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BIOLOGICAL CONTROL OF ARTHROPODS IN
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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 which 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 which 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 that "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
which 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 is 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.
Injury is caused by the larvae rolling and feeding on the leaves. 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 roots weaken 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
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