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January 1994 Volume 4, Number 1

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January 1994 Volume 4, Number 1 COOPERATIVE EXTENSION UNIVERSITY OF CALIFORNIA January 1994 Volume 4, Number 1 This newsletter is published by the University of California Kearney Plant Protection Group and the Statewide IPM Project. It is intended to provide UC DANR personnel with timely information on pest management research and educational activities in the South Central Region. Further information on material presented herein can be obtained by contacting the individual author(s). Farm Advisors and Specialists may reproduce any portion of this publication for their newsletters, giving proper credit to individual authors. Pete Goodell, Tim Prather, James J. Stapleton, Charles G. Summers, Beth L. Teviotdale Editors IN THIS ISSUE: Seasonal Dynamics of Epiphytic Mycoflora and Insect Vectors Associated with the Summer Bunch Rot Complex of Table Grapes ...................................................................... 1 Deep Plowing for Nutsedge Control......................................................................................................... 4 Occurrence of Moldy Core and Core Rot of Fuji Apple in California....................................................... 5 Abstracts................................................................................................................................................. 7 IPM Notes ............................................................................................................................................ 11 ARTICLES rot in the Central and Southern San Joaquin Valley where table grapes are grown. A major component of this disease complex is sour rot, characterized by a strong SEASONAL DYNAMICS OF EPIPHYTIC acetic acid odor, leakage of berry juice, and the presence MYCOFLORA AND INSECT VECTORS of vinegar flies (Drosophila spp.) and dried fruit beetles ASSOCIATED WITH THE SUMMER BUNCH (Carpophilus spp.). Diplodia natalensis (syn. ROT COMPLEX OF TABLE GRAPES Botryodiplodia theobromae Pat.) was reported to be the Roger A. Duncan and James J. Stapleton, U. C. Kearney primary causal agent of the summer bunch rot complex Agricultural Center on 'Thompson Seedless' grapes (3). B. theobromae reportedly infects berries at bloom and remains dormant The summer bunch rot complex (caused by species of until the berries begin to mature. When growth of the Aspergillus, Penicillium, Botrytis, Rhizopus or other fungus resumes, breaks in the skin of the berry occur, fungi alone or in combination with Acetobacter and exposing the internal tissues to infection by secondary several yeast species) is the most prevalent form of bunch organisms including species of Acetobacter, Aspergillus, University of California and the United States Department of Agriculture cooperating Cooperative Extension •Agricultural Experiment Station •Statewide IPM Project This material is based upon work supported by the Extension Service, U.S. Department of Agriculture, under special project section 3(d), Integrated Pest Management KAC Plant Protection Quarterly January, 1994, Volume 3, Number 1 Page 2 Penicillium, and Rhizopus. Several yeast species are insects were monitored for growth of fungi. Fungal taxa also associated with the sour rot complex. These growing from plated insects were identified and recorded organisms can also gain entry through mechanical cracks, for each species. Insects captured from the field were wounds caused by insect or bird feeding, or cracks also released into large glass jars containing small caused by powdery mildew [Uncinula necator (Schwein.) clusters of surface-sterilized, wounded and nonwounded Burrill] or other diseases (2). When wounded berries are 'Thompson Seedless' berries. Jars were incubated at 23 + colonized by Acetobacter spp., acetic acid is produced, 1 C and monitored for development of disease. attracting Drosophila flies which in turn may serve as vectors to further spread the disease (3). Results The role of individual fungal species in the summer bunch Seasonal dynamics of epiphytic fungi (Fig. 1) were rot complex is not fully understood. Many of these fungi similar to those found in a study of fungal dynamics of are opportunists, able to colonize only wounded berries, wine grapes treated with leaf removal in the San Joaquin while others are able to initiate primary infection. In Valley conducted in 1990-93 (1). Several taxa of fungi order to obtain a better understanding of the development were recovered. Cladosporium spp. were the most of summer bunch rot complex on table grape varieties prevalent, with Penicillium, Aspergillus, Alternaria, and other than 'Thompson Seedless', population dynamics of Botrytis spp., respectively, also very commonly epiphytic fungi on grape berries were monitored biweekly recovered. All are involved in the development of from June until harvest. Fungi present on the surface of summer bunch rot. Propagules of fungi generally were grape berries were identified and quantified. low early in the season, while numbers of Aspergillus Relationships between population densities of commonly spp. (mostly A. niger) and Penicillium spp. usually recovered fungi and incidence and severity of bunch rots increased rapidly later in the season after veraison. Yeast were examined. Insects associated with sour rot were populations increased dramatically just prior to harvest. captured from diseased clusters in the field and surveyed Compared to other