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BIOLOGICAL
CONTROL OF ARTHROPODS IN GRAPES
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Introduction Vitis vinifera L.,
the most widely cultivated species of grape, had been grown in Asia Minor between
the Caspian and Black seas since the beginning of civilization (Winckler et
al. 1974), flourishing especially in central Europe through the 14th Century.
The invasion of grape phylloxera, Daktulosphaira
vitifoliae (Fitch) from
North America ca. 1886 markedly reduced the productive acreage in France, a
plague that gradually spread to the Black Sea area within 10 years.
Viticulturists were formed to develop resistant rootstocks and hybrid grapes
that greatly sophisticated the industry (Gonzalez 1983). In the some 10
million hectares of grapes worldwide, hundreds of clonal selections and
hybrids have been produced to adapt varieties to various climatic and soil
conditions found on all continents (Gonzalez 1983). Such diverse viticulture
modifies vine microclimates to favor or inhibit pests that are indigenous to
the ecosystem of the grape plant. These various ecological niches created by
the biocenosis of the vine are occupied in each grape region by different
pests (Bournier 1976). As pest resistance to synthetic organic pesticides
developed, there has been an interest in biological control (Flaherty et al.
1985, Flaherty & Wilson 1999). In a review of arthropod pests attacking grapes, Flaherty
& Wilson (1999) consider major taxonomic groups as follows: Cicadellidae.--There are nine species of leafhoppers that attack grapes
(Bournier 1976). Erythroneura
elegantula Osborn, the grape
leafhopper, is the most common. Damage is caused by leaf chlorophyll reduction,
vine defoliation, and damage of the surface of table grapes with excrement,
and annoyance from leafhoppers to workmen (Jensen & Flaherty 1981a). It was observed that grapes planted near streams and rivers,
where wild blackberries, Rubus
ursinus Chamisso &
Schlecht and Rubus procerus Mueller, grow, do not
sustain high grape leafhopper densities (Doutt & Nakata 1965, 1973).
Principal reasons were the activity of Anagrus
epos Girault parasitizing
the eggs of both grape and blackberry leafhopper (Dikrella californica
(Lawson)), a non economic species whose eggs are present year round on wild
blackberries. This synchrony of blackberry leafhopper, grape leafhopper and A. epos phenology was reported by Williams (1984). There was then considerable effort to establish effective
blackberry refuges near commercial vineyards. However, successful control was
not attained because overwintering numbers of A. epos
were so few due to low D. californica egg production in
winter (Flaherty et al. 1985). Effective overwintering of the parasitoid
depended on continuous production of eggs by D. californica.
Williams (1984) found a reproductive diapause in females of this species
during winter. The importance of alternate host plants sustaining leafhoppers
was reported by McKenzie & Beirne (1972), Kido et al. (1984) and Flaherty
et al.(1985). Such host plants as apple, wild rose and French prune are
important host plants for such leafhoppers. In the San Joaquin Valley of
California, there is not an emphasis on the prune leafhopper, Edwardsiana prunicola (Edwards), as a major
overwintering host of the parasitoid (Flaherty et al. 1985). Another species,
Typhlocyba pomaria McAtee, on apple is
also probably important. Jensen & Flaherty (1981a) discuss how the parasitoid, A. epos importance varies with grape variety and its intended
usage. High populations of grape leafhopper can be tolerated on Thompson
Seedless grapes which are to be used for raisin or wine production, but only
very low tolerance is on grapes grown for fresh market consumption. Spotting
damage, which results from leafhopper feces, affects the value of the crop.
On the table grape varieties Emperor and Ribier, the grape leafhopper
populations increase to such high numbers even in the presence of the
parasitoid, that control is unsatisfactory. Reasons for the parasitoid's
greater effectiveness on Thompson Seedless are unknown, but some observations
indicate that the smooth leaf surface of Thompson Seedless vines does not
impede searching and oviposition of the parasitoid. Early maturing varieties
also produce fewer newly mature leaves, sites which are favored by grape
leafhopper for egg deposition. By comparison the later varieties such as
Emperor and Ribier have tomentose (hairy) leaves that may interfere with the
parasitoid. Leafhopper oviposition is also favored by the development of
newly matured leaves late in the season. Later season irrigation in such
vineyards also favors grape leafhopper (Jensen & Flaherty 1981a). The parasitoid, Aphelopus
albopictus Ashmead (= A. comesi Fenton) attacks all instars of the grape leafhopper
(Cate 1975). Parasitoid eggs are placed between the nymph's 2nd and 3rd
abdominal segments where they remain undeveloped until the nymph molts to the
adult stage. The host appears normal during the parasitoid's larval
development except for an elongating larval sack (the thylacium) that
gradually protrudes from the abdomen with each parasitoid mold. By its 5th
instar the parasitoid has developed mandibles and eviscerates the adult leafhopper.
