Cultural methods for controlling the cotton boll worm

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knowledge, policies, or practices

Hawaii Agricultural Experiment Station,
HONOLULU.

Bove WILCOX, Special Agent in Charge.

PRESS BULLETIN NO. 32.

CULTURAL METHODS FOR CONTROLLING
THE COTTON BOLL WORM.

BY

C. K. McCLELLAND, Agronomist
AND

C. A. SAHR, Assistant in Agronomy.

It is a matter of record that cotton culture has been attempted
in Hawaii upon several different occasions, but there can be no
doubt but what the attempt that has been made in the last few
years has been the largest and most systematic of any attempts
made. It seems to be that the profitableness of cotton culture is
going to depend largely upon the success that is obtained in con-
trolling insect pests. Cut worms, aphis, mealy bugs and others
at times cause considerable damage to the cotton plants, but the
one pest that does more damage than all others combined is the
small boll worm (Gelechia gossypiella). In fields where the
worm has been undisturbed, as high as 60 to 75 per cent of the
bolls have been infested by this boll worm, in which case the cot-
ton that may be picked from the field will not be sufficient to
pay any profit on the labor involved in producing the crop.

jd

In Bulletin No. 18 of this Station a detailed description of the
insect has been given and from this we take the life history
which 1s as follows:

The eggs are deposited singly upon squares, flowers or leaves—
from which in about ten days the larva or worm is hatched. The
larva feeds upon the plant for a period of about twenty-three
days, after which it pupates and emerges from the pupa as au
adult or moth fourteen days later. After a few days the moth
will begin egg-laying and lives for several days. The larva is
the form that does the damage to the cotton. It may attack the
squares or flowers and destroy the vital parts of the flower, in
which case the square or bloom falls to the ground. Scores of
squares from each plant in our Caravonica field fell to the ground
during the month of April as a result of insect attack. The larva
also attacks the young bolls in all stages of growth and usually
damages the lint and eats out the seed contents and causes a pre-
mature opening of the boll.

It has been our observation that Sea Island cotton is more sub-
ject to the attack of this worm than Caravonica and Egyptian
somewhat less subject, while upland cotton is the least subject
of all varieties to their attack. The worm is known to attack
other host plants and has been found in Milo (Thespesia pof-
ulnea), may possibly be found in Hau bushes and in India it 1s
said to attack trees which have oil-bearing seeds.

Because of its occurrence in large numbers only upon cotton
it will be possible in a measure to control it by cultural methods,
and, until an effective parasite is found, we must make the best
use possible of such methods. It must be remembered that these
additional measures add to the expense of cotton production and
so long as effective should be as simple as possible. However,
the pruning advocated being necessary for other reasons, only
the two others given should be considered extra.

Cultural methods include, first, annual pruning; second, clean
culture; third, trapping the mature moths. |

3

PRUNING.

By severely pruning the plants in the fall and burning all
branches and bolls immediately, large numbers of the insect in
different stages will be destroyed. If no other host plant offers
itself most of the insects that survive the fire stand great chance
of perishing before new food in the shape of squares, flowers
and bolls of cotton will be found in the following spring. It is
important that this work should be done in as short a time and
in as thorough a manner as possible when once started and
that all plants in the vicinity should be pruned. Ornamental
plants in yards, or hedges of cotton remaining, or any plants left
in the field, serve as breeding places for the insect in which they
are carried over for the next crop. This we learned to our sor-
row in carrying on a pruning experiment to determine at what
time it was best to prune. To secure best results in burning the
green branches, a good hot fire should be started with dry ma-
terial and the work of piling on the brush will be greatly facili-
tated if the fire is placed in a shallow hole or gulch near the cot-
ton field. In clearing land of guava or other bushes it would be
well to leave a part of these in the place where it is intended to
burn the cotton prunings.

Cotton Plant Properly Pruned.

5

Concerning pruning there is much _ yet to be learned,
whether it shall be done early or late, high or low, and for how
many years the plant will thrive under such treatment. All that
we know is that it is necessary to prune occasionally in order to
control the size and shape of the plants and to maintain the
quality of the lint. From experiments in 1911 we conclude that
with us fall pruning is imperative in order to allow proper de-
velopment of the plant during the winter months when moisture
is plentiful. Plants allowed to bear during this time, then
pruned about March first, made plants only about two-thirds as
large as those pruned December first. The increase in yield of
fall pruned plants was nearly 46 per cent, the average yield per
plant being 1.2 pounds and .82 pounds of lint per tree for fall
and spring prunings during the second year’s growth of the
plants.

PERCENTAGE OF BOLL WORM INFESTATION, 1911.

