Phenology of emergence from artificial overwintering shelters by some predatory arthropods common in pear orchards of the Pacific Northwest

2004·4.5 MB·English

by  David R Horton

J. Entomol. Soc. Brit.Columbia 101,Dechmber2004 101
Phenology of emergence from artificial overwintering
shelters by some predatory arthropods common
in pear orchards ofthe Pacific Northwest
DAVID HORTON^
R.
ABSTRACT
The phenology ofemergence from artificial overwintering shelters that had been placed
in pear orchards located near Yakima, Washington, was determined for the green lace-
wing Chrysopa nigricornis Burmeister, the predatory mirid Deraeocoris brevis (Uhler),
and the brown lacewing Hemerobius ovalis Carpenter. Cumulative emergence from
shelters was determined in 2001 and 2002 on both a calendar-date and degree-day basis.
Similar data for a majorpear pest, pear psylla, Cacopsyllapyricola (Forster), were also
collected for these same shelters. Pear psylla and H. ovalis emerged earliest, both taxa
completing emergence by early March (120 degree-days accumulated from early Janu-
ary). Deraeocoris brevis emerged beginning in late February and finished emergence
by early April (150 degree-days for 90% emergence). Chrysopa nigricornis emerged
considerably laterthan the other species, and completed emergence by late May orearly
June. Calendar-date emergence is also shown for spiders (Araneae) and Anthocoridae
(Heteroptera), which occurred at lower numbers in the shelters. The anthocorids, Orius
tristicolorWhite andthree species ofAnthocoris, emerged from shelters in February and
March, while spiders emergedovera long interval between March and May.
KeyWords: overwintering, spring emergence, biological control, pearpsylla, green
lacewings, brown lacewings, predatory Heteroptera
Many species of predatory arthropods pause, overwintering biology, and post-
overwinter in pear orchards of the Pacific diapause development. Here, I describe
Northwest (Horton et al. 2001, 2002), and phenology ofemergence from overwinter-
it is likely that some ofthese taxa provide ing quarters for several predatory species
biological control of orchard pests in known to overwinter in orchards (Horton
spring. As broad-spectrum insecticides are et al. 2002). Late-winter and early-spring
used less extensively and selective controls control of pear pests such as pear psylla,
such as mating disruption are put into Cacopsyllapyricola (Forster), is important
place, pear growers in the Pacific North- for season-long management (Westigard
west may benefit from increased levels of and Zwick 1972), and results reported here
biological control (Knight 1994; Gut and should assist growers in better predicting
Brunner 1998). Yet, for many predatory when certain predators are likely to be ac-
taxa, much remains unknown about certain tive in theirorchards.
life history characteristics, including dia-
MATERIALS AND METHODS
Tree bands of corrugated cardboard been used to monitor a variety ofoverwin-
were used to provide overwintering shel- tering predatory arthropods, including
ters for arthropods. Cardboard bands have Neuroptera (New 1967; Mizell and Schiff-
^USDA-ARS,5230KonnowacPassRd.,Wapato,WA, UnitedStates98951
102 J.Entomol.Soc.Brit.Columbia 101,December2004
hauer 1987; Horton et al. 2002), spiders identified as Hemerobiiis ovalis Carpenter
(Horton et al 2001), and Heteroptera (Fye (Kevan and Klimaszewski 1987). Voucher
1985; Horton et al 2002), all taxa that specimens of C. nigricornis and H. ovalis
were monitored in the present study. Each are inthe collection ofthe author.
band was 7.6 cm wide and long enough to Temperature in the shed was recorded
completely encircle the trunk of the pear at hourly intervals using a Hobo data log-
m
tree 0.2 to 0.3 above the orchard floor. ger (Onset Computer Corporation, Bourne,
Corrugations in the cardboard were ca. 4 x MA) placed in one of the containers. In
5 mm, which is large enough to allow ar- the first year of the study, a second Hobo
thropods the size of adult Neuroptera to recorder was placed in a pear orchard lo-
m
colonize the corrugations. Ten trees were cated 500 south of the shed, to deter-
banded in each of 19 and 24 orchards in mine whether temperatures in the shed
October or November of 2000 and 2001, were similar to those occurring in the
respectively. Orchards were primarily neighboring orchard. The Hobo unit was
'Bartlett' and 'D'Anjou' varieties, ofvari- placed in a white, ventilated wooden box
ous ages. The orchards extended from the (15 X 30 X 30 cm) at 1.5 m above ground.