Prior to evisceration the adult leafhopper is functionally non-reproductive
since gonads fail to develop in parasitized adults. Parasitism is usually
between 10-40%, but Cate (1975) reported a high of 77%, and speculated that
cultural practices might be altered to favor parasitism. The variegated grape leafhopper, Erythroneura variabilis
Beamer, is the principal vineyard pest in the lower Sonoran Desert of
California, Arizona and Mexico. Infestations are severe in the Coachella
Valley of California where the high temperatures allow for rapid development
and as many as six generations per year (Barnes 1981). Activity of the
parasitoid A. epos is low in this climate,
becoming prominent only in the milder climates of the coastal plain where
parasitism can reach 90% (Barnes 1981). Variegated grape leafhopper invaded the San Joaquin Valley
around 1980 and continues to spread. Defoliation occurs in Thompson Seedless
vineyards especially where the grape leafhopper had been under good control
by A. epos. The whole management strategy, built around the
activity of this parasitoid, was altered with a renewed attention to chemical
control. This caused outbreaks of secondary pests such as spider mites and
mealybugs. The projected annual costs for control of variegated grape
leafhopper were expected to be >$5-10 million, with yield and quality
losses probably double that amount (Wilson et al. 1986, 1987). Settle et al. (1986) commented "Variegated leafhopper is
a more serious pest than the grape leafhopper, in part because of differences
in egg-laying behavior. Variegated leafhopper eggs, deeply buried within the
leaf tissue, are less likely to be detected by A. epos
than grape leafhopper eggs, which stand out as blisters on the leaf
surface." A search for new parasitoids of variegated grape leafhopper
was begun in 1985 in southern California, Arizona, Colorado, Texas, New
Mexico and Mexico. The variety of species and biotypes of leafhopper
parasitoids collected from diverse climatic zones and in different seasons were
found (Gonzalez et al. 1988). It was found that A. epos
had evolved a wide range of biotypes, differing in relative preference for
the grape leafhopper and variegated grape leafhopper. Pickett et al. (1987)
indicated that the San Joaquin Valley biotype had a 6.9X greater preference
for grape leafhopper than for variegated grape leafhopper. On the basis of
preference, biotypes from the Coachella Valley and Colorado would
respectively choose, provided equal numbers of eggs of both hosts, 2-4.3
times more variegated grape leafhopper eggs. Erythroneura ziczac Walch
is the most important insect on grapes in the Okanagan Valley, British
Columbia (McKenzie & Beirne 1972). Two cultural procedures which
prevented damage by leafhoppers were (1) destroying overwinter sites around
the vineyards and (2) providing A.
epos Generalist predators, primarily spiders such as Theridion sp., may
significantly impact leafhoppers in vineyards with cover crops (Settle et al.
1986). In San Joaquin Valley studies, twice as many spiders were recorded in
a vineyard with a weed cover crop. Settle et al. (1986) also found that
Thompson seedless grapes grown on its own roots showed greatly reduced
attractiveness to leafhoppers, resulting in a nearly 8X reduction in
leafhopper numbers compared with the more vigorous vines on Saltcreek
rootstock. Reduced leafhopper pressures afforded by cultural practices
suggest a potential for biological control. Pierce’s Disease spread by sharpshooter leafhopper
[Please refer to ch-120.htm] Pseudococcidae.--Two mealybug species causing problems in California
vineyards are the grape mealybug, Pseudococcus
maritimus (Ehrhorn) and the
obscure mealybug, Pseudococcus
affinis (Mackell) (= P. obscurus Essig). The first species is principally a pest
of table grape varieties whose bunches make contact with vine bark and become
infested (Flaherty et al. 1981b). Before the late 1940's occasional losses
occurred in table grapes, which were mostly spotty and generally
nonproblematic. The problem gradually increased in the late 1940's with
extensive use of DDT and other pesticides to control grape pests. The obscure
mealybug, which has been recorded on a large number of hosts, was recently
found to be a problem in unsprayed vineyards in San Luis Obispo County, a
more coastal climate. The absence of effective parasitoids attacking obscure
mealybug points to it as a recently introduced species that will require the
importation of new natural enemies. Clausen (1924) reported five primary endoparasitoids from
grape mealybug in the central San Joaquin Valley, where late summer and
autumn parasitism was >90% in 1919. Flaherty & Wilson (1999)
reexamining Clausen's (1924) data concluded that Zarhopalus corvinus
(Girault) was the most active. In the 1960's a ranking of host parasitism
from samples of Doutt & Natata (unpublished) showed that Acerophagus notativentris (Girault) was the
principal species, that Acerophagus
subalbicornis (Girault) was
occasionally found and that Z.
