The Pink Bollworm

L. F. Curl, R. W. White.

The pink bollworm first appeared in the United States in 1917 near Hearne, Robertson County, Tex.

The first published record of the pest was in a report in 1842 by W. W. Saunders, of the Entomological Society of London, who received specimens from cotton plantations in India. It has since spread over most of the cotton-producing countries. Severe depredations were reported in 1904 in what was then German East Africa. The pink bollworm is believed to have been introduced into Egypt from India about 1906 or 1907. It was found in 1909 in the Hawaiian Islands, where it caused such severe damage that cotton production was abandoned.

Cotton is grown commercially in 60 or 65 countries, 8 of which the United States, India, China, the Soviet Union, Egypt, Brazil, Mexico, and Argentina produce more than nine-tenths of the world crop. The pink bollworm is said to be generally established in all of them except the United States and Mexico. The losses of cotton it has caused have averaged 15 to 25 percent in India and Egypt. In China it has caused greater losses than all other Cotton insects together. In 1933 it was so bad in Russia that Russian entomologists came to the United States to study methods of control. An average annual loss of 20 to 25 percent is reported in Brazil, with a high point of 60 to 70 percent in the 1949-50 cotton crop.

The pink bollworm was brought into Mexico in 1911, and an average loss in yield in the Laguna region of 15 to 20 percent can be attributed to it. It reached the United States in infested cottonseed moved from the Laguna to some oil mills in Texas and soon thereafter it was found in nearby cotton fields. The commercial damage in the following 35 years has been negligible because vigorous measures were adopted immediately first, an effort to eradicate it and later, when that was found to be an impossible goal, a program designed to suppress infestation and prevent its spread. Despite the low intensity of infestation in most of the affected areas, however, the pink bollworm has inflicted heavy damage in certain localities and on individual farms. Fields in Presidio County, Tex., suffered total damage in 1931, for example, and in 1939 several thousand acres in Cameron County, Tex., suffered commercial loss.

In 1943 a number of fields in southwestern Louisiana showed 25 to 30 percent damage to the bolls from pink bollworm attack. In 1950 in a 400-acre field in Nueces County, Tex., 54 percent of the bolls had been made non-pickable by the pink bollworm. Others showed damage from 30 to 40 percent, and all bolls in one small field of late cotton were completely ruined by the pink bollworm.

Quarantines and control measures were in effect in 1951 in five States Arizona, New Mexico, Oklahoma, Texas, and Louisiana because of earlier findings there of the pink bollworm. It also occurs in wild cotton and dooryard cotton plants in southern Florida.

THE ADULT of the pink bollworm is a small brown moth about four-fifths of an inch from tip to tip of the extended wings. By day the moths are inactive and are seldom seen even in a heavily infested field. The female moth begins laying eggs a day or two after she emerges and continues for 4 or 5 days or longer. The moths normally live only 10 days or so.

The eggs are small, white, and oval and have a finely wrinkled surface. A moth usually produces about 200 eggs; most of them are deposited on the base of maturing green bolls under the calyx. Early in the season, in the absence of the favored boll, or later, after a saturated infestation has been reached in bolls, eggs are often deposited on the squares. The eggs hatch within 4 or 5 days in the summer, and the tiny larvae bore into the boll or square.

The newly hatched larva is glossy white, has a dark brown head, and bears but little resemblance to the full-grown worm. The mature larