30 
HORNBERGER’S SERVICE 
HAMBURG, N. Y. 
GLADIOLUS THRIP AND CONTROL MEASURES 
Thrip in their adult stage are flying insects. They are very small, 
and for that reason are likely carried great distances by high winds, as 
are many other very small insects. In my personal opinion, I think one 
of the most prolific sources of distribution is by the cut flower method. 
Cut glads are now shipped and re-shipped about 12 months in the year, 
with the industry so large in the southern states, there is almost a con¬ 
tinuous movement of cut flowers and I think it can readily be proven 
that many cut flower spikes of buds or bloom can harbor many adult 
thrip without much, if any, damage showing on buds or bloom, to the casual ob¬ 
server. You can take many such blooms and strike them quite a sharp blow and 
adult thrip will fall off the flowers. Such flowers may be given to our near neighbors. 
They may purchase them grown near or far, or they may be placed in local ceme¬ 
teries. As soon as the spike dries up, it is concluded that Mr. Thrip will look for 
a new home and this may be your gladiolus patch, large or small. For this reason, 
even where you plant 100% clean bulbs you may very easily secure some outside 
infestation each growing season. 
The Bureau of Entomology. Department of Agriculture, Washington, D. C. 
have stated that thrip (glad) do not overwinter outside where the winters are cold 
enough, so that soil is frozen for some time, however it is possible for thrip to 
overwinter on your bulbs, and if your storage temperature is above 50 F. in winter, 
the thrip will feed on bulbs, causing a brownish, rough appearance on flesh of bulb, 
referred to as “russeting.” However, a similar appearance is sometimes caused by 
action of chemical substances like ammonia, etc., from hen manure. So, it requires 
some real discrimination to be sure it is damage from thrip and if it is, you should 
have no trouble locating thrip or their larvae, underneath the “husk” of your bulbs. 
The same is true when your plants are infested in your garden. There are certain 
indications of their activity. The plants are likely to have a “rust like” appear¬ 
ance near the leaf joints as well as near the soil level and the green foliage is likely 
to look streaked before the bud spike appears. On such plants as are infested, you 
will find the thrip in the leaf joints, after the buds form, most of the thrip on such 
a plant, will concentrate under the bud sheath of the buds, not an easy place to 
reach with a spray. By removing all infested spikes from infested host plants in all 
light infestations, we get most of the thrip on such plants, as they have largely con¬ 
centrated in bud spike, burn or destroy such spikes and you will do much to main¬ 
tain a high degree of control. Weekly spraying or more often if required, with 
some good spray material will do much to keep plants protected from thrip develop¬ 
ment. Start the spraying when glads are three to four inches high. We have not 
had to resort to general field spraying for the past 8 years due to proper control 
measures used. 
THRIP DAMAGE: In very light infestations thrip may go almost unnoticed by 
the average person, as there is such a small amount of the “feeding larvae” the 
adults move about quite rapidly, while the larvae are concentrated where they hatch, 
and feed, so those places show distinct results of their activity. In very warm 
climates or in so called “hot spells” in the north, where temperatures often hover 
near 85-90, night and day for weeks, the conditions become ideal for the rapid 
increase of thrip. Even from moderate infestations, the general rule seems that with 
very light infestations, in moderate northern summers, thrip may not cause enough 
damage to require spraying. We are told that the complete life cycle of gladiolus 
thrip is less than 6 0 days, and that thrip eggs held for 6 0 days in cold storage 
would not incubate as thrip do not feed, hatch or develop at storage temperatures 
below 5 0 F. It has been concluded that a storage about 4 5 F. maintained for 60 
days or more of the coldest part of the winter, should do much to assist us in con¬ 
trol measures. Using a highly recommended dip, like Corrosive Sublimate, 1 oz. of 
C. S. to about 7 gallons of water and bulbs submerged in this for twelve hours, 
should produce the highest possible control results. Use such solution twice, then 
discard and make a new batch. The C. S. dissolves slowly in cold water by using 
hot water to dissolve and adding enough extra cold water to make 1 oz. to 7 gal¬ 
lons of water, we have a satisfactory double purpose dip, as this has been used for 
years in scab control measures. Bulbs may be permitted to dry off or may be 
planted wet, right from the dipping material. Do not use metal in contact with the 
C. S. solution. Where your storage rooms are warm or above 5 0 F. for much of the 