corvinus was uncommon
(Flaherty et al. 1976). Parasitoids were not reared from mealybug samples
collected from an Emperor variety vineyard where heavy treatments. of
pesticides were made. Another mealybug, Maconellicoccus
hirsutus (Green), is a pest
of grape in India (Manjunath 1985). It attacks the varieties Thompson
Seedless, Anab-e-Shahi and Bangalore Blue. Up to 90% of the clusters are
destroyed, and chemical control is not effective. The encyrtid, Anagyrus dactylopii Howard, seems to offer some biological control
potential. In late season samples at Bangalore, parasitization ranges from
60-70%, although fields are regularly treated with insecticides. Manjunath
(1985) recommended the introduction of Anagyrus
kamali Moursi and Prochiloneurus sp. which
reportedly give complete control of M.
hirsutus in Egypt (Kamal
1951). Planococcus citri
(Risso) damages >20 species of plants in the Soviet Union (Niyazov 1969).
The parasitoid Anagyrus pseudococci (Girault) is active
in the region, destroying up to 75% of the host populations in untreated
areas. Allotropa mecrida (Walker) was
responsible for 20% parasitism of P.
citri in Turkemenia and
Georgia. The encyrtids Leptomastidea
abnormis (Girault) and Leptomastix dactylopii Howard were
introduced into Georgia and Turkemia from the United States in 1960, but
native hyperparasitoids reduced their effectiveness. In Transcaucasia and
Soviet Central Asia, Thysanus
(Chartocerus) subaeneus Forster was
responsible for up to 20% hyperparasitism of A. mecrida.
Rzaeva (1985) reported that L.
abnormis successfully
established on Planococcus ficus Signoret, a mealybug pest
of grapes in eastern Transcaucasus. The introduction of Clausenia josefi
Rosen also was recommended (Niyazov 1969), as well as A. notativentris
from California. The effectiveness of predators in California vineyards is
generally unknown. Mealybug egg masses have been attacked by cecidomyiid fly
larvae (Flaherty et al. 1982). Adults of Chrysoperla
spp. (= Chrysopa spp.) are
often abundant on grapevines with mealybugs, adults being attracted to
mealybug honeydew. Cryptolaemus
montrouzieri Mulsant (the
mealybug destroyer) is rare in California vineyards. The use of this predator
for mealybug control in the Soviet Union was reviewed by Yanosh &
Mjavanadze (1983). Cryptolaemus
was particularly effective on Chloropulvinaria
floccifera Westwood on tea,
with adult beetles being field released. Niyazov (1969) reported that one of the
most effective predators of mealybugs on grape in the Soviet Union was C. montrouzieri which had been introduced from Egypt in 1932.
Other coccinellids of importance in Turkemenia were Coccinella spetempunctata
L., Scymnus apetzi Mulzant, Hyperaspis polita Weise, Scymnus
subvileosus (Goeze), Nephus bipunctatus Kugelann and Scymnus biguttatus
Mulsant. Larvae of Leucopis
(Leucopomya) alticeps Czerny and Chrysoperla carnea (Stephens) were active
on all mealybug stages. The coccinellids were parasitized by Homalotylus sp. and the
chrysopids by Telenomus acrobates Girard. Coccidae.--Gonzalez
(1983) reported that grape quality can be affected by copious amounts of
honeydew produced by Parthenolecanium
persicae (F.) in Chile, but
natural enemies are important in minimizing damage. The principal parasitoids
were Coccophagus caridei (Brethes) and Metaphycus flavus (Howard). These and other parasitoids were common
natural enemies of lecanium coccids on other plants including P. corni (Bouché) which is also a pest of grapes in Chile. Phylloxeridae.--The coccinellid Scymnus
cervicalis Mulsant is the
only natural enemy considered important as a predator of the leaf-feeding
form of grape phylloxers, D.
vitifoliae, on wild grapes
in Erie County, Pennsylvania (Wheeler & Jubb 1979). Tetranychidae.--Spider mites became serious grape pests after World War II,
at the same time that synthetic organic insecticides appeared (Flaherty et
al. 1985). Two spider mite species which are commonly found on California
grapes are the Pacific spider mite, Tetranychus
pacificus McGregor, and the
Willamette spider mite, Eotetranychus
willamettei (Ewing)
(Flaherty et al. 1981a). Two-spotted spider mite, T. uriticae
Koch. is rare on grapes in California. In the eastern United States, European red mite, Panonychus ulmi (Koch), is the principal spider mite problem (Jubb et
al. 1985). This species is also a pest in Europe. Schruft (1986) listed E. carpini vitis
Boisduval, T. urticae, T. mcdanieli
McGregor and T. turkestani Ugarov &
Nikolski also as pests in Europe. Oligonychus
vitis Zaher & Shehata
was reported serious on grapes in Egypt and Chile (Rizk et al. 1978, Gonzalez
1983). In the Soviet Union spider mite pests are P. ulmi, Eotetranychus pruni (Oudemans), T. turkestani and Bryobia
praetiosa Koch . Schruft
(1986) reported that E. pruni is important as a pest in
Bulgaria. In India there are four species, Oligonychus. mangiferus
(Rahman & Sapra), O. punicae (Hirst), T. urticae, and E.
truncatus Estebanes &
Baker (Schruft 1986). In Japan grapes are hosts for B. praetiosa,
E. smithi Pritchard & Baker, T. kanzawai
Kishida and T. urticae (Schruft 1986). In San Joaquin Valley, California vineyards, the most
important natural enemy of spider mites us the predatory mite Metaseiulus occidentalis (Nesbitt)
(Flaherty et al. 1981a). Amblyseius
californicus (McGregor) is
important in the Salinas Valley and M.
mcgregori (Chant) in the
Sacramento Valley. Although these predators prey on the Willamette spider
mite, their effectiveness is unknown. In the eastern United States the most
common predatory mites on Concord grapes (Vitis
labrusca L.) are the
phytoseiids, Neoseiulus (Amblyseius) fallacis (Garman) and Amblyseius andersoni (Chant), and the stigmaeid Zetzellia mali
(Ewing). Neoseiulus fallacis and Z. mali may be important in natural control of P. ulmi (Jubb et al. 1985). In Europe the cost common
phytoseiids are Typhlodromus
pyri Scheuten, Euseius (Amblyseius) finalndicus
(Oudemans), Amblyseius aberrans (Oudemans) and A. andersoni, but only T.
pyri is of importance in
biological control (Schruft 1986). However, A. aberrans
is very important in Italy (Gambaro 1972). Rizk et al. (1978) reported that Agistemus
exsertus Gonzalez, Amblyseius gossipi El-Badry and Tydeus
californicus (Banks) are
very abundant in middle Egypt, while in Chile Amblyseius chilenensis
(Dosse) is very important (Gonzalez 1983). Spider mite control
can be somewhat predicted by the ratio of the number of predators to
spider mites. For any system there exists a particular predator/prey ratio at
which the pest population will be controlled. For example, Tanigoshi et al.
