The beet leafhopper in relation to the production of garden beet seed in central California

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Title:
The beet leafhopper in relation to the production of garden beet seed in central California
Physical Description:
Book
Creator:
Wallace, H. E
United States -- Bureau of Entomology and Plant Quarantine
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U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine ( Washington, D.C )
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aleph - 030284974
oclc - 779479038
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Full Text


)ARD


April 1943 Z-590
UNITED STATES DEPARTMENT OF AGRICULTURE
% .Agricultural Research Administration
Bureal of. Entomology and Plant Quarantine

TE BEET LEAFHOP PR IN RPELATION TO THE PRODUCTION OF
GARDEN B ET SEED IN CENTRAL CALIFOYMIA
By H. E. Wallace, G. T. York, and W. C. Cook,
Division of Truck Crop Insect Investigations


Garden beets have been .rown for seed production in the Sacramento
Valley of central California for many years. The seed is sown thickly in
root beds in August and September, to produce from 25 to 100 plants per
linear foot of row. No thinning is done in the fall, but in December all
the roots are removed from the beds and carefully inspected, and undesir-
able plants are discarded. Plants chosen for seed production are then set
out in large fields, being placed singly about J to 3 fe, t apart in rows
which are about the same distance apart. The tall seed stalks develop dur-
in the spring months, and the seed crop is harvested in the summer. This
method of seed growing enables the seed companies tb select the roots
rather carefully and also to produce the roots for a large final acreage in
relatively small beds. The total area devoted to root bads in central
California is probably less than 1,000 acres.

During the past 10 years the root beds have been subject to severe
damage by curly top, a virus disease carried only by the be-t of leafhooper
(Eutittix tenllus (Bak.)). The primary source of the liafhopDDrs causing
this damage is the large acreage of sugar beets grown in the Sacramento
Valley, which serves as a summer host to these insects. The fall brood,
produced on sugar b3ets and to a limited extent on weed hosts, drifts south-
ward through the Valley during September and October, infesting the garden
beet root beds, and often severely infecting them with curly top. The
fields in which the roots are transplanted a-re practically free from leaf-
hoopers during the winter months, and no further infection occurs until the
leafhoppers begin their spring movements the following May. By this time
the beets are so nearly mature that infection has but little effect upon
the seed crop.

From the foregoing discussion it may be seen that garden beets grown
for seed are -subj.eet to damage from curly top chiefly during the fall
months while they are in the root beds. The protection of this crop
against curly top depends upon controlling the leafhoppers in the root beds
or upon choosing locations for the root beds in areas where few lefhoppers
aopear in September and October.

NATU RE OF INJ-URY
Symptoms of curly to-o disease in the garden b3et are similar to those
in the sugar beet. They have been described by Severin (3) as transparent
venation, leaf curling, protuberances on leaves, increas-d number of side
rootlets, and others' These typical symptoms de'relop on be.ets planted in
late summer if they are infected during August, Septmriber, or early October.
Plants infected later than this rarely show any tyica.l symptoms.







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At sorting time the beet roots obviously infected are discarded, but
those roots infected too late toahew typical symptoms of the disease cannot
be detected and discarded. Roots that are diseased do not produce normal
seed stalks the following season. Since the roots are replanted singly with
wide spacing, the effect of fall infection on the seed yield is nearly pro-
portional to the number of roots that contain dormant or undetected disease
at the time of transplanting.

HABITS OF THE BEET LEAFHOPPER
In central California the beet leafhopper overwinters in the eastern
edge of the foothills of the Coast Range from Tracy south to the Tehachapi.
Mountains, and around the southern end of the San Joaquin Valley to the
Sierra Nevada foothills, often extending as far north as Portarvilie. Mi-
grations of spring adults from this area cover the entire northern part of
the State. During the summer three broods of leafhoppers are produced upon
cultivated host plants such as sugar beets, garden beets, and spinach, and
upon certain weed hosts. In the Sacramento and Salinas Valleys the weed
hosts are scarce, and sugar beets serve as the principal host. In the coast-
al areas all host plants are scarce except truck crops in restricted areas,
The leafhoppers move from summer hosts back to the foothills in the fall. The
life history and habits of the beet lnafhooper in California have been re-
corded by Severin (4) and Cook (1).

Since most of the curly top damage to beet roots occurs during the fall
months, the rost severe damage may be expected in areas through which fall
movements of leafhopp'rs are heavy.

INEFFECTIVEBSS OF DIRECT CONTROL 1_E2STJRES
No direct measures have been found to control the beet leafhopper on
garden beets grown for seed in central California. Romney (2) reported that
the application of a pyrethrum-in-oil spray increased yields of seedon sug-
ar beets and garden beets in Arizona, New M~lexico, and western Texas. How-
ever, in these areas the beets are sown thickly in large fields, and are not
transplanted. A pyrethrum-in-oil spray was tried on seed beds in central Cali-
fornia, but did not prove successful. Although over 90 percent of the leaf-
hoqpers were killed, a single spraying of the beds did not reduce the infec-
tion sufficiently to be practical. More or less continuous shifting of the
leafnopper population often reinfested beds shortly after spraying.

Trap crops of turnips and radishes planted between the bet rows nave
been tried to detract the leafhoppers from the beets, but without s~iccess.
The use of various possible repellents, both chemical and mechanical, has
also been without avail.

LOCATION OF ROOT BEDS IN DI SASE-FREE AREAS
Since no direct measures have been found to give satisfactory control
of the beet leafhopper in the garden beet root beds, the problem has been
solved temporarily by locating root beds in areas that ar3 relatively free
from leafhoopers dring.the fall. For several years surveys have been made
during the late summer and. fall to d termine the areas that seemed to con-'
tain small fall populations. These surveys have be:.n supplemented at times






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by experimental plantings by the seed companies. As a result of this work
it is possible to list and map certain areas where at the present time
plantings of garden beets for seed are relatively safe from curly top dam-
age in the fall. Some of these areas have been.tried and found to be
satisfactory, while others are given as oossible areas for future plant-
ings. In the areas shown on the map (fig. 1) beet roots will be relative-
ly free from curly top infection, but their production may be undesirable
for other reasons. At present no recommendations are made regarding con-
ditions other than those affecting the beet leafhoorer and curly top.

Certain precautions should be taken even in areas where very few leaf-
hopers are present. Fields selected for seed beet plantings should be
away from large areas of host plants, either weed hosts such as mustards,
Atriplex s-cp., and Russian-thistle, or cultivated hosts such as sugar beets,
garden beets, soinpoch, or turnips. The leafhooners from such fields, even
though present in small numbers, may cause considerable damage to the rela-
tively small root beds. A situation of this nature occurred at Clear Lake.
Garden beet root beds were satisfactory for a few years, but later beets for
canning were planted in the spring and summer, and the increased leafhopper
population on these plants shifted to the root beds in the fall.

In case root beds are desired in the same general area where host plants
are known to be present, it is advisable to locate the root bads on the
windward side of the host plants. This precaution is sometimes sufficient
practically to eliminate curly top damage in areas where prevailing winds
are persistent.

The coastal areas (fig. 1, A) are relatively free of leafhoppers. Very
few enter in the spring, and the climate is unfavorable for their develop-
ment during the summer. Small valleys 10 or 20 miles back from the coast
may have different conditions. In such areas it is important that the rcot
beds be on the windward side of any beet fields or weed host areas. Beet
roots have been grown to only a limited extent in one of the three areas
shown on the map. Conditions other than curly top may limit their pro-
duction elsewhere on the coast.

The Coast Range section north of San Francisco Bay (fig. 1, B) has
been found relatively free of leafhoppers during the fall months. In parts
of this -ection, particularly around Healdsburg and Santa Rosa, plantings
have been made for several years and are roving satisfactory. In the
southe?,storn portion of this area, around Suisun Bay and as f-r inland as
Vacaville on the north and Brentwood on the south, few leafhoopers orer-
winter at resent, 1.nd summer hosts are scarce. This area is out of the
main path of both their spring and fall movements, nd it remains relative-
ly free from leafhoppers during the summer and fall. However, Feme over-
wintering and spring breeding occurred in the hills bgck of 3rentwcod dur-
ing the dry years from 1930 to 1975, and it might occur agsin. It is also
possible that a very heavy movement in the spring may be deflected from
its normal course by unusual wind currents, and establish summer popula-
tions on one or both sides of Suisun Bay. For this renson it may be de-
sirable to consult the 'Modesto laboratory of the Bureau of Entomology and
Plant quarantine before establishing new root beds in dry years.







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A limited amount of survey work has ben done in the Sierra foothill
in the Sacramento Valley (fig. 1, C), Ind beet leafhonper populations have
always been low. This may be due to the scarcity of summer host-plqAts,I,.
and also of green plants that might hold leafhopper-s during the fall move-
ment. This foothill area would seem to merit experimental plantings, if
suitable land can be found' Such plantings should be abore the lowest
range of hills, to be out of the line of the general fallleafhopp'r movelk-.
ments.

One field of garden be'lt seed that is practically free from owly top
injury has been found in the Sacramento Valley. Since 1933 this f ield,
situated about 2 miles west of Sacramento, has produced beet roots tha are
practically free of disease, while those in other seed beet fields nearby
have been a Comrlete Icss. In 1941 no leafhorpers were found in this field,
and only 2 dise:.eed b-ets w3re seen, while a field of spinach 1 mile east
had 50 leafhor-er e pr 100 feet of row, and 70 percent of the plants showed
curly top infection. The reasons for this great difference in injury are
not known, and other safe locations for planting beets for seed in.the
Sacramento Valley can be determined only by experimental plantings.


LITERATURE CITED
(1) Cook, W. C.
1941. The beet leafhopper. U. S. Dept. Agr. Farmers' Bul. 1886,
22 pp., illus.

(2) Romney, V. E.
1942. The beet leafhopper ind its control on beets grown for
seed in Arizona and New Mexico. U. S. Bur. Ent. and
Plant Quar. E-567, 10 pp., illus. [Processed.]

(3) Severin, H. H. P.
1929. Curly top ymptoms on the sugar beet. Calif. Agr. Expt.
Sta. Bul. 465, 35 pp., illus.

(4)
1930. Life-history of beet leafhopper, Eutettix tenellus (Baker)
in California. Calif. Univ. Pubs., Ent. 5: 37-88,
illus.













COASTAL AMEAS


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VALLEYS IN COAST RANG

SIERRA N[VAOA ANRA


AMENTO


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WcNTEREY


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- - - J


Figure l.--Areas in central California which are
safe for the production of garden beet roots.





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