THE GREENHOUSE LEAF-TYER, PHLYCTAENIA RUBI- 
GALIS (GUENEE) 1 
By C. A. Weigel, Associate Entomologist , and B. M. Broadbent, Junior Entomo¬ 
logist , Fruit Insect Investigations , Bureau of Entomology; systematic description 
by August Busck, Associate Entomologist , Bureau of Entomology , and Carl 
Heinrich, Associate Entomologist , Federal Horticultural Board, United States 
Department of Agriculture 
INTRODUCTION 
The larvae of a small moth known 
as the greenhouse leaf-tyer, 2 Phlyctaenia 
rubigalis (Guen6e), 3 may be classed 
among the more important and de¬ 
structive enemies of chrysanthemum, 
cineraria, snapdragon, and a long list 
of other ornamental and greenhouse 
plants. According to recent authori¬ 
tative reports received by the Bureau 
of Entomology, this pest has, in several 
instances, occasioned complete de¬ 
struction of the plants attacked. The 
need for more complete information 
regarding its life history and control 
under greenhouse conditions, together 
with the frequent complaints and 
repeated requests for more effective 
means of control, prompted the authors 
to make the present study of this insect 
as a greenhouse pest. 
NATURE OF INJURY 
The injury results almost exclusively 
from the feeding done by the larvae. 
Since the length of the larval period is 
slightly more than the combined egg 
and pupal stages, ample time is provided 
for them to become exceedingly trouble¬ 
some and cause considerable damage. 
Feeding is normally restricted to the 
lower surface of the leaves, although on 
some host plants, as cineraria and 
chrysanthemum, the larvae have been 
observed to attack the upper surface 
and the bloom as well. At first the 
larvae skeletonize the foliage by eating 
small holes in the underside of the 
leaves so that only the upper epidermis 
remains intact. The injured areas 
which become pitted later coalesce 
and present a silvery appearance. As 
they grow older the larvae may devour 
the entire leaf tissue. As their com¬ 
mon name implies, they spin a slight 
silken web, or tie two contiguous 
leaves together to form a shelter within 
which they remain while feeding. They 
develop voracious appetites, and when 
present in considerable numbers cause 
severe injury to the plants attacked, 
not only disfiguring them, but actually 
destroying the leaf surface to such an 
extent that the plants die (PL 1, 
A, B). When the food supply be¬ 
comes exhausted they crawl away to 
other plants, and since they are able 
to feed on so many different varieties 
the infestation is spread very rapidly 
throughout the houses. 
ECONOMIC IMPORTANCE 
Although an apparently well-estab¬ 
lished pest in this country, the leaf-tyer 
intermittently causes such severe injury 
on certain greenhouse crops, especially 
chrysanthemums and cinerarias, that it 
demands prompt attention when a 
house has become infested. Consid¬ 
ered primarily as a greenhouse pest, the 
citations below give some idea of the 
seriousness and the extent of damage 
which it may inflict. These include 
only a few of the more recent com¬ 
plaints and appeals for assistance which 
have been received by the Bureau of 
Entomology, although numerous early 
records are on file which might be men¬ 
tioned further to emphasize the poten¬ 
tialities of this insect. 
In 1909 it was reported from Port¬ 
land, Oreg., as causing serious injury to 
violets in greenhouses, and in the same 
year a correspondent from Adrian, 
Mich., reported the larvae as being 
“present by millions on chrysanthe¬ 
mums, and devouring the plants so 
that it was impossible to secure cut¬ 
tings.’’ In 1912 a report from Hunts¬ 
ville, Ala., indicated that “two houses 
of chrysanthemums were stripped of 
their leaves, which only two weeks 
before had shown promise of a fair 
crop.” In 1919 the senior author vis¬ 
ited a florist in Vincennes, Ind., and 
1 Received for publication April 22, 1924—issued January, 1925. 
3 Sometimes referred to as “the parsnip web worm,” ‘‘the chrysanthemum leaf-skeletoni zer,” and “the 
celery borer.” 
3 Order Lepidoptera, family Pyralidae, subfamily Pyraustinae. 
Journal of Agricultural Research 
Washington, D. C. 
(137) 
Vol. XXIX, No. 3 
Aug. 1, 1924 
Key No. K-149 