(1983) reported that a 1:10 ratio of Neoseiulus
fallacis to P. ulmi provided control in Red Delicious apples. In another
orchard with a different apple variety, Tanigoshi et al. (1983) found a 1:20
ratio was sufficient, and indicated that relatively fewer predaceous mites
were required to provide control as a result of reduced spider mite fecundity
on this variety. Wilson et al. (1984)
found that a 1:11 ratio of Metaseiulus
occidentalis to Tetranychus spp. provided
control in almonds within two weeks when the spider mites were at densities
of >5 mites per leaf. At lower densities an increasingly higher
predator/prey ratio was required. It is very tedious to estimate spider mite abundance and
predator effectiveness, because mites are extremely small, and often
numerous. Schruft (1986) found that it is possible to estimate the risk of
damage by P. ulmi or E. carpini
vitis using a method developed
by Baillod et al. (1979). The method tests the relationship between the
number of spider mites per leaf and the proportion of leaves in a sample
occupied by mites. Therefore, instead of counting the mites themselves, the
number of leaves with one or more mites is recorded. The same sampling
procedure has been used to evaluate predaceous mites (Baillod & Venturi
1980). Flaherty et al. (1981a) used an infested leaf (binomial) predator/prey
ratio, together with information on the relative level of spider mites in the
vineyard. Based on observations over several years, they found that a 1:2
(0.5) binomial ratio of predator to spider mite infested leaves was
sufficient for control. This ratio was less conservative than the ratios
derived using the Wilson et al. (1984) procedure for almonds. A binomial
ratio of ca. 1:1 is equivalent to a 1:10 count ratio at densities between
15-50 spider mites per leaf. A binomial ratio closer to that reported by
Flaherty et al. (1981a) was calculated when using a 1:20 count ratio . The
lower ratio for grapes may indicate a lowered reproductive capacity for
spider mites on grapes compared to that found on almonds, or perhaps for that
found by Tanigoshi et al. (1983) on apples. Alternate foods of predaceous mites have been considered in predator/prey
relations. Flaherty (1969) reported that M.
occidentalis was better able
to regulate low densities of Willamette mites in the presence of small number
of T. urticae that moved from weeds onto grape leaves. Flaherty et
al. (1981a) recommended that Willamette spider mite be considered as an
important alternate prey because it is a much less serious pest of grapes
than Pacific spider mite. Metaseiulus
occidentalis also preys on
other mites, such as tydeids, eriophyids and perhaps tarsonemids. In Europe
additional food for T. pyri includes eriophyids,
tydeids, pollen and pearls of the grape (Schruft 1972). The possible benefits
of augmenting pollen feeding tydeids by pollen applications or planting cover
crops that produce wind borne pollen exists (Flaherty & Hoy 1971, Calvert
& Huffaker 1974). Gambaro (1972) reported that Amblyseius aberrans
was able to live and reproduce in the absence of prey and thus could maintain
spider mite populations at low densities. Viticultural practices influence spider mite outbreaks (Flaherty et al. 1981a).
Emphasis is placed on avoiding problems associated with low vine vigor, dusty
conditions and water stress, which can greatly increase the chance of Pacific
spider mite outbreaks. Although 10 species of phytoseiid mites are known in
commercial vineyards of the San Joaquin Valley, only M. occidentalis
seems to pay a significant role in natural control of spider mites (Flaherty
& Huffaker 1970). The predaceous mite Amblyseius
nr. hibisci becomes abundant
where triadimefon replaced sulfur for control of powdery mildew, Uncinula necator Burrill. The predaceous mite is common in wild
grapes where sulfur is not applied (Flaherty et al. 1985). English-Loeb et
al. (1986) showed that A.
nr. hibisci was not only the
dominant phytoseiid species where sulfur was not applied but it also
maintained lower numbers of Willamette spider mites than M. occidentalis
where sulfur was used. The phytoseiid Typhloseiopsis
smithi (Schuster) was also
recorded on non sulfur treated grape foliage (English-Loeb et al. 1986). Arthropod predators, such as predaceous insects and spiders, are considered as
ineffective natural enemies of spider mites (Flaherty et al. 1981a), because
they appear too late in the season or increase in numbers too slowly.
However, their contribution to natural control in vineyards might be
significant. Sometimes six-spotted thrips, Scolothrips sexmaculatus
(Pergande) destroys Pacific spider mite populations. This predator is
unpredictable, however, which may be related to periodic low prey densities.
In Italy anthocorids and coccinellids are considered effective at high prey
densities (Duso & Girolami 1985). Schruft (1986) reported that predaceous
insects, Scymnus sp., Oligota sp., Scolothrips longicornis Priesner, Anthocoris nemorum (L.) and Orius
minutus (L.) are found on
grapes infested with P. ulmi, but their importance for
biological control of red spider mite populations is unknown. However, it is
certain that some chrysopids, particularly Chrysoperla carnea,
are effective predators of red spider mites during summer and late autumn
(Schruft 1986). Spider mite control by insect predators may be subtle as well
as important, because observations in vineyards and laboratory studies
revealed that western flower thrips, Frankliniella
occidentalis (Pergande)
which is a pest of grapes, feeds on Pacific spider mite eggs and may actually
affect the pest's population in vineyards (Flaherty et al. 1981a). Franklineilla occidentalis predation is apparently
also important in cotton on spider mites (Gonzalez et al. 1982, Gonzalez
& Wilson 1982, Trichilo 1986). Mass releases of M.
