'V. POTATO INVESTIGATIONS LABORATORY
Mimeo Report 57-3 October 1, 1956
RECOMMENDATIONS FOR THE CONTROL OF INSECTS ATTACKING IRISH POTATOES
IN THE HASTINGS AREA1
Dale M. Norris, Jr.
General Control Considerations
In order to consistently produce a crop of Irish potatoes that will command
the highest current market price, a well organized insect control program must be
conducted. Contrary to some beliefs, such a program consists of a number of other
aspects besides the proper use of proven insecticides at recommended dosages. In
fact, the use of insecticides should, in general, still be considered as a stopgap
control measure. However, it is obvious in the case of a crop such as Irish pota-
toes, which involves a relatively high potential cash return per acre, that all
populations of deleterious insects on the crop must be kept at levels where their
activities do not reduce the yield or damage the quality of the product. In such a
situation, insecticides generally provide the most consistent means to this end.
Nevertheless, the progressive farmer should always do his best to utilize the follow-
ing other important methods of insect control:
In the case of potatoes, there are numerous insects; birds; rodents;
other animals; and microorganisms such as fungi, bacteria,and viruses that
are predacious or parasitic upon the insect pests of this crop. If the
farmer is aware of these organisms and does his best to promote their
activities, his need for insecticides will be lessened.
In conducting the various steps in preparing the land; planting,
cultivating,and harvesting the potato crop; and establishing the
customary summer cover crop, there are certain practices which interrupt
and discourage the life cycles of the various insect pests. A farmer
should be constantly on the alert for ways in which he can alter his
cultural practices to aid in the control of insect pests.
One of the major factors in determining the magnitude of an insect
population is the climate. The upsurge of such a population from a very
low level to a high destructive size is frequently due to a favorable
season from the general. climatic and weather standpoint. For example,
relatively dry warm periods generally favor insect multiplication and
wet cool weather usually hampers insect activities. It is therefore
highly important for the farmer to consider these variations in weather
in his insect control program.
1 Revision of Mimeo Report 56-3 by T. M. Dobrovsky.
In all major agricultural areas there are various forms of regu-
lations and restrictions on the movement of crop produce. These laws
are frequently concerned with the control of insect pests and are enacted
to aid farmers in their battle against insect pests. Because of this,
the farmer should always conform with the laws and assist in promoting
their enforcement where possible.
Toxicity Of Insecticides To Humans, Other Animals And Plants
Insecticides should be handled with respectful caution. In nearly all
cases, the materials that are deadly to insects are likewise deadly to humans,
other animals,and even some plants. Insecticides differ markedly in their
degree of toxicity to various forms of life and therefore some must be
handled with much more care than others. Parathion, TEPP, systox, EPN, and
endrin represent the most toxic extreme in insecticides. While methoxychlor,
certain miticides,and plant-derived insecticides such as pyrethrins are
classified as of distinctly lesser toxicity. Nevertheless, these of the
latter group are poisons and must be treated as such. In using insecticides,
there are two rules ha the grower should never violate in order to main-
tain the welfare of all parties concerned. These are as follows:
Follow the instructions on the label of the insecticide container
to the .er".---
This includes the instructions for the safety of the person
applying the insecticide. It pertains to the dosage applied per
acre, and to the established interval that must be allowed between
the last application and harvest in order to assure compliance with
residue tolerances. Lxity in any of these respects fosters need-
less loss of human life, damage to crop plants; production expense,
liability to federal and state reprimand, and possible confiscation
of valuable farm produce.
If there are questions pertaining to any phase of the use of insecti-
cides consult a specialist in entomology before proceeding.
Such persons should have the needed information at hand or know
where to obtain it and thus avoid complications that may result from
careless use of these poisons.
Potato Insect Control Program
In applying insecticides to the soil for the control of soil-inhabiting
insects, the main problems are to apply the material at the proper time and
in the proper manner. Due to the long residual action of our better soil
insecticides, the time of application in itself is not extremely important,
but the manner of application is very important. In general, the recommen-
dations for such treatment of the soil state that the material should be
disked into the top 4 to 6 inches of the soil immediately after application.
