Control of scale insects and whitefly by parasitic fungi.


Material Information

Control of scale insects and whitefly by parasitic fungi.
Series Title:
Writings and Speeches 1891-1920
Physical Description:
Physical Location:
Box: 1
Divider: Articles, Speeches and Other Writings
Folder: Control of scale insects and whitefly by parasitic fungi.


Subjects / Keywords:
Agricultural extension work -- Florida.
Agriculture -- Florida -- Experimentation.
Agriculture -- Study and teaching -- Brazil -- Minas Gerais.
Agriculture -- Study and teaching -- Florida.
Citrus fruit industry -- Brazil.
Leprosy -- Research -- Brazil.
Minas Gerais (Brazil) -- Rural conditions.
Escola Superior de Agricultura e Veterinaria do Estado de Minas Gerais.
Florida Cooperative Extension Service.
University of Florida. Agricultural Experiment Station.
University of Florida. Herbarium.

Record Information

Source Institution:
University of Florida
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All applicable rights reserved by the source institution and holding location.
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Full Text


The question o' control or insects by means or natural enemies

has received much attention, at times attaining to what we iiight

call notoriety. In America the matter has b.--n given probably

more serious and systematic study than anywhere else in the world,

at least this would seem to be the case from a study Irl t.he lit-


Among the workerss alonir this line may be menir.:iecd ro. Sln',

Forbes and j3urrill. 1uch wnrK has blen done by each onr thse

men but ror want or time and opportunity the i'ollow-up -'r.rP could

not .be continued, antld consequently i:much nor the gr.od has been lost.

In Florida the climatic conditions seem especially fa\,,oraile

to the use of such methods ror tUe control or gregarious insects

especially tion:.e belonging to Le icdae and levrndld.a. ir-

,sects that lead a more solitary life do not lay thw;selves open

to suMf vulnerable attacks Aas may occur to insects that are in-

cliJed to be gregarious and live a stationary existence during a

portion of their lie cycle.

The period or this work in Florida began in about 18y4, "hen
hAes ao 'evdj. Aru
SDr. Webber discovered a parasitic Achersonia o lleyrod. A)r, ut

K1'?., the same time the speaker discovered Sphaerostilbe coccphila

as parasitic upon san Jose scale. This discovery was not acci-
'',.^. dental, but ol a onS derabLe a: ount 0" time a"d .-tudy gd

Sn-gT VH to deter-inin&1 the c use or,,natural mortalit"

San Jose' scale. The observations were published, and received

,with an unusual amount o. incredulity.

,1---. :
,,.*. _

2ung;i Widely used in Florida.

Nowhere else in the world have ilmgi been so widely and suc-

cessfully used ror the control or insect pests as in Florida. I

have already called attention to the ract that climatic conditions

are especially favorable to the spread or insect diseases. Pecul-

iarly enough the particular Vorms or insects which are most advan-
tageously controlled in this nay are very abundant in thq state.

The species are nu erous and the Indi'iduals belonging to the species

likely to be present in excessive numbers ahen conditions are V'avor-

able to their health.

The rainy season occurs in the summer ime when the temperature

Is highest producing an atmosphere nat may be likened to the air

in a moist chaimrber. The condition or .;rowth or the trees is like-

wise such as to produce an abundance of shade and Iurther reduce

the evaporation that would occur froyn rdliation. With the intense

sunlight comes abundant development or roliage. The sunlight, how-

ever does not become so severe as to be g to the develnp-

ment or follar 9. under these natural conditions the intro-

duction and p 0 or IUgi becomes an easy matter compared with

the conditions in regions avhere the atmosphere may be dry during

the warm portion of the year or cold during the moist portion or

the y-ar.

These natural conditions oeing present and favorable to the

growth or rungi, the Experiment Station has encouraged so far as

possible the development of private enterprise rnr the dissemination

of scale and whitefly diseases. During the spring and surmm-er

of 1909 one man alone with his helpers treated 1e7,000 citrus trees

with asia spores toLlt whitefly'. This vork was done

ST 3
under contract charging aZ per tree treated. This compared with
spraying with insecticides ./as a very light cost, since spraying
the 2ame trees with insecticides wonur] have cost about s5/ per tree.
-o r4e_" 'ti
During ly10-11 we ippe ato itve- record as to the number of
trees treated, but it would go up into tnhe millions.
The introduction o' r, ngi ror scale insects is carried on in
a somewhat different way th-an -we havt introduced the rungi against
whitefly diseased scale are introduced into healthy colonies.
This can be most easily accomplished by. transferring sprigs or'
pieces or branches upon which diseased scale occur; placing these
in contact or nearly so with the healthy scale readily transfers
the disease, while rains, dews and other conditions do tie rest

Naturally in the introduction of diseases there is an opportune
and inopportune time at which to do the -Jork. Under advantageous
climatic conditions very little difficulty is experienced; under ad-
verse climatic conditions the work has to be repeated. The Experi-
ment Station has carefully worked. out the details connected with
the successful introduction or the various rungi. At times rather
long periods occur ihen the fungi are not readily Introduced or
there may be other condition existing in the grove which militate
against the rapid spread or tne insect diseases. during such periods
It becomes important' to use the ordinary artificial remedial meas-

AS these details, together with the names or different species
o' fungi, :Ls well .is the names or the species or hoot insects occur
in the Experiment Station bulletins, I will not burden my hearers
with reciting them here.

Reasons rnr Failures.

The most important and serious reason for failures with our

work has been lack on sclentiric Knowledge as to what conditions

were favoraOle- and what ,'ere unravorable.ror the- ralpia development

of diseases amwnng the insects. inere is no difl'culty in securing

the Inrections, though onten in this line the j. .'1

more or less trouble. Arter studying the question ror a decade

and a haLr or more, and doing so in a technical and systematic way,

many facts have been brought together. These can now be so r.rmu-

lated that the average layman can make use or the inforTation.

Many; times, however, it is difficult for the non-technical man

to understand that the processes must be carried out e :actly as di-

rected 'by the scientific man. Tne laynrinn .'ill not understand Why

some oT.her method, some snort cut, which apparently accomplishes

the same work,,will not do just as well.
Another reason ror the lack or popularity is the fact that

zealous people have over advertised this method of controlling pests.

T'is is not so .llKely to be the case with the scent ist, since he

is likely to under advertise his discoveries, but the popularizer

of sclentiric material is likely to induce the layman to believe

that all he has to do is to introduce a. Lungus spore and then go

away and leave flS and th- fungus will do the rest. These same per-

sons would not be likely to advocate that it was possible to raise

a citrus ,!'rove by simply sowing a few orange seeds here and there

in our piney woods or hammock, yet his imagination l-ads jilm to be-

lieve that this Kind or careless work will be aLl right with the


Under the old methods when the dirriculties or securing a large

infection were not well unaerstoon, It frequently happened that the

introduction or the rungi gave negative results, and this naturally

led to condemning the method.

Opposition to the Method.

At Virst glance it would seem as though it was ridiculous to

talk about there being any opposition to this method of handling

agricultural pests. However, the scientist needs but to start in

the field until he will rind tin't there is real live opposition

to it.
The advance agent or A spraying manufacturer at once sees that

when scale insects are eliminated rrom the gr e his sales or
spraying machinery must necessarily be reaucea, consequently he

makes it his business to repeat and r"-repeat all the stories or "

failures and supposed Iailures. It is not unusual to rind the lay-

man who considers the introduction or rungi diseases a failure long

before the infection hMs had time to kill onr the rirst lot or in-

sects that were infected, and long before the rungi have had time

to fruit and make a secondary or tertiary infection.

Along witn the spraying machine man comes also the manufacturer

or insecticides and his agents. nTeir business is necessarily in-

terfered with as soon as the natural methods for the control or

scale insects are advocated, and since the profits, especiLly on

the proprietary brands or insecticides are quite considerable he

naturally believes that handsome stories must be told to keep up

the popularity or his particular brand.

Peculiarly enough, and from a source that ,vould be un-

suspected, opposition comes ronm old-line entomologists. 'or the

most part these men have been trained In regions where cLimatic

conditions are not favorable to the intrrcductirn and spread r.r

'ungus diseases or insects. The Literature has been pretty thor-

oughly reviewed by them ana studies mace 01 the situation, their

deductions being based on experiments ana work done under con-

ditions quite di rerent rrom those occurring in Florida and to

some extent along the Gulr Unast, vsA these entomologists, as a

rule, come into the field in a sceptical state or mina ir not

indeed in a prejuaiced one, and not infrequently miss the point al-

together by their want 0!' familiarity with the runigus side on their


uis seminat inn a1 Iniormatir.n.

under the conditions it has been necessary ror the Experiment

Station, practically single-handed, to disseminate the information

and to establish his method or handling scaLe insects and whlterly.

Like all other methods or handlln:; these pests it Trust be used

with discretion ;.nd with knowledge. There are conditions unaer whidii

the method will succeed only indifrerently and where the artificial

methods or control should be used.

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