occidentalis for control of
Pacific spider mites are not practical (Flaherty et al. 1985), but an autumn
release program may be more useful. Flaherty & Huffaker (1970) showed
that late season predator activity in vineyards is essential to spider mite
balance. A fall release of M.
occidentalis resulted in
excellent biological control of Willamette spider mite the following spring
and summer. Hoy & Flaherty (1970, 1975) considered late season diapause
induction important for the successful overwintering of M. occodentalis
populations. Flaherty et al. (1985) thought that a fall release of predators
reared under diapausing conditions would minimize the timing and survivorship
problems associated with early summer releases because immediate control of
Pacific spider mite in the fall is not a factor and diapausing predators
require little food. In Italy, Girolami & Duso (1985) reported on the
establishment of predator/prey equilibrium in pesticide-disturbed vineyards
with reintroductions of A. aberrans. Baillod et al. (1982) described methods for reintroduction of T. pyri into vineyards in Switzerland and recommended their
use for biological control of phytophagous mites. Schruft (1986) reported the
artificial release of T. pyri by the introduction of
infested canes or foliage. Tenuipalpidae.--Brevipalpus
chilensis Baker is serious
on grapes in Chile, which developed as a consequence of indiscriminate use of
pesticides (Gonzalez 1983). Important to consider preserving is the
predaceous mite A. chilenensis. In Victoria,
Australia, B. lewisi McGregor causes a
superficial scaring of bunch and berry stems (Buchanan et al. 1980). A close relationship
between B. lewisi and its most common
phytoseiid predator Amblyseius
reticulatus (Oudemans) did
not reveal regulation of B. lewisi numbers by A. reticulatus during the growing season. However, large
numbers of A. reticulatus during the end of the
growing season may reduce the number of B.
lewisi that can overwinter.
The false spider mite Tenuipalpus
granati Sayed has been
considered a serious pest of grapes in Egypt (Rizk et al. 1978), which was
blamed mostly on pesticide upsets. The predators Agistemum exsertus,
Amblyseius gossipi and Tydeus californicus were observed to be associated with T. granati. Eriophyidae.--The eriophyid mite Colomerus
vitis (Pagenstecher) attacks
various species and hybrids of grapes. Different biotypes of the eriophyid
have been found in California, separated by injury type (Kido 1981). The
phytoseiid mite M. occidentalis was reported
effective in reducing populations of C.
vitis. Schruft (1972) reported
that C. vitis and Calepitrimerus
vitis (Nalepa) also
eriophyid pests in Europe, were destroyed by the tydeids Tydeus götzi
Schruft and Pronematus stärki Schruft. Tortricidae.--Grape clusters are often attacked by tortricids worldwide.
The orange tortrix, Argyrotaenia
citrana (Fernald), is a
major pest in cooler coastal regions of California. Larvae cause damage by
feeding in grape clusters and permitting rots to invade (Kido et al. 1981c). Kido et al. (1981b) assessing biological control sampled Gamay Beaujolais
vines in Salinas Valley vineyards. One vineyard (Soledad) had a history of
injurious infestations that required treatments. The other (Greenfield) had
very light infestations and no treatments were required. Samples of clusters
from the Greenfield vineyard contained few orange tortrix larvae and pupae,
with 53.5% parasitism, while the Soledad vineyard with a high orange tortrix
density had 16% parasitism. Exochus
nigripalpus subobscurus Townes was the
predominant parasitoid in both vineyards. Apanteles
aristoteliae Viereck was
less frequent. The coyote brush, Baccharis
pilularis DeCandolle also
sustained orange tortrix infestations. Large numbers of another tortricid
species Aristoteliae argentifera Busck were found on
coyote brush located near the Greenfield vineyard and several parasitoids
were recovered from larvae and pupae (Exochus
sp. and Apanteles sp.).
Coyote brush was much less abundant near the Soledad vineyard and consisted
mainly of young plants and no infestation of A. argentifera. The omnivorous leafroller, Platynota
stultana Walsingham, has
become a major pest in the warmer inland valleys of California since 1960
(Kido et al. 1981a). It causes a rot similar to that of the orange tortrix. A
number of insect parasitoids have been recorded on omnivorous leafroller in
vineyards, but parasitoids seldom accounted for >10% mortality even on
very high worm infestations. Flaherty et al. (1985) recommended the importation
and augmentation of natural enemies of this insect in the San Joaquin Valley. Trichogramma spp. have been mass released to augment biological control of
omnivorous leafroller and orange tortrix. Makhmudov et al. (1977) reported
that Trichogramma sp.
releases gave good control of Lobesia
botrana (Schiff), a
tortricid attacking grapes in the Soviet Union. Marcelin (1985) reported
significant reductions of L.
botrana and Eupoecilia ambiguella (Hübner) populations with Trichogramma sp. releases. The selective control of
tortricids in grapes with Bacillus
thuringiensis Berliner and
mating disruption has been stressed in Europe. Damage by Proeulia
auraria (Clarke) was
reported from Chile by Gonzalez (1983) when natural enemies were destroyed by
pesticides. A complex of five species of egg and larval parasitoids are
associated with this pest. The encyrtid, Encarsia
sp. attacked eggs. Larval parasitoids included eulophids Elachertus and Bryopezus,
a braconid Apanteles, and
unidentified ichneumonid, and a tachinid, Ollacheryphe
aenea (Aldrich). The western grapeleaf skeletonizer, Harrisina brillians
Barnes & McDunnough, was originally distributed throughout the
southwestern United States and northern Mexico. It was first found in
California in San Diego in 1941, where it severely defoliated wild grapes, Vitis girdiana Munson in the canyons. Soon it became a serious
pests in commercial vineyards. The larvae are voracious feeders and can
devastate a crop by defoliating an entire vineyard. In 1950 efforts were initiated in the University of California
to control grapeleaf skeletonizer biologically. Parasitoids were introduced,
with two species, the braconid, Apanteles
harrisinae Muesebeck and the
tachinid, Ametadoria miscella (Wulp) (= Sturmia harrisinae Coquillett) predominating (Clausen 1961). A
virulent granulosis virus was also accidentally introduced. Surveys in San Diego County in 1982-1983 revealed that it was
necessary to spray grapeleaf skeletonizer in commercial vineyards (Flaherty
et al. 1985). Abandoned untreated vineyards and backyard vines were severely
defoliated despite the activity of the imported parasitoids. Symptoms of
virus infection were not observed in the survey. Grapeleaf skeletonizer was
not found in wild grapes, V.
girdiana, except where they
were in close proximity to heavily infested commercial V. vinifera
vineyards. The skeletonizer invaded the San Joaquin Valley in 1961
(Clausen 1961), and new infestations appeared thereafter throughout the
Central Valley in spite of eradication efforts. Renewed efforts to introduce
natural enemies were made in the 1980's, which resulted in the translocation
of parasitoids from southern California and the acquisition of new species
and strains from Torreón vicinity in Mexico (E. F. Legner and B. Villegas,
unpub. data). Extensive insecticide treatment during introduction, however,
precluded establishment in most areas. Some success was achieved outside the
principal grape production area near Redding, with the establishment of Apanteles spp. and Ametadoria spp. This insect is
now regarded a serious pest of commercial vineyards and backyard vines, as
well as in wild grapes, Vitis
californica Bentham. Apanteles harrisinae and A.
miscella were not
successfully established in the San Joaquin Valley (Flaherty et al. 1985).
Only a few parasitoid recoveries were made at release sites which may be
related to heavy spray pressure during the introduction period (E. F. Legner,
unpub. data). Samples of larvae taken from heavily infested and abandoned vineyards
in San Diego County showed only 13% parasitism, which is below the 42-62%
reported by Clausen in 1953-54 (Clausen 1961). There was also no evidence of
virus present. Clausen (1961) thought that the virus must be credited with
the major role in reducing grapeleaf skeletonizer populations to low levels
and exterminating many small infestations. Flaherty et al. (1985) considered
that at that time the virus was more widespread and had reduced grapeleaf
skeletonizer populations to levels that made it more manageable by the
parasitoids. This may account for the greater parasitism reported by Clausen
(1961) and that found by Flaherty et al. (1985). However, the present absence
of virus in abandoned vineyards in San Diego County and the absence of
observable grapeleaf skeletonizer in wild grapes is considered an enigma. The
grapeleaf skeletonizer has been known to show cyclic abundance, however, and
the surveys conducted in San Diego County could have been during one of the
cyclic outbreaks. Surveys by Legner (unpub. data) during other years have
shown this insect to be as rare as reported by Clausen earlier. Also,
widespread application of insecticides to vineyards in the south could be
responsible for minimizing natural enemy activity. In the San Joaquin Valley
the virus of grapeleaf skeletonizer is extremely virulent and has the
potential of becoming incorporated into an areawide biological control
effort, including wild grapes, backyard vines and commercial vineyards
(Flaherty et al. 1985). Pyralidae.--The grape leaffolder, Desmia
funeralis (Hübner), is a
pest of grapes in the central and southern San Joaquin Valley. The larvae
rolling and feeding on the leaves cause injury. Some feeding on fruit occurs
at high densities, but economic damage usually occurs only with massive, late
season infestations (Jensen & Flaherty 1981b). The larval parasitoid Bracon cushmani (Muesebeck) commonly attacks grape leaffolder.
