The control of the two-spotted mite on lima beans in California


Material Information

The control of the two-spotted mite on lima beans in California
Physical Description:
3 p. : ; 26 cm.
Elmore, J. C ( John Clifford ), b. 1896
United States -- Bureau of Entomology and Plant Quarantine
U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:


Subjects / Keywords:
Lima bean -- Diseases and pests -- California   ( lcsh )
Plants -- Effect of sulfur on   ( lcsh )
Two-spotted spider mite -- Control   ( lcsh )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


General Note:
Caption title.
General Note:
General Note:
General Note:
"February 1944."
Statement of Responsibility:
by John C. Elmore.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030290036
oclc - 779853536
System ID:

Full Text

L'taited Statee Department of Agric-u--t6re
Agricultural Research Administration
Bureau of Bntomology and Plant Quarantine


By John C. 1lmore, Division of 21
Truck Crop and Garden Insect Investigationfr

The damage caused by the two-spotted mite to lima beans in
Orange and Los Angeles Counties, Calif., since 1941, has made control
measures necessary. Sulfur has long been recognized as the remedy
for this pent on cultivated crops, but its application haa not al-
ways resulted in satisfactory control. experiments made during 1943
to determine when and how to apply sulfur to lima beano for mite con-
trol and to develop supplementary measures of control have led. to the
suggestions given in this circular. These should aid the bean grower
in OClifornia iL protecting his beans.

When to Apply Sulfiur

Lima beans in southern California can be protected from appre-
ciable mite injury by one or two applications of *conditioned' dust-
ing sulfur. The period in which applications are made, with respect
to crop growth and site infestation, is the important factor. It has
been found that, to be most successful, sulfur should be applied with-
in a period from 4o to 60 days after planting. The mites do not be-
come numerous enough to damage the crop until more than 40 days after
planting. On the other hand, applications need not be made later than
60days after planting to protect the plants for the rest of the season.
The dusting period for beans planted May 1 would be from June 10 to 30
and for those planted May 15 it would be from June 2?5 to July 15. Dur-
ing these period, the plants are small enough to permit dusting equip-
ment to pass through without plant damage and to make control possible
by use of a moderate amount of eulfar per acre. Experimental plots
dusted 30 days after planting became heavily Infested before harvest-
time. "P'l-ta 4-.sted 67 to 77 d&ys after planting required a larger
amount of wuLifar per acre, and the plants were damaged because they
were too large to allow the dusting equipment to pass through freely.

- - - - - - - - -- -- -

The amae 'two-spotted mite* is proposed for Tetranychue
blnaoulatu.. HArvey, one of the several sjpucia that have been known
as ommon red spiders, or spider mites.

The author wishes to acknowledge the cooperation and a*-
sistance of the Departments of Agriculture of Orange and Los Angeles
Counties in the field work done on tnim problem.


Dusting should be done when there is little or no air movement
either at night or during the morning before the wind, becomes too strong
to permit thorough coverage of the plants.

Number and Rate of Applications

In situations not previously subject to serious mite damage, such
as localities where alfalfa is not being grown, one application of dust-
ing sulfur at the rate of 30 pounds per acre, 45 to 50 days after plant-
ing, is recommended. In localities subject to early or heavy mite in-
festations* or where there is a possibility of serious mite damage, two
applications of sulfur should be made, at 30 and 50 pounds per acre, re-
spectively, the first 40 to 45 days after planting and the second about
2 weeks later. The second application need not cover more than 64 mar-
ginal rows on each side of the field and a border of the same width
across each end.

Dusting Xquipment

The most satisfactory dusting machines for lima beans are of the
row type capable of covering eight rows at a time and mounted on, or pulled
bye tractors. It is very important to get the dust evenly distributed an
the under sides of the leaves. This can be done by using dusting machines
equipped with nozzles to direct the dust to both sides of each row. If
one outlet per row is used, the dust can be directed to the under sides
of the leaves with a T nozzle carried between the rows. If two outlets
per row are used, the nozzles should be so directed that the dust strikes
the plants from both sides and from below. In the case of 8-row dusters,
larger air volume and less friction will be obtained with eight 2-inch
tubes or outlets than with sixteen 1*-inch tubes. When nozzles or tubes
become clogged with dust material, they may be cleaned by running a small
amount of scouring sand through the machine.

The cost of custom dusting in 1943 ranged from $2.50 to $5*00
per hour for labor and equipment, plus $1.00 to $1*65 per acre for
sulfur. With 5-row dusters, from 8 to 10 acres were usually dusted
Zer hour. This dusting resulted in an increased yield ranging from
; to 500 pounds in some fields as compared with the yield from un-
treated areas within the fields*

Indirect Control

Any practice that reduces the number of mites on other nearby
infested plants early in the season will tend to reduce infestation in
the bean fields. Therefore, the treatment of alfalfa, roadsides, or
other sources of mite infestations with sulfur early in the season is of
value. Likewise, the destruction, along roadsides and ditch banks, of
morning-glory plants and other weeds that are infested with the two-spotted


mite will help to control this pest.

Caution: Dust goggles should be worn when sulfur is being
handled, since it Is irritating to the eyes. Eye irritation is much
3or0 severe during dlusting operations than at threshing time. Unless
the amount of sulfur used per acre is far in excess of the amount re-
ommeaded, eye irritation at threshing time it slight and is usually
not noticeable until the eyes and face are washed* Precaution should
be taken to prevent the sulfur from igniting during dusting operations.
Nubber-tired tractors and dusters should be grounded by a dragging
chain. Sulfur should be kept away from hot motors and motor exhausts.

Description and Habits

The two-spotted mite, or common red spider, is a tiny spider-
like creature not quite large enough to be readily seen with the
naked eye. It is usually reddish, but the color may range from
yellow, orange, or brown, to green, and often, but not always, it
has two minute dark spots on the upper part of the body. Several
kinds of spider mites will feed on lima beans, but during 1943 the
two-spotted mite was commonly found on this crop. With the latter
the green color may predominate during midsummer when the plants
are green and succulent. However, many red, yellow, orange, or
brown two-spotted mites may always be found. As the season advances,
post of the mites may be orange or red.

The adult females lay 6 or 7 eggs per day. The young mites
that hatch from these eggs grow very rapidly and may mature in 10
days, Under low temperatures they do not develop so fast, but under
high temperatures mites increase so rapidly that they seem to appear
suddenly in lima bean fields and may cause considerable damage be-
fore they are noticed.

The two-spotted mite is able to live and develop on a wide
varietj of plants. It is difficult to name a cultivated plant upon
which it has not been found, and after the beans have been harvested
it will feed on almost any available weeds. Morning-glory is a com-
mon food plant, and alfalfa is the most conspicuous cultivated food
plant associated with lima beans. The mites are apparently able to
survive the winter and build up in the spring more successfully on
alfalfa than on other plants around lima bean fields. By the time
the beans are up, the mites may already be developing on alfalfa.
In many bean fields, especially in those formerly In alfalfa, the
mites are often present and well distributed on the plants by the
time the trifoliate bean leaves appear. The cutting and hauling of
green alfalfa is a well-known means of scattering the mites. This
dispersal is especially noticeable in bean fields to the leeward
of alfalfa fields and along the roads where stalks of hay are lost
from the hay trucks as they pass. Weedy ditch banks and roadsides,
as well as farm gardens and home yards, are likewise important
sources from which mites spread to nearby bean fields.

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