until the micro-organisms are produced in 
sufficient quantity for massive field testing. 
Furthermore, the whole problem of the 
general use of a microbial agent is not ap- 
parent until it is mass-propagated, An ex- 
cellent example of the problems that arise 
can be illustrated by the mass-production of 
the organism Bacillus thuringiensis var. 
thuringiensis Berliner, About 1956, Bioferm 
Corporation, Wasco, Calif., pioneered the 
production of this bacterium and was closely 
followed by such companies as Nutrilite 
Products, Inc., Merck Sharp and Dohme, 
Rohm and Haas, and the Grain Processing 
Company. The resulting cooperative work 
among these companies, interested labora- 
tories, and Government laboratories aiding 
in field testing made available a huge amount 
of encouraging data concerning the efficacy 
of this superb control agent. However, a 
large number of unexpected problems arose 
from the initial work--problems of fermenta- 
tion, of proper bioassay, of specificity, of 
formulation, and so forth. Most of these 
problems have been solved or their solution 
is in hand. None of these very important 
problems would have been solved by this time 
without mass-production of the organism. 
During the past two decades, we have been 
increasingly aware of the great potential of 
insect viruses as insect-control agents. 
You are probably aware of the following 
types of insect viruses: (1) Nuclear poly- 
hedroses, (2) cytoplasmic polyhedroses, 
(3) granuloses, (4) polymorphic inclusion 
viruses, and (5) noninclusion viruses. 

There are, collectively, about 225 species 
of insect viruses now isolated. Of these, the 
nuclear polyhedroses (107 species), the 
granuloses (35 species), and the cytoplasmic 
polyhedroses (80 species) are the most likely 
candidates for insect control. 
Several of these viruses have been tested 
in the field. The virus materials for most 
of these tests were obtained from insects 
reared on the natural plant at one time during 
each year when the larvae were available. 
More detailed information on these methods 
is available from an article by Martignoni 
(1964). 
Thus, we find that less than 10 percent of 
the viruses have had field trials. The reason 
is that production of sufficient virus material 
was too costly and time consuming for many 
of the interested Government agencies to 
attempt. 
Fortunately this stage of helplessness in 
insect pathology is almost over. By their 
intensive research, entomologists all over the 
world are amassing valuable information on 
techniques for rearing many of the economi- 
cally important pests on artificial or semi- 
artificial diets, permitting yearround, rela- 
tively inexpensive rearing of insects. 
If an insect can be reared after this fashion 
continuously, it is then almost always possible 
to devise a method of propagating the specific 
virus of that insect. 
Recently Ignoffo (1964) devised methods for 
producing the nuclear polyhedrosis of the corn 
earworm [Heliothis zea (Boddie)] (on cotton, 
the bollworm), that of the tobacco budworm 
Table 1.--Insect viruses 

Type of virus 


Estimated species Orders affected 

Nuclearmpolyhnedrosi's/yrerleretsketerelchelelelerciencl ere 
Cytoplasmic polyhedrosis.......... Spalchenete 
GranuilOsisiyarcrercrer: alicnchavedelel afretaleislieveleitons aietioheve 
Polymorphic inclusion virus.......... 500 
Nonineluswonvial vuStevekewerercieleherclerekerctelenereievers 


Number 
107 Lepidoptera and Hymenop- 
tera. 
80 Lepidoptera. 
35 Do. 
2 Lepidoptera and Diptera. 
5 Coleoptera, Diptera, 
Hymenoptera, Lepidop- 
tera, and Arachnids. 
229 Se 

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