Parasitism ranges from 30-40% and higher. Bracon
cushmani usually increases
in summer and frequently reduces the size of the second and third brood to
such small numbers that little increase in host populations is detectable
(Jensen & Flaherty 1981b). Sesiidae.--The
grape root borer, Vitacea polistiformis (Harris) is a
pest of grapes east of the Rocky Mountains. Larvae prune and girdle grape
roots by excavating irregular burrows (Jubb 1982). Saunders & All (1985)
showed an inverse correlation between the severity of V. polistiformis
and the activity of entomophilic rhabditoid nematodes in vineyard soils.
Laboratory and field bioassays determined the susceptibility of 1st instar
larvae to the nematode Steinernema
feltiae Filipjev, and the
insect nematode interaction was considered a type of natural control on
larvae. Augmentation of entomophilic rhabditoid nematodes during the critical
period of oviposition and eclosion was suggested as a technique for control. Curculionidae.--Adults of Naupactus
xanthographus (Germar)
consume grape buds and leaves in Chile (Gonzalez 1983). Damage also occurs when
feces adheres to foliage and fruit clusters. Combined damage by adult and
larval feeding on root-weakened vines. A complex of pathogens (bacteria,
fungi), nematodes and insects attack larvae and pupae in the soil. A nematode
of the family Rhabditidae parasitizes 4th-5th instars. The same nematode
attacks other Coleoptera and can be reared on wax moth larvae, Galleria melonella (L.). Gonzalez (1983) reported that larvae are
often attacked by nematodes that are transported in irrigation water, but the
degree of control was not evaluated. Of importance as a natural enemy is Platystasius sp (Fidiobia sp.). Up to 60% of the
egg masses under the bark can be attacked. Gonzalez (1983) reported that its
action in conjunction with the complex of other natural enemies is sufficient
to keep N. xanthographus below the
economic threshold. Otiorhynchus sulcatus
(F.), the black vine weevil, is important in horticultural crops in Europe,
the United States, Canada, Australia and New Zealand. Adults seriously damage
berry pedicels and cluster stems and larvae feed on roots in Europe and
central Washington (Bedding & Miller 1981). The application of aqueous
suspensions of infective juvenile Heterorhabditis
heliothidis (Khan, Brooks
& Hirschmann) to the soil resulted in up to 100% parasitism of larvae of O. sulcatus in potted grapes in nurseries. Pupae and newly
emerged adults were also parasitized. Steinernema
bibionis (Bovien) was found
less effective. Bostrichidae.--Medalgus confertus (LeConte), a branch
and twig borer, is found in California associated with many species of
cultivated and native trees and shrubs. In grapes both adult and larval
stages cause injury to grapevines (Joos 1981). Little is known about the
natural enemies of M. confertus, but a neuropteran
predator in the Rhaphidiidae, and two coleopterans in the families Carabidae
and Ostomidae may be very active. Recent studies have shown that the
entomophagous nematode, S. feltiae, can move through frass
tubes to infect larvae. Thripidae.--Several species of thrips, such as Frankliniella spp. and Drepanothrips
reuteri Uzel, can be
pestiferous on grapes worldwide (Flaherty & Wilson 1988). Jensen et al. (1981) report that little is known about their natural control
in California, however. Some studies in California citrus show that
phytoseiid mites Euseius tularensis Cugdon can control
the citrus thrips Scirtothrips
citri (Moulton). Schwartz
(1987) reported that Amblyseius
citri van der Merwe &
Ryke preyed on Scirtothrips aurantii Faure in South Africa.
Schwartz (1987) also found that Amblyseius
addoensis van der Merwe
& Ryke most likely preyed on Thrips
tabaci Lindemann in South
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