Stink Bug Damage in Relation to Soybean Phenology and Stink Bug Numbers'/
I. D. Teare and J. E. Funderburk2/
Southern green stink bug (SGSB) is the most important pentatomid pest of
soybean in the Americas. The host range is wide, but the pest prefers certain
plants, particularly some of the legumes (Todd and Herzog 1980). The life
history has been studied in many parts of the world. Harris and Todd (1980a,
b, c, d) present information on the species in the southern U.S. Five
generations are typical in the region (Todd and Herzog 1980). Adults
overwinter in above-ground habitats (Jones and Sullivan 1981), and several
wild and cultivated plants serve as primary hosts during the rest of the year
(Jones and Sullivan 1982). The relationship of SGSB to soybean has been
extensively studied. Reviews of the published information are contained in
Panizzi and Slansky (1985). The population dynamics of SGSB in relation to
soybean phenology are understood. Soybean phenological stages are according
to descriptions by Fehr and Caviness (1977). Adult SGSB exhibit distinct
preferences for soybean during the early reproductive podding stages. Adults
from other habitats move into the crop during this period of crop growth, with
peak oviposition occurring during R4 (Schumann and Todd 1982). An entire
generation of the pest then develops in the crop. The largest populations
occur from this generation which will be primarily late nymphal instars and
young adults during crop senescence (Schumann and Todd 1982, Menezes et al.
1985). Numerous control tactics have been developed for controlling the pest
in soybean. The most common practice is insecticidal control, but a cultural
control tactic also has been worked out (e.g., Newsom and Herzog 1977).
Numerous studies have been published relative to the effects of SGSB and
other stink bugs on soybean yield and/or seed quality. Todd and Turnipseed
(1974) measured % seed injury, seed yield, and seed size of soybean infested
with 3rd, 4th, and 5th instars and adults at 3, 6, and 9 weeks after crop
blooming. Only adults infested three weeks after bloom resulted in signifi-
cant yield reductions, but seed damage occurred for most treatments. Seed
size was not affected. Yeargan (1977) caged the green stink bug, Acrosternum
hilare (Say), on soybean maintaining the same specified numbers at two
densities from early pod development to harvest maturity. Significant effects
on yield and seed quality were noted. McPherson et al. (1979) maintained
three densities of SGSB and other stink bugs on soybean in cages during
pod-filling stages, with seed yield and quality influences detected. Todd and
Mullinnix (1985) put 5th-instar nymphs in cages for 14-21 days to investigate
the interactive effects of SGSB and velvetbean caterpillar, noting yield and
seed-quality effects. Thomas et al. (1974) put adult SGSB on caged soybean
during several reproductive soybean growth stages. The first infestation
period most closely represented the actual dynamics of the pest in soybean,
and this was the only time that significant effects on yield and seed quality
were noted. The effects of the initial adult populations and subsequent
developing populations were not separated.
1/Contribution from the Inst. of Food and Agric. Sci. Florida Exp. Stn., Univ.
of Florida, and the North Florida Res. and Educ. Ctr., Quincy, FL 32351.
Research Report NF 87-4.
2/Research Scholar/Scientist of Agronomy and Assistant Professor of Ento-
mology, respectively, Univ. of Florida.
Todd and Turnipseed (1974) quantified significant reductions in germin-
ation, emergence, and seedling survival by all degrees of SGSB damage. Jensen
and Newsom (1972) showed that the amount and location of stink bug damage to
soybean seeds affected seed emergence and subsequent yield. Numerous other
workers have reported similar findings. The chemical composition of the seed
also is altered (e.g.; Todd and Turnipseed 1974, Todd 1976).
Although numerous studies have been conducted concerning the effects of
stink bugs, especially SGSB, on seed yield and quality, none have accurately
reflected the actual ecological relationship between the crop and the pest.
The effects of stink bugs on soybean parameters other than seed yield and
quality have not been studied. Therefore, we propose research to rectify
these informational shortfalls.
The objectives of this research is to quantify the effects of SGSB stress
on soybean growth, yield, and seed quality according to plant/insect dynamics
and to develop economic injury levels for southern green stink bug on soybean
according to plant/insect dynamics.
Materials and Methods
This study was conducted at the North Florida Research and Education
Center at Quincy, Florida (1986) on an Orangeburg loamy sand clayeyy, kaolini-
tic, thermic, Typic Paleudult). The experimental site was treated with .56
Kg/ha lb ai/A Treflan 4E and .42 Kg/ha Sencor 50WP herbicides (5-23-86). The
field was rough cut once before the preplant herbicide was applied then smooth
harrowed twice to incorporate the herbicide. On 5-27-86 Braxton soybean were
planted. The field was later cultivated twice with a 2-row rolling culti-
The experimental design was a randomized complete block with rows planted
0.76 m apart, and seeds planted 8 per 0.30 m of row. At early stage R4 of
soybean development, 64-0.91 x 1.22 x 1.22 m insect cages were randomly placed
in the plots. The cages were wood framed and wire (screen) mesh, entry ports
on either side were covered with 0.30 m of surgical cotton tubing. This
allowed entry into the cage to collect dropped leaves, petioles, pods and dead
stink bugs but contained the live stink bugs. Cages were firmly anchored and
their bases sealed with soil. Adjacent soXbean plants were left undisturbed.
The cage reduced PAR from 1.700 pmol m2 s to 1.1 imol m2 s- on 8-19-86 at
11:20 EDST or approximately 35%.
SGSB adults were introduced into the cages during early R4 at four densi-
ties. These SGSB were collected as 5th instars and young adults from other
hosts in the ecosystem, primarily corn, seven days prior to infestation. They
were kept in the insectary where they were fed corn and allowed to mate. This
procedure simulates actual conditions that occur in soybean where feral adults
infest the crop at the appropriate time from other habitats in the ecosystem
(Schumann and Todd 1982). Previous food source has been shown to affect SGSB
adult biology (Kester and Smith 1984). On July 26, 1986 the 16 cages in Rep 1
were infested with stink bug numbers of 0, 2, 6, and 12 per 1.22 m of soybean
row sex ratio 1:1. Reps 2, 3, and 4 were infested in the same manner on July
29, Aug. 4 & 5, respectively. The cages were checked twice weekly for stink
bug death, leaf and petiole drop, and cage damage. Dead stink bugs were
replaced for two weeks after initial infestation.
The first harvest was taken August 22, 1986. Sixteen cages were
harvested, one from each stink bug number in each replication. Stink bug
number, sex and stink bug stage of development were recorded. The plants were
cut at ground level, soybean stage of development recorded and then the
foliage was partitioned into leaves, petioles, stem and pods, dried at 700 C
and weights recorded when weight became constant. The second harvest was
taken on September 12, when 16 additional cages were harvested and processed
in the same manner. Harvest at maturity was based upon the appearance of the
plants in relation to leaf drop. Maturity date and living and dead stink bug
numbers were recorded and soybean harvested and processed as before.
The analyses of seed damage and vigor is in the processing stages. Seed
damage is being determined based on Jensen and Newsom's work (1971).
The soybean seeds are being separated into five categories, determined by
visual damage. Group one seeds have no visual damage. Group two are slightly
damaged seeds with a puncture wound. No shriveling of seed coat, yet some
discoloration. Approximately 1/3 of the seed coat damaged. Group three
contains the seeds with about 2/3 of the seed coat shriveled and discolored.
Group four contains the seed with total damage, the entire seed coat shriveled
and discolored. Group five consists of seed which are damaged, however, not
by stink bugs. These seed contain earworm damage or fungal disease, i.e.,
purple or brown stain.
The slightly damaged seeds will be separated further into groups based on
the location of the sting on the seed. This is to determine if the stink bug
has a preference as to where they sting the seed. The four categories are the
embryo sting, hypocotyl sting, top of the hypocotyl, and the hilum sting.
Once the seeds have been separated in the various categories, a
germination technique will be applied. However, this technique has not been
There will also be a viability test using 2, 3, and 5 Triphenzltetrazolium
chloride. This procedure has been outlined by Delouche et al. (1962).
Results and Discussion
A preliminary study was conducted by the authors in 1986 to develop
appropriate methodology for studying the effects of SGSB on physiology and
morphology of soybean in relation to time. Early populations of migrating
adults from 0 to 4X the current Florida threshold did not affect stem weight,
petiole weight, leaf weight, pod weight, seed weight, or harvest maturity
(Table 1). Populations of the subsequent generation greatly affected soybean
morphology (Table 2).
Table 1. Effects of early adult southern green stink bug populations at four
densities on stem weight, petiole weight, leaf weight, pod weight,
seed weight, and maturity date of soybean at harvest maturity. (No
numbers in the same vertical column are significantly different at P
Southern Green Stink Stem Petiole Leaf Pod Seed Maturity
Bug Density Wt. Wt. Wt. Wt. Wt. (DAP)*
0 123.3 5.9 2.8 48.6 155.1 143.4
2 120.1 8.1 1.8 57.8 151.3 143.7
6 138.9 5.8 1.4 56.8 176.0 144.8
12 122.0 12.1 4.2 53.2 169.7 145.6
*DAP = Days after planting soybean
Table 2. Mathematical relationships between subsequent southern green stink
bug numbers of the generation developing from eggs laid R4-R5 (X)
and soybean morphological parameters and maturity date (Y).
Soybean Parameter (Y) Function R2
Stem weight(g) at harvest Y = 124.1 + 0.205X 0.22
Petiole weight (g) at harvest Y = 6.56 + 0.230X 0.77
Pod weight(g)* at harvest No significant function
Leaf weight(g) at harvest Y = 0.50 + 0.292X 0.92
Seed weight(g) at harvest Y = 161.5 0.594X 0.67
Maturity date** Y = 8.19 + 0.243X 0.00079X2 0.41
*Pod weight after seed removal
The subsequent SGSB was positively related to stem weight, petiole weight,
leaf weight, and harvest maturity were positively related to SGSB numbers
(Fig. 1, 2, 3, 4). Seed weight was negatively related to subsequent SGSB
numbers (Fig. 5), while pod weight (seeds removed) was unaffected (Fig. 6).
Leaf drop in relation to time is shown in figure 7, where stink bugs were
excluded from the soybean. The curve shows the greatest leaf drop on October
3. Figure 8 shows leaf drop in relation to time and a high stink bug number
at harvest. On October 3 when you expect a large number of leaves to drop
only small number of leaves were dropping. Stink bug numbers in relation to
shown for that caged area in figure 9.
119 live adult stink bugs in the cage.
days were 116.
At harvest on November 3 there were
Stink bug deaths for the previous 10
This information will allow for calculating the influences of SGSB on
carbohydrate partitioning. The immediate importance of this information to
management of the pest is obvious, but numerous other parameters, both
morphological and physiological, need to be measured. Additional years of
data also are vitally important.
T 128 + 0.219X
Y = 5.29 + 0.324X
X = 5S.O
0 30 s60 0 (2 150
Stinkbug No. at Harvest.
Y = 146 + 0.431X 0.00225X2
Y 173 0.913X
No significant function
0 30 60 90 120 M0
Stinkbug No. at Harvest
Figure 1. Morphological soybean changes in relation to stink bug number
at harvest, 1986.
T Y -1.22 0.390X
B 1 15 L 22 Z6 12 13 17 22 24 28 31
AUG. SEPT. OCT.
Figure 2. Leaf drop in relation to time for cage A where 6 southern green stink bugs (SGSB)
infested the cage, 119 stink bugs were found alive at harvest and 116 were found
dead 10 days before harvest vs cage B where 0 stink bugs infested the cage, 1986.
' ` ~ ' ` -I-
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