Insects already introduced to North America
The genus Lipara Meigen is restricted to the Palaearctic region, and all nine presently recognized species use P. australis as their sole host plant. The European species L. lucens, L. rufitarsis, L. similis, and L. pullitarsis cause more or less distinct apical shoot galls, in which a single mature larva overwinters. All four species are widely distributed through Europe with variable but usually low (5-10%) attack rates.
Sabrosky (1958) records 1931 as the first North American record of L. lucens, based on material from Connecticut. The same author reports intercepting L. similis in New York in a shipment from the Netherlands where dry Phragmites stems were used as packaging materials. Use of Phragmites as packaging material may be a major mode of introduction for many other insects that overwinter in dry stems of this species. Recent regional surveys in the northeast United States reveal a widespread distribution and high abundance of L. rufitarsis, L. similis, and L. pullitarsis. However, L. lucens has not been found after the initial record in 1931 and may not be established in North America. Attack rates in the northeastern United States, particularly of L. similis, can approach 80%.
Lipara species can be best distinguished using criteria of gall morphology
and larval overwintering habit. Attack by L. lucens causes stunting of
10-13 internodes and larvae penetrate the growing point to feed in a gall
chamber. Attack by L. rufitarsis causes stunting of only 5-6 internodes
with larvae also penetrating the growing point. Attack by L. pullitarsis
causes stunting of apical internodes and gall formation similar to L.
rufitarsis, but larvae overwinter above
the growing point. Attack by L. similis causes only slight alterations of
Lasioptera hungarica Möhn (Diptera: Cecidomyiidae)
Lasioptera hungarica is a univoltine gall midge with P. australis as the only recorded host plant. The species appears to be more common in eastern and southern Europe. Shoots infested by L. hungarica show no obvious signs of damage; however, they often break in strong winds at the site of attack, suggesting a weakening of stem tissues. Larvae overwinter in the stem, and 30-300 yellow-orange larvae can often be found in a single internode. The species is easily identified by its association with a black fungal mycelium (genus Sporothrix) that fills the internode.
Oviposition by females also infects the stem with fungal spores providing food for the developing larvae. Lipara hungarica was recognized in North America in 1999 but the species is already widespread throughout the Northeast.
Marchal (Homoptera: Pseudococcidae)
European insects with potential as biological control agents
Archanara geminipuncta (Haworth) (Lepidoptera: Noctuidae)
This shoot-boring moth has been extensively researched in Europe because of its damage to reed beds. Larvae mine the shoots in spring and early summer, adults fly in the summer and eggs overwinter. Mined portions of shoots and the growing point wilt after attack.
A single larva needs several shoots to complete development, and attack rates of
over 50% of stems are common. Attack by this shoot-boring moth can reduce shoot
height by 50-60% and result in significant reed die-back. There are 2 “sister”
species of A. geminipuncta (A. neurica, A. dissoluta) with
very similar life-histories that are also under study in Europe.
Phragmataecia castaneae (Hübner) (Lepidoptera, Cossidae)
This large moth needs two years to complete its development, which occurs at the base of the shoot and in the rhizomes. Moths fly in summer and females lay 200-400 eggs. Larvae may move from shoot to shoot as they look for new food during their development. Larvae can be found in both dry reed stands and those that are permanently flooded.
Chilo phragmitella (Hübner) (Lepidoptera: Pyralidae)
Like P. castaneae, this species mines shoots and roots of Phragmites. Larvae are active in the summer; older larvae mine deeper parts of the rhizome and are difficult to detect. Infested shoots remain small and wilt.
Schoenobius gigantella (Denis & Schiffermüller) (Lepidoptera: Pyralidae)
Larvae of this moth mine shoots of flooded Phragmites below the water level, causing considerable damage. Attacked shoots wilt and break apart. Little is known about the life history of the species, but it is assumed that larvae need two years to complete development. Adults fly in the summer.
Platycephala planifrons (Fabricius) (Diptera:Chloropidae)
Platycephala planifrons attacks Phragmites shoots early in the year leading to severe stunting of attacked stems by killing the growing point. Platycephala planifrons was one of the most damaging species found during surveys in Europe. Attack can cause biomass reductions of >50%. Females fly in the summer and are long lived. Eggs are laid in late summer. Larvae hatch in late summer, feed for a limited period and overwinter.