|Country or region name
|| Ophraella communa
|English common name
|| ragweed beetle
|Substantially same species (synonym)
|Year of invasion or detection
|| North America
|Situation of establishment
|| Category 4: Settled after 1951, but not distributed all over the
|Expansion of distribution area
| This insect was firstly found in Chiba and several cities around
the Tokyo Bay in 1996 (Takizawa et al., 1999) and Osaka Prefecture in 1997
(Ichikawa et al., 1998). It expanded the distribution from Akita and Iwate
Prefectures to Kagoshima Prefecture including 39 prefectures until the
end of 2001 (Moriya and Shiyake, 2001; Moriya et al., 2002).
This beetle was firstly found in the area around the Tokyo Bay in 1996
and expanded its distribution almost all over the Kanto district in 1997;
its speed of expansion was 120 km in this year (Takizawa et al., 1999).
From the distribution records by Moriya and Shiyake (2001), an average
speed of expansion is estimated at over 100 km/year until 1999.
| The main host plant, ragweed Ambrosia artemisiifolia, produces serious allergenic pollen. In Japan, this insect often causes
severe damage to the ragweeds, and sometimes kills the plants before their
flowering. Thus, this insect may be a natural biocontrol agent against
the ragweed. However, its ecological impact on the ragweed has not been
| The larvae and adults of this beetle could complete the life span
by feeding on several cultivars of sunflower Helianthus annus, although the sunflower was less suitable as host than the ragweed Ambrosia artemisiifolia (Palmer and Goeden, 1991; Emura, 2000). In August and September, the insects
have sometimes caused damage to sunflowers, especially to dwarf cultivars,
sown in summer (Emura, 2000).
| In the laboratory, newly-emerging adults live long, a mean longevity
being over 60 days (Tanaka, unpublished). The females reproduce after several
days of a preovipositional period, e.g. 4 to 5 days at 25 C. The mean fecundity
exceeds 1000 eggs per female (Tanaka, unpublished), although the overwintered
females produce fewer eggs, 361 on an average (Emura, 1999). Emura (1999)
estimates that this insect has four or five generations in a year in Kanto
district, based on the effective accumulative temperature. However, it
is likely that the insect has three or four generations estimated by its
photoperiodic response and longevity (see [Growth] section).
| A life cycle of this species in Kanto district is estimated as follows.
Overwintered adults occur to reproduce on young shoots of the ragweed in
mid-April to early May. Adults of the first, second and third generations
occur in June, July and August, respectively. A short day-length induces
the reproductive diapause of the adults; a critical photoperiod is around
14 hr corresponding to early September (Watanabe, 2000). The fourth generation
adults may emerge in September. The adults can live long and the latter
generations overlap each other. Hence, a part of third generation adults
may enter diapause. The adults disappear in October to November probably
to overwinter. To complete a generation of this insect, the developmental
zero and the effective accumulative temperature were estimated at 13.1
C and 303 day-degree, respectively (Emura, 1999). In Japan, effective natural
enemies have not been found, although the pupae and adults were infected
with a fungus Beauveria bassiana and the eggs, larvae or adults were attacked by several predators, ladybird
larvae and adults Harmonia axyridis, green lacewing larvae, mantid nymphs and adults, stinkbug adults Piocoris varius and spider nymphs Agelena opulenta (Moriya et al., 2002). A parasitoid fly Chaetonodexodes vanderwulpi was found from the prepupae in California (Goeden and Ricker, 1985). In
Japan, however, no parasitoids have not recorded.
|Writer's name and affiliation
| © Written by Tanaka, K. National Institute for Agro-Environmental
Sciences. (updated on 30, Oct., 2003)