398 Invasive Stink Bugs and Related Species (Pentatomoidea)
in pheromone traps placed in the field have limited, thus far, the usefulness of this method for predicting
damage to a particular crop.
Vibrational pulses, also termed songs, are used by both sexes at medium range for calling (i.e., attract-
ing the opposite sex) and at short range for courtship of mates, repelling, and rivalry. These songs are
short in duration, lasting only a few hundred milliseconds to a second by males and several seconds in
the case of the female-repelling song (Čokl et al. 2000). Distinct songs by Nezara viridula have been
identified for location of females, courtship, a copulatory song, and a male rival song (Čokl et al. 2001).
Studies show that the songs are species-specific and the frequency ranges are highly appropriate for
transmission in the host plant (Kon et al. 1988, Čokl et al. 2000). N. viridula populations maintain simi-
lar temporal patterns and frequency characteristics in their songs despite collection of populations from
different continents (Čokl et al. 2000).
7.5 Current Impacts in Agriculture
- 5 .1 A s i a
Nezara viridula is a highly polyphagous species, attacking both monocot and dicots. Oho and Kiritani
(1960) listed as many as 145 plant species belonging to 32 families as its host plants. Todd (1989) describes
the N. viridula host range as “over 30 families of dicotyledonous plants and a number of monocots.” In
North America, 43 families with a total of 197 plant taxa (i.e., 158 identified to species and 39 identified
to genera) have been associated with N. viridula (see Section 7. 4. 5 and Tables 7. 4 and 7. 5). Taking
into consideration that the species can breed, or at least feed, during some stages of its development on
numerous cultivated and wild subspecies, cultivars or forms, it seems impossible to compile a compre-
hensive list of its host plants. However, it always is mentioned that the species demonstrates a strong
preference for leguminous plants (Table 7. 5; Todd and Herzog 1980, Todd 1989, Panizzi et al. 2000).
It often is mentioned that during the vegetative stages of host plants throughout the season, different
generations of Nezara viridula breed upon or utilize different plant species (Singh 1973). Most of the
damage comes from the feeding of nymphs on developing pods, seeds, or fruits and results in significant
reductions in yield, quality, and germination of seeds.
In Japan, Nezara viridula is a pest of rice, soybean, fruits, and many other agricultural crops. For some of
them (such as rice, soybean, and tomatoes), it is a major pest; for others, it is minor, one of a large complex
of heteropteran pests. This variable pest status is the reason why statistics estimating damage to agriculture
caused by this pest are lacking. Also, damage to rice caused by stink bugs is mostly not the yield loss but loss
of grain quality (i.e., pecky grains) as a result of feeding by the bugs. If pecky grains are present at a rate over
1/1000 grains, then the quality grade of rice goes down to second class with a substantial reduction in price.
The outbreaks of Nezara viridula in the 1950s in Miyazaki Prefecture (Kyushu) was induced by the
cultivation of early planted rice. The emergence of the first generation adults was synchronized with
the heading of early planted rice, which provided suitable food for the bugs. The following genera-
tions of the pest utilized middle-season and late-planted rice. Another factor that increased damage by
N. viridula was the cultivation of soybeans. Due to the overproduction of rice in Japan, the government
encouraged and subsidized farmers to plant alternative crops such as soybeans. The soybean cultivation
provided a good alternative host plant for the bug, and the pest actively utilized the crop particularly
when producing its third and/or fourth generations in late autumn.
Also starting from 1950s, temperatures (and particularly winter temperatures) in central Japan dem-
onstrated an increasing trend (Musolin 2007) and, as previously mentioned, milder overwintering
conditions are beneficial for building up populations of Nezara viridula. Thus, it seems likely that the
combination of three factors (i.e., cultivation of early-season rice, introduction of soybean, and increas-
ing winter temperatures) have encouraged expansion of N. viridula in Japan.
In general, since the 1950s, the composition of heteropteran pests of rice has changed in Japan from
relatively monophagous plant-sucking stink bugs with a univoltine seasonal cycle [e.g., Scotinophara
lurida Burmeister and Niphe elongata (Dallas) [as Lagynotomus elongatus (Dallas)]] to ear-sucking
stink bugs with wide host ranges and multivoltine seasonal cycles [e.g., Nezara viridula, Cletus punctiger