Such has been the general recommendation in this locality, but there are, at
least, two major shortcomings involved in the use of this method with our
practice of planting potatoes on ridged rows following a summer cover crop
that also furnishes food for wireworms and other soil insects.
Spray or dust an application of 2-3 Ibs. actual heptachlor or aldrin
per acre to the surface of the ridged rows 2-3 weeks prior to planting
(1) The cover crop is listed under in preparing the
land for potatoes, and placed in a nice neat roll in the
bottom of each ridge, where it can serve as a protected
source of an abundance of food for the wireworms, etc. until
the tubers develop. Then it's just a matter of moving
upward through a non-treated area in the heart of the ridged
row into the tuber zone.
(2) This method of applying the insecticide to the
surface of the ridged rows and then redisking and/or re-
bedding at a time 2-3 weeks before planting potatoes only
provides the outer few inches of the ridge with treated
soil. If the populations of wireworms,etc. are already
established in the soil, they can do extensive damage to
the tuber crop and not need to encounter the applied
Because of these shortcomings of the current method; plus the apparent
development of insecticidal resistance in wireworms, a new split appli-
cation method for the control of wireworms and other soil insects is
proposed based on our current knowledge.
New Practice Split application for the control of soil insects.
This method of controlling soil insects, particularly wireworms, con-
sists of two separate practices which remedy the shortcomings of the cur-
rently standard spray method and also up the dosage in an effort to overcome
the developing resistance factor.
(1) After the summer cover crop has been knocked down and
chopped up prior to listing it under, the cover crop and soil
surface are sprayed with 2 lbs. actual heptachlor or aldrin in
100 gallons of water per acre. Then the treated cover and soil
are listed under immediately. This will now result in a new
ridge in which the cover crop and central soil in the ridge are
treated with insecticide.
(2) The second portion of the treatment involves essentially
the current practice. This is to partially disk down the ridges
and to spray the soil surface with 2 Ibs. actual heptachlor or
aldrin 2-3 weeks before planting time and then redisk and rebed.
This combination of operations will provide a ridged row in which nearly
100 percent of the soil will be treated. Also, the wireworms will not have
the abundance of untreated cover crop to carry them over until the potatoes
In spraying insecticides on the soil be certain that the nozzles
are placed on extensions which place them within 6 inches of the ground
surface and arranged so the entire soil surface is covered uniformly.
The use of a pressure of only 200 Ibs. will reduce the amount of spray
lost in the air. Be sure that the spraying operation is done when there
is little or no wind and disk and/or rebed immediately.
Use 1 quart of 25% DDT emulsion and 1 pint of 25% para-
thion emulsion (or j pint of a 50% parathion concentrate) in
100 gallons of water per acre. Spraying with this combination
about every 10 days will generally provide satisfactory control.
Apply a mixture of 5% DDT and 2% parathion dust at the
rate of 20-30 lbs. per acre every 10 days.
Regular spray applications should begin when the first aphids or other
foliage feeders appear. These materials may be combined in the same spray
solution with the fungicides used to control late blight.
The use of the insecticides recommended for control purposes on
potatoes involves no poison residue problems. In case, some other material
is to be used, it is suggested that its status with regard to residue
tolerances be clearly understood and honored.
Common Insect Pests of Irish Potatoes in the Hastings Area
Insect Insecticide 100 gals./A or General statement
___________ ____ total dust/A
Aphids 25% parathion emulsion pint
-2 parahion dust 20-25 bs.
-25 DDT emulsion I quart Controls small infestation
Cutworms '70% texaphen emulsion 1 pint Frequently bother young
'0 oxa ipene- 'st i-25-30 Ibs. newly emerged potato
2i'j5% T .mulsion 1 auart plants.
_____. T. dust ... 25-30 ibs_.
Leaf-footed 2;% parathion emulsion 1 pint
plant bug, 2 prathion dist 25-30 ibs.
green stink bug 72~ chordane emulsion _l pint ._ ,
Serpentine 25 parathion emulsion 1 pint
leaf-miner E2parathon'aust 0-30J bs. .......
Wireworms Aldrin emulsion Apply as discussed above in
(2 Ibs. actual/gal.) 11 to 2 gals. portion under soil insect
reptachlor control. Split application
(2 Ibs. actual/gal.) 1 to 2 gals. proposed rather than the
single spray application.