eastern Yakima Valley (Zillah and Parker, Cumulative percent emergence from
Yakima County, WA) to the western part shelters was expressed as a function of
of the valley (Yakima, Cowiche, and Tie- calendar-date and as a function ofaccumu-
ton, Yakima County, WA). Pest control lated degree-days. Emergence curves were
practices included a range ofmanagement developed for the 3 predatory taxa most
programs from conventional insecticidal to abundant in the bands, which were two
organic. lacewings, C. nigricornis and H. ovalis,
The bands were removed from the field and a mirid bug, Deraeocoris brevis
in the first week ofJanuary 2001 and 2002 (Uhler). One pest species, pearpsylla, was
andplaced in white plastic boxes (100 x 40 also monitored. For some less common
X 24 cm). The boxes had organdy screen- taxa (spiders, Anthocoridae), emergence
ing on the top and four sides to allow air from bands was summarized for two-week
circulation. A separate containerwas used intervals and presented in tabular form.
for each orchard. Bands and containers "Emergence" used throughout the manu-
were then placed in a large shed enclosed script refers to the dates that the arthropods
on 3 sides by wire screening, located 15 were aspirated from the walls of the con-
km southeast of Yakima, WA. The shed tainer. Certain arthropods (e.g., jumping
was not heated or lighted. spiders [Sahicidae]) may have moved in
Containers were checked every 3 or 4 and out of the corrugations, and for these
days beginning in earlyJanuary and ending taxa it is not clear that "emergence", as
in early June ofboth years. The lid, sides, used here, necessarily reflects what occurs
and floor ofeach container were examined in the field.
for pear psylla, predatory insects, and spi- Data from the Hobo recorders were
ders. Arthropods were counted and aspi- used to calculate degree-days by means of
rated into vials. Specimens other than a program available on the Oregon State
Chrysopidae and Hemerobiidae were dis- University web-site (Coop 1999). The
carded after having been counted. The calculations were done using the single
lacewings were taken to the laboratory for sine curve method and a lower threshold of
further examination. Chrysopids were 5 °C. Accumulations both years began
identified as Chrysopa nigricornis Bur- when the bands were placed in the
meister using the key in Penny et al. screened shed (8 January 2001 and 10
(2000). A subsample (n = 42) ofHemero- January 2002).
biidae was examined; all specimens were
J. Entomol. Soc. Brit.Columbia 101,December2004 103
RESULTS
Temperatures were higher in 2002 than early April in 2001 (Fig. 2). Chrysopa
2001 (Fig. 1). In 2001, when both the nigricornis was considerably later in emer-
screened shed and the neighboring orchard gence than the other two predatory taxa,
were monitored, temperatures were higher and completed emergence by the middle of
in the shed than in the orchard. Thus, data May in 2002 and by early June in 2001.
presented below expressing emergence as Emergence in 2001 did not begin until
a function ofcalendar-date probably show early May; by this time in 2002, C. nigri-
emergence from bands to have occurred cornis had achieved 50% emergence.
earlier than that taking place naturally in Emergence from shelters was also ex-
the neighboring orchard. pressed as a function ofcumulative degree-
Pear psylla were extremely abundant in days (Fig. 3). Full emergence from shel-
the bands both years (Table 1). Of the ters by pear psylla required few heat units.
natural enemies, C. nigricornis, D. brevis, Hemerobius ovalis had completed 90% of
andH. ovalis occurred at the highest densi- emergence by 73 and 111 cumulative de-
ties. Less common were spiders and An- gree-days in 2001 and 2002, respectively.
thocoridae {Orius tristicolor (White), An- Curves for D. brevis were very similar the
thocoris spp.). Anthocoris spp. included^. two years, and this species required about
antevolens White, A. whitei Reuter, andA. 150 degree-days to complete 90% emer-
tomentosus Pericart. Species' identifica- gence from shelters (Fig. 3). Chrysopa
tions were not made for all samples, so I nigricornis began emerging from bands at
combined the three species as Anthocoris about 400 degree-days, andrequired 600 to
spp. 730 degree-days to complete 90% emer-
Pear psylla and H. ovalis began emerg- gence. Fifty percent emergence for C.
ing from bands by early February in both nigricornis required 500 and 520 cumula-
years of the study (Fig. 2). Psylla had tive degree-days in 2001 and 2002, respec-
completed emergence by early March tively. Curves for C. nigricornis were very
(2001) and early February (2002); the dif- similar in the two years until at the end of
ference in calendar dates the two years the emergence period, when emergence
reflects the warmer temperatures in 2002 from bands in 2001 was slower than in
than 2001 (Fig. 1). Hemerobins ovalis had 2002 (Fig. 3).
finished emergence by early March. As Spiders emerged over a fairly broad
with pear psylla, emergence occurred ear- interval (Table 2), probably because this
lier in 2002 than 2001. Deraeocoris brevis taxon comprised a mix of species. The
began appearing in containers in late Feb- anthocorids emerged in late February and
ruary both years and had finished emer- early March (Table 2).
gence by the middle ofMarch in 2002 and
1 Feb 1 Mar 1 April 1 May 1 June
Figure 1. Accumulated degree-days within shed, 2001 (closed circles) and 2002 (closed trian-
gles), andin an orchardneighboringthe shed, 2001 (open circles).
104 J.Entomol. Soc.Brit.Columbia 101,December2004
Table 1.
Cumulative numbers of common arthropods emerging from cardboard bands in Jan-June of
2001 (N = 190) and2002 (N = 240).
2001 2002
Cacopsyllapyricola (Homoptera: Psyllidae) 4638 4778
Chry^sopa nigricornis (Neuroptera: Chrysopidae) 237 163
Deraeocoris brevis (Heteroptera: Miridae) 159 235
Hemerobius ovalis (Neuroptera: Hemerobiidae) 136 111
Spiders (Araneae) 42 104
Orins tristicolor(Heteroptera: Anthocoridae) 6 69
Anthocoris spp. (Heteroptera: Anthocoridae) 8 66
# Pearpsylla
V
100 W.ovafis
A
c.nigricornis
O D.brevis
80
60
8 40
P
20
0
E
-c*-*
1 Feb. 1 Mar. 1 April 1 May 1 June
? 2002
100
£ 80 W o A
o
o
o
60 -
40 voo
20
o
1 Feb. 1 Mar. 1 April 1 May 1 June
Figure 2. Cumulative emergence from bands in 2001 and 2002 by pear psylla (solid circles),
Hemerobius ovalis (inverted triangles),Deraeocoris brevis (open circles), and Chrysopa nigri-
cornis(triangles) versus calendardate (cf. Table 1). Dotted lines depict 50 and 90% cumulative
emergence.
J. Entomol. Soc. Brit.Columbia 101,December2004 105
2001
100 iOOODOO 'OCi O O O 2 QOO
A
80
0°
60
40
• Pearpsylta
20 •O A HC..onviaglriiscomis
O
D.brevis
0 ^/m^i522i^AAAAA
200 400 600 800 1000
2002
100
80 • V''- A
60 • V
A
40
A
20
A
W
0 AA A^
0 200 400 600 800 1000
Cumulative degree-days
Figure 3. Cumulative emergence from bands in 2001 and 2002 by pear psylla (solid circles),
Hemerobius ovalis (inverted triangles), Deraeocoris brevis (open circles), and Chrysopa nigri-
comis (triangles) versus accumulated degree-days (cf. Table 1). Dotted lines depict 50 and
90% cumulative emergence.
Table 2.
Numbers ofspiders, Orius tristicolor andAnthocoris spp. {A. antevolens, A. whitei, A. tomen-
tosus) emerging frombands in 2001 and 2002 versus calendardate.
2001 2002
Spiders Spiders Orius tristicolor Anthocoris spp.
1-15 Jan 0 1 3 1
16-31 Jan 0 10 19 7
1-15 Feb 0 7 35 16
16-28 Feb 5 7 10 22
1-15 Mar 8 18 2 9
16-31 Mar 8 25 0 7
1-15 Apr 9 23 0 4
16-30Apr 6 10 0 0
1-15 May 5 3 0 0
16-31 May 1 0 0 0
106 J.Entomol. Soc.Brit.Columbia 101,December2004
DISCUSSION
With reduced use of broad-spectrum wing is a common inhabitant ofdeciduous
insecticides and increased use of selective fruit andnut orchards (Grasswitz and Burts
controls such as mating disruption or nar- 1995; Szentkiralyi 2001), apparently as a
row-spectrum insecticides, fruit growers in generalist predator of soft-bodied insects
the Pacific Northwest may experience in- such as aphids, mealybugs, and psyllids
creased levels ofbiological control in their (Toschi 1965; Grasswitz andBurts 1995); I
orchards (Westigard et al. 1968; Knight have reared C. nigricornis to the adult
1994). Results reported here and else- stage on a diet ofnymphs and eggs ofpear
where (Horton et al. 2001, 2002) indicate psylla (DRH, unpublished data). Chrysopa
that a large diversity of predatory arthro- nigricornis has a facultative diapause con-
pods may overwinter in pear orchards. trolled by photoperiod, and overwinters as
Horton et al. (2001, 2002) described sea- a third instar within the cocoon (Tauber
sonalphenology ofautumn entry into over- and Tauber 1972). The species emerged
wintering shelters by natural enemies in from overwintering shelters considerably
pear orchards. Practical aims were to tell later in the season than the other predator
growers whether late-season insecticide orpest species monitored here, and had not
applications, if made, would occur while completed emergence until well into May
predatory arthropods were still active in both years (Fig. 2). Mizell and Schiff-
the orchard. In the present study, I exam- hauer (1987) showed that C. nigricornis
ined phenology of emergence from over- emerged from overwintering shelters
wintering quarters. Calendar-day or de- placed in pecan orchards ofGeorgia begin-
gree-day models for use in predicting ning in late March and early April, much
emergence from overwintering sites in later than spiders and a coccinellid beetle
deciduous fruit or nut orchards in North common inthose orchards.
