clubionidae are called "two-clawed hunting spiders" or "sac spiders." Although they also construct a web (typically tubular in form), it is not used to capture prey. The predominant species represented by this family were Trachelas oacificus. and Chiracanthium inclusum. As the name suggests, clubionids actively hunt for their prey.

Salticidae represented the third family whose species were commonly counted in all vineyards. The smaller overall abundance of this group along with the diversity of species involved made it difficult to accurately quantify each species. One common representative was Metaohidippus manni. Salticid or "jumping spiders" do not build webs, and like the two-clawed hunting spiders they hunt for their prey.

2 , nUTSTDF PRESENTATION OF RESEARCH:

Presented in a symposium at the Entomological Society of America Pacific Branch meeting. Title: "Spider Survey of Central California Grape Agro- ecosystems." Sacramento, CA. June, 1991. Information will also be presented in a chapter of a book entitled: "Enhancing Natural Control of Arthropod Pests Through Habitat Management." To be edited by Charles Pickett and Robert Bugg.

Presented in Ag Alert, a Farm Bureau publication. Title: Arachnophobia may be harmful to your vineyard. March 27, 1991.

Presented in CATI Update newsletter. Title: Spider study could spur new biological controls. March 1991.

R4:5avfbr.rpt WS5/5.25

3 Spider aver./dropsheet

P i l i b o s ( F 1 )

-h- PeteWolf (F2)

Maltre (F3)

-e- CSU Con.(F4)

CSU Min.(F6)

S m e d s 1 ( F 6 )

Smeda 2 (F7)

Julian Dates.

June 1 J u l y 1 A u g . 1

Fig. 1 Average number of spiders (all species combined) by sarapl date in seven vineyard sites in Fresno County, CA during 1990. hnxj ol cpldarc/dropahaal. Ak«r. 0 ol •pldara/dropahaat.

CSU Con. (F4)

ol •ptdore/dropchaal. K/mt.0 ol cpklora/dropahoot.

CSU MIn. (F6) Smeds 1 (F6)

<*l. I o«t. t o

toft J ol •pldora/dropalioat. Akor. # ol •pidoro/dropahoot.

20 140 1S0 lao 200 220 240 260 260 300 120 140 160 180 200 220 240 260 260 300 Julian DatM Julian Datoa lur I Jv t JiJr • *»«. I t**!.! o«i. I o

hmt0 ol apldara/dropahML

Fig. 2 Average number of spiders by sample date in each vineyard site with the corresponding 95% confidence interval. Average value based on 30 dropsheet samples per vineyard on each sample date during 1990.

20 140 160 180 200 220 240 280 260 300 Julian Oatoa

LL.. I .kM t JkIv I ttm. I awL I 0€t I 0 « l . U Apw«r«/d^op•^•«t AMrydrop«li*«L »l )| ^ PoteWolf. CSU Conv. S o l d e r f a n l l l M . S o l d e r l a m l i l e e . —^ A«el«oldw. Aoelenldee^ -H ClublMildM. - + - C l u U e n l d e e . - * r - 0 « I U o M « d SeiUoldee.

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CSU Min. S p i d e r l e m l t l e * . S m e d s 1 s p i d e r ( a m i n e * . — A p e l e n l d e a . — ~ A p e l e n l d e e .

— 1 - C l u M o n l d e e . - + - O u W o n l d e e .

Seltloldee. SeJtteldee.

160 170 160 180 200 210 220 230 240 260 260 270 260 280 300 160 170 160 180 200 210 220 230 240 260 280 270 280 280 300 Julian Data. Julian Data.

July 1 A.I. 1 MfL I del. I O.I. te

^Aaarydrapaliaat AaarydropatiaaL Maltre. Pilibos. S p M e r f a a U l l e * . S p i d e r f a m l l l e a — ~ A « * l « n l d a * — A p e l e n l d a e

-H CtuMdnldaa •+• CluPlontdee H K - S a l M o l d * * - a - S t l t t e l d a *

160 170 160 180 200 210 220 230 240 260 260 270 260 280 300 160 170 160 180 200 210 220 230 240 260 260 270 260 280 300 Julian data*. JuBan data*.

Jehr 1 *«a. I •ept « 0*L I Oel. >e

AMrydropstiaat 0|

S m e d s 2 S p i d e r ( a m i l l e e . Fig. 3 Average number of spiders — A o e l e n l d a * b y f a m i l y g r o u p f o r e a c h v i n e y a r d OuMonldee site during 1990. Saltleldaa

Ol . i . . . ^ . . . . . 1 160 170 160 180 200 210 220 230 240 260 260 270 260 280 300 Julian dalaa.

CAUFORNIA STATE UNIVERSITY» FRESNO

FRESNO. CALIFORNIA 93740-0089

SCHOOL OF AGRICULTURAL SCIENCES & TECHNOLOGY VITICULTURE & ENOLOGY RESEARCH CENTER (209) 294-2089 TELEX 9103501099 CSUFVITICULTR

February 27, 1991

Mr. Justin Meyer American Vineyard Foundation P. O . B o x 4 1 4 Oakville, CA 94562

Dear Justin,

Enclosed please find an interim report for Dr. William Roltsch and Dr. Mark Mayse for their Spiders as Beneficials in Grape Agro-ecosystems research project for 1990-91.

Again, the Viticulture & Enology Research Center appreciates your continued support. If you have any questions please give me a call.

Sincerely, V]

Vincent E. Petrucci, Director Viticulture & Enology Research Center

enclosure

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THE CALIFORNIA STATE UNIVERSITY AMERICAN VINEYARD FOUNDATION

Interim Report 1990-91

March 1, 1991

PROJECT TITLE: Spiders as Beneficials in Grape Agro-ecosystems

PRINCIPAL INVESTIGATORS: Dr. William Roltsch, Mr. Mbah Njokom & Dr. Mark Mayse

ABSTRACT

Spiders represent an entirely predacious group of organisms whose potential importance as predators in agro-ecosystems has generally been overlooked. The goal of this research was to clarify whether or not spiders as a collective group of species have the potential of representing a meaningful mortality factor of grape insect pests.

Spider populations were sampled at frequent intervals in a number of Fresno County vineyards. Except for one site, all vineyards received minimal pesticide inputs. Furthermore, the sites represented a range of environments including vineyards near and distant from riparian habitats.

This survey study indicates that vineyards under minimal insecticide management harbor relatively large populations of spiders throughout the summer growing period. The predominant spider species are from three taxonomic families, known to catch their prey using webs or by actively hunting. Data also suggest that spider populations are suppressed in vineyards where pests are managed through the conventional use of insecticides.

OBJECTIVES

1) Identify the primary spider species and their distribution in central San Joaquin Valley vineyards. An emphasis is placed on vineyards receiving minimal pesticide inputs.

2) Determine the relative abundance and seasonal occurrence of the predominant spider species found in grape.

PROCEDURES

Six vineyards located at widely distributed points in Fresno County were selected for the study. Spider populations in all vineyards were sample monthly from April to October of 1990. Four of the vineyards were sampled biweekly for both spiders and leafhopper nymphs (predominantly the variegated leafhopper). One of the Page 2. "Spiders as Beneficials in Grape Agro-ecosystems"

vineyards was managed by the conventional use of pesticides, although a portion of it was under a reduced pesticide use schedule. Both locations were sampled extensively. All other vineyards were managed with a minimal use of pesticides. Spiders were sampled using a white cloth (4.7 sq. ft) supported by a PVC frame that was held under the grapevine canopy while the vine foliage was vigorously shook. On each sample date 30 vines were sampled in this manner in each vineyard. All spiders were counted and placed in vials containing alcohol. Spider samples were returned to the laboratory and sorted according to taxonomic group. In those vineyards where leafhopper nymph populations were assessed, counts were obtained from two inner and two outer leaves from each of 30 randomly selected vines.

RESULTS

This study demonstrated that vineyards under minimal insecticide use harbored relatively large populations of spiders. From mid- June to September, populations ranged from an average of 5 to 15 spiders per sample unit (one "catch cloth" count). The vineyard site under conventional pesticide use had a mid-summer peak of only 1.5 spiders per sample unit. When comparing leafhopper populations among vineyards, the vineyard under conventional pesticide use had a large late season variegated leafhopper population. This was not observed in any of the other sites sampled. In fact, the adjacent vineyard section that was under a reduced pesticide use schedule did not exhibit a large late season leafhopper population. Although this information is only suggestive, it does point to the need for understanding the impact of pesticide use practices on spiders and in turn their impact on leafhopper populations. Collected spiders were predominantly from three families: Agelenidae, Clubionidae and Salticidae. The common name of species in the family Agelenidae is "funnel-web spider." These spiders build sheetlike webs with an overall funnel shape. The web contains a tubular retreat for the spider. The capture of prey is primarily through the use of the web. Spiders in the family Clubionidae are called "two-clawed hunting spiders." Although they also construct a web (typically tubular in form), it is not used to capture prey. As the name suggests they actively hunt for their prey. Spiders in the family Salticidae were far less common than species of the previous two families. Salticid or "jumping spiders" do not build webs and like the two-clawed hunting spiders they hunt for their prey.

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