360 
FIRE BLIGHT 
rill believes that in the orchards and nur¬ 
series of Wisconsin leaf hoppers ( Empo - 
asca mali ) are the most important carriers 
of blight during July and August. 
PLANT filFE CHIEF DISTRIBUTORS. 
In Kansas, according to J. H. Merrill, 
(Bee Inspector’s Report, Iowa, 1916, page 
33) plant lice, which are the most common 
and widespread sucking insects in Kansas 
orchards, have been found to be the chief 
distributors of blight bacteria. Aphids, 
which had been permitted to crawl thru 
pure cultures of fire blight, were then 
placed on terminal twigs and enclosed in 
cheese cloth to exclude all other insects. 
These twigs blighted and were the only 
ones that did. Furthermore, it has been 
observed that in seasons during which 
plant lice are most abundant, fire blight is 
also most prevalent. In 1913 in Kansas 
orchards they were very common and so 
was fire blight; but in orchards in which 
they were controlled there was little blight. 
In 1914 there were few aphids and little 
blight, and this reciprocal relation was 
again noticeable in 1915 and 1916. Merrill 
says that the amount of blight can be de¬ 
creased by controlling the aphids. SteAvart 
also observed that in apple nurseries fire- 
blight epidemics follow rapidly in the wmke 
of aphid epidemics. 
SUCKING INSECTS IMPORTANT DISTRIBUTORS. 
In New York orchards fin July, accord¬ 
ing to SteAvart, the tarnished plant bug and 
several other sucking insects are important 
distributors of blight. Finally D. H. Jones 
has added to the list a beetle of the genus 
Scolytus, and on further observation many 
other insect carriers will doubtless be dis¬ 
covered. There is no lack of puncturing 
and biting insects in immense numbers, 
which, it is certain, are active in spreading- 
fire blight. 
BEES NEVER PUNCTURE LEAVES. 
It Avill be noticed that all the insects 
mentioned in the two preceding paragraphs 
have mouth-parts, Avhieh can puncture or 
bite thru the epidermis of the leaf. In this 
way the germs are placed in the tender tis¬ 
sues, multiply rapidly and produce infec¬ 
tion. “Insects,” says Merrill, “with suck¬ 
ing mouth-parts are admirably suited to 
this purpose.” Stewart and Leonard state 
that except for blossom blight the bacteria 
can not gain an entrance in the host tissue 
and produce infection except thru a wound 
or the punctures made by insects. Honey¬ 
bees never puncture the leaves; indeed, 
under normal conditions they never visit 
them; nor do they puncture the floAvers of 
the apple or pear, for the nectar is easily 
accessible on a flat disc. If, however, 
blight is chiefly distributed by the wind, 
the pricking in of the germs, altho a great 
advantage, is not an actual necessity. 
AN ALIBI FOR BEES. 
It is clear that all infection of the leaves 
and twigs must be due to other agencies 
than the honeybee, since the latter confines 
its visit strictly to the floAvers. Further¬ 
more, since bees visit the trees only during 
blooming time, it is only during about two 
weeks out of 14 or 15 that it can be ac¬ 
cused of being a carrier of blossom blight. 
Let us now inquire if honeybees are re¬ 
sponsible for the spread of blossom blight. 
As they do not visit the foliage they can 
not be the agency, which, in the first place, 
brings the blight to the bloom. In Kansas 
orchards, Merrill states, this is done by 
plant lice, which in large numbers enter 
the apple buds and suck their juices before 
they open, at the same time inoculating 
them with blight bacteria. Thus the flow¬ 
ers blight in the bud before bees begin 
their visits. Once the bloom is blighted 
it is no longer attractive to honeybees; for, 
if we remove, the petals of a healthy pear 
blossom, bees will at once cease to visit it, 
altho they will continue to visit other flow¬ 
ers near by. Twenty-three pear blossoms 
received 24 visits from honeybees in half 
an hour; the Avriter then removed all the 
petals and in the half hour folloAving there 
Avas not a single visit, altho the denuded 
blossoms contained nectar and the bees of¬ 
ten visited other flowers near them. Thus 
bees might fly indefinitely between the un- 
contaminated blossoms without disseminat¬ 
ing the blight. But it must be remembered 
that the bloom is visited by many insects 
besides bees, especially by flies and beetles 
which do not exhibit flower fidelity. As 
they alight on the leaves both in search of 
food and by chance, and Avill freely visit 
the blighted blossoms, they can not fail to 