fungal taxa, Botrytis spp. populations for fungal propagules carried on or in their bodies and for were generally very low. Botryodiplodia theobromae, transmission of inoculum to wounded or nonwounded the fungus reputed to be the major cause of sour rot and grape berries in the laboratory. the summer bunch rot complex on 'Thompson Seedless' was not commonly recovered from any of the sampled Materials and Methods vineyards although all vineyards developed some degree of sour rot and summer bunch rot by harvest. Berries from 'Thompson Seedless', 'Ruby Seedless', and 'Red Globe' vineyards in Fresno, Tulare, and Kern Sour rot and rot caused by A. niger were the most Counties were collected biweekly throughout the growing prevalent forms of bunch rot encountered in all of the season. Berries were transported to the laboratory in ice vineyards (Fig. 2). While incidence of sour rot was often chests, placed in polyethylene bottles containing a buffer greater than 25%, Botrytis rot incidence was never more solution, and shaken on a mechanical shaker for 1 hour. than 5%. Correlation between epiphytic mycoflora Aliquots of wash solution were plated onto agar media recovered during the season and incidence and severity of (acidified potato dextrose agar + Igepal surfactant) and bunch rots at harvest were rarely significant. In general, incubated in the laboratory at 23 + 1 C. After 5-7 days, 'Red Globe' vineyards tended to have the lowest incidence fungal colonies were identified, enumerated, and recorded and severity of bunch rots at harvest. Due to the loose as colony forming units (cfu) per cm2 of berry surface. architecture of the clusters of this variety, fungi tended to At the time of harvest, 25 clusters from each replication remain confined to the diseased berries and did not tend to (150 clusters per vineyard) were evaluated for incidence move to adjacent "sound" berries. Summer bunch rot and severity of various rots. The 'Thompson Seedless' tended to be most severe in 'Thompson Seedless' trial in Kern County was harvested by the grower before vineyards. Rot in 'Ruby Seedless' vineyards was variable rot data could be collected. with higher incidence of bunch rot in Tulare County where the vineyard had a higher level of powdery mildew Insects associated with sour rot/summer rot were and many split berries and very low rot incidence in the captured in the field by placing polyethylene bags around Fresno County 'Ruby Seedless' vineyard. clusters affected with sour rot and gently tapping the clusters, causing insects to fall into the bags. Three insect species were consistently recovered from Nonsurface-sterilized insects or insects surface sterilized clusters of 'Thompson Seedless' affected with sour rot in in a 10% bleach + 0.1% Tween 20 solution were plated a vineyard at the Kearney Agricultural Center. These on agar media and incubated at 23 C or 30 C. Plated were dried fruit beetles (Carpophilus hemipterus and C. KAC Plant Protection Quarterly January, 1994, Volume 3, Number 1 Page 3 freemani) and vinegar flies (Drosophila sp.). All insects chemical disease markers. Applied and carried yeast, Aureobasidium, Aspergillus (mostly A. Environmental Microbiology. 53:571-576. niger), Penicillium, and Cladosporium spp., as well as Mucor sp. Colonies of yeast and Aureobasidium grew 3. Hewitt, W.B. 1974. Rots and bunch rots of grapes. from surface-sterilized insects. Insects captured from Calif. Agric. Exp. Stn. Bull. 868. 52 pp. clusters with sour rot transferred fungal propagules from the field, vectoring disease on wounded berries in the laboratory (Fig. 3). Insects preferred to feed on wounded (Figures Not Available) berries and disease was rarely spread to nonwounded berries when wounded and nonwounded berries were placed in insect cages together. When not given a choice, DEEP PLOWING FOR NUTSEDGE CONTROL insects fed on and injured nonwounded berries. Tim Prather, Kurt Hembree and Michelle LeStrange, Carpophilus spp. appeared to be better vectors of fungal U. C. Kearney Agricultural Center and Tulare Co. contaminants to wounded berries while Drosophila flies mainly vectored sour rot. Plowing to bury weed seeds or other
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    "#$% / ! / / / Uncinula necator (Schw.)Burr. !&' () * )+() ,- . !.0 (! * 1! 23 456 @ *!>.6? < :=0! *2 5 9:!.+ 6;. < 9:*! *!7 9" . 7 8 52 5AB 23 456 5E! * H;! * GI ! J-+ G; 5I / !&' () * D )+() ,- . F G ,D >E C;! * O) /A G Uncinula necator (Schw.)Burr.!&' () 5 M K* G N; ( < ! . .K.' H! !.0 (! * 1! 1(O* SO+ U. necator DRAM .5 5;* !.O0 (! * GOI * O. Q; * O1! P!0 8* DGO!7 XW#V O GO 7 DG 0 1! 23 456 D C()U 95 M 7 DG!7 5 ! 5 TT.'R! C;.( .5*. () * DG0 D[. * 9 D[ . 5 /A+ D)+() 5?* #TWZT ! , .55 .D Y .( ( .5O* (! !* GO .'R! 1(* * .( Q; ! , '5 G * 9D* /' D G!7 5 \ * * RAM !] ! D G * ^ _ * 5 !*G1 D[ . J3 D )+() ! K;*! + . ! ! * =? G DRAM * K ; ,D N;5+ G DRAM G!7 I 95* G!7 G * ^ EA .A D` J3 * + . 5?*"a G K;*! C;* . D * K ; ,;!]! N;5+ G 5 6! /;! ! ! * .6? 58* 5 6! /;! ! + * _ \ * * D c AM C()A !. * K ; ,D * C;! * b!* G DRAM PM /) (E .5 .5 /;! ! * .' :/a () * .' # G ]; E * .' T * 58 ! DRAM ;! .* .' "/e !] G G * (! d 6+! () * 1()A .!. * Dc AM \!;* K - ,D !] C;.( G 5 hU 5D* GI ! J-+ G; ! G ! M ,- G 5 = g! I \5;. D[ . fI DRAM .5 !.0 (! D () + * U. necator !&' () ?! /A D)+() 1! 923 456 9!&' () 9RAM 9)+() : 5 Di! '(" ) !" #$$%& . 0 ) (& ,/". ) !" ,'*". )*+ ,- . "#$% / ! / / .(WC WR )R )C) '9. '. 3/. %5 6'7 A S* G 5- 9' n+ 4= V$G& 4 ! 39+ 8 U. necator 2 3& 4 )3/. %5 6'7 '9& S:N U = KF.
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