America havebeen developed forboth pest Thebrown lacewingH. ovalis, likepear
(Bergh and Judd 1993) and predator psylla, began emerging from bands after
(Felland et al. 1995; Mizell and Schiff- only minimal accumulation of heat units
hauer 1987) species. (Fig. 3). Species of Hemerobiidae often
Of the four most common taxa that show activity or development at relatively
emerged from the bands, pear psylla was cool temperatures (Neuenschwander 1976;
the most abundant (Table 1). This insect is Canard and Volkovich 2001), so their
among the most damaging arthropod pests emergence in late winter is not unexpected.
of pears in North America and Europe Biology ofHemerobitis species, including
(Westigard and Zwick 1972; Solomon et diapause and overwintering, is poorly de-
al. 1989). Pear psylla overwinters in the scribed. Within the Hemerobiidae, all
adult stage as a distinct morphological stages from egg to adult have been re-
phenotype, the winterform, which began corded to overwinter (Canard and Volk-
appearing in pear orchards of the study ovich 2001). In the present study, brown
area in early September. The species is lacewings emerged from the bands as
active at cool temperatures, and can be adults, and I assume that they overwintered
seen moving about on the pear tree in mid- in this stage. Adults of several
winter on sunny days. Pear psylla began Hemerobins species, including H. ovalis,
emerging from the bands after only mini- have been collected in mid-winter in areas
mal accumulation of heat units (Fig. 3). of the Pacific northwest (Foster 1942;
Egg-laying in the study area commences Kevan and Klimaszewski 1987), which is
by March (Horton 1999). additional evidence that this species over-
A green lacewing, C. nigricornis, was winters in the adult stage. The role of
also abundant both years in the bands (see brown lacewings in orchards has not been
also Horton et al. 2002). This green lace- systematically studied, despite their fairly
J. Entomol. Soc. Brit.Columbia 101,December2004 107
regular appearance in temperate zone or- chards requires improved understanding of
chards (Szentkiralyi 2001). McMullen and natural enemy biology, including overwin-
Jong (1967) reported that H. pacificus tering biology. Horton and Lewis (2000)
Banks preyed upon eggs and nymphs of described use of natural habitats and or-
pear psylla in Canadian pear orchards, chards for overwintering by various spe-
while Nickel et al. (1965) stated that H. cies ofpredatory arthropods, while Horton
angustus Banks provided biological con- et al. (2001, 2002) described late-season
trol ofpsylla in Californiapearorchards. phenology of predators entering overwin-
Deraeocoris brevis has a facultative tering shelters. By knowing when preda-
diapause controlled by photoperiod, over- tors emerge from overwintering quarters,
wintering in the adult stage (Horton et al. growers would have a better idea about the
1998). This species emerged from bands potential for biological control early in the
beginning in late February or early March, season, a critical time for managing pests
and had completed emergence by mid- to such as pear psylla. Results reported here
late-March. Deraeocoris brevis preys ex- suggest that at least one known important
tensively on soft-bodied arthropods such as predator ofpear psylla, D. brevis, emerged
aphids and psyllids (McMullen and Jong from shelters early enough in late winter
1967; Messing and AliNiazee 1985) and that it could be active in pear orchards at
occupies a variety of habitats including the same time that overwintered pear
pear and apple orchards (Horton and Lewis psylla would be depositing substantial
2000). When pear psylla is at high densi- numbers of eggs (March and April). The
ties in pear orchards, this predator may be data also suggest, however, that D. brevis
among the most abundant of natural ene- and several other taxa (//. ovalis, O. tristi-
mies in the orchard (Westigard et al. color, Anthocoris spp.) could be active in
1968). McMullen and Jong (1967) stated Pacific Northwest orchards at the time of
thatD. brevis is second in importance only the earliest insecticide sprays. Thus, it
to species of Anthocoris as a predator of seems possible that these predators could
pear psylla in pear orchards of the Pacific be exposed to those early-season pest con-
northwest. trol practices.
Maximal use of natural enemies in or-
ACKNOWLEDGEMENTS
I thank Deb Broers, Merilee Bayer, and a previous version of this manuscript are
Dan Hallauer for assistance. Taxonomic appreciated. This research was partially
help was provided by Tamera Lewis and supported by the Winter Pear Control
Gene Miliczky. The comments of Rick Committee.
Hilton, Alan Knight, and Pete Landolt on
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