Caravonica Caravonica Sea Island
1-2 Acre 1-2 Acre 1 acre—new seeding.
Date of Cut back | Date of | Cut back | Date of |
Picking Dec. 5,1910| Picking. | Mar. 1, 1911 | picking. |
May 31 | 70.6 | | Aug. 22* | 3.9
June 9 49.5 Jan. 2847 195 [ee es cS
anes 26. fo 20.-b $68 +129 8.0
PSA 39.9 Feb. 8 23.6 | Sept. 2 Pee
July 5 14.9 OG 19.5 ris Heo Ore 23.
ences 9.8 14+ | 3.9
ae OY 11-8 | oe As tn Ee
eee | BO Gs
Aug. 2 9.5 Peter Gad | oe ee
etl St Ane 11". * |-/355 Oct. 7 | 45.2
= anepe e ro) METS by Oe ans 20 ree eg
eet 2 9.2 See 7a a aes iii |i fo er
st 5.0 Sepia @[2ises popes: 13.5
Sept. 8 6. ral PID Dib ase ol 2G ae few
eer tt 2.9 cy ted te Es Nove! i/o agg
aie 2. SaP SAD a Hye O |
He OBS 5.1 a SOL ey |
Oct. 10 4.3 Gels wil |
“99 i ee ae |

* First Picking. 7 Second. § Third.

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From this it will be seen that fall pruning is unquestionably
preferable. We have no conclusive ideas as to whether to prune
high or low, the high pruning in some cases excelling while
in other cases the low pruned plants gave the better yields. One
theory given is to prune very low at first and at each succeeding
season prune a few inches higher so as always to cut on new
growth. After several such treatments it may become necessary
to prune low again. Another plan is to cut high and low alter-
nately. However, the form of the individual plant and the con-
ditions under which it is grown, rather than any book rule, will
determine the treatment which that particular plant should have.
In 1911 the yield from all high pruned plots (four feet high:
slightly exceeded that from low pruned plots pruned two feet
high. These results were from Caravonica cotton.

With Sea Island cotton our experience has been that growth
starts low even upon high pruned plants so that low pruning be-
comes necessary. To control the size and shape of the plants
the pruning of Caravonica becomes more necessary than for other
varieties because of its rank growth, but in order to control the
boll worm the pruning of all varieties becomes necessary.

CLEAN CULTURE.

This consists in picking up and burning fallen squares when
known to contain the boll worm and, secondly, when picking the
cotton the pickers should carry an extra sack in which the in-
fested bolls should be put and carried to the side of the field
and later burned. This part of the fight against the boll worm is
in many cases very difficult to carry on since the laborers in the
field look upon it as just so much extra and unnecessary work,
but if any headway is to be made against the boll worm or if
any profit from the crop is expected some means should be taken
to get this work done by the cotton pickers. At the Station we
have also fumigated the seed cotton at the gin house with hy-
drocyanic acid gas but some of the worms seem to have sur-
vived this treatment.

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TRAPPING THE MATURE MOTHS.

The moths fly by night and many may be caught by traps. The
junior author of this bulletin has improvised a simple device
which is herewith illustrated and described. A post is set in the
ground, the post being of sufficient height to hold a lantern
above the plants so that the light may be seen for some distance.
A hole 1 1-2x6 inches is previously bored in the top of the post.
Into this a wooden pin (3), shaped as shown in the cut, ts fitted.
The top of the pin is so shaped as to receive a pan (4) which
may be made similar to an ordinary cake tin 2 or 3 inches deep
by 12 or 14 inches in diameter. When in position the pan con-
tains water with a coat of kerosene oil. After the pan is placed
over the pin a square piece of sheet iron (2) is screwed to the
pin to support the lantern. This square sheet of iron should
have sides of length equal to diameter of the base of lantern,
and should have three corners turned up and with a pin through
the fourth to hold the lantern securely. A lantern with larger
sized globe (1) is preferable since smaller globes get hot and
then break should there come a dash of rain. The trap as put
together and set up in the field is shown in the cut (5). The
moths fly towards this light and many of them fall into the pan
and are destroyed. Many more will be caught upon still nights
than upon windy nights. Where winds are prevalent, place
trap toward the leeward side of the field and where winds are
not prevalent, traps can be placed at equal intervals from each
other or in the center of small fields. Two, three or even one such
trap per acre will give good results. When one considers the
great egg-laying capacity of a single moth it is hard to over-
estimate the value of capturing 10 to 50 or more moths a night,
possibly per acre, if they are plentiful. By pruning partly in De-
cember and partly in March we commenced the picking season
of 1911 with 70 per cent of bolls infested as shown in the ac-
companying table, and then by fighting the insect according to
the methods given above we succeeded in controlling the situation
somewhat and in reducing the percentage of infestation as also
shown in the table.

Lantern Trap and Its Parts

Of course the percent of infested bolls in-the early pickings 1s
larger than the percent of the total number of bolls, since the
worm caused so many of the bolls to open prematurely. The
table also shows the greater liability to attack of the Sea Island
variety. During the season of 1912 we aim to get the benefit
of the annual pruning as described by doing the work all at one
time ; in which case we hope to have an easier fight than in 1911;
yet because of more or less ornamental cotton and milo in Hono-
lulu we can hardly hope to start clean. Upon one large plant-
ing where the pruning and burning was well done in 1910,—
we are informed that the infestation in the spring of 1911 was
very light; but, because of the difficulty to get the pickers to col-
lect infested bolls, the percentage of infestation greatly increased
during the season. This shows what can be accomplished by em-
ploying the first named method and we have demonstrated the
value of the second and third. Other host plants than cotton
must always be kept in mind and cut down and. burned; then if
the grower works faithfully along the lines mentioned above he
may hope for some returns for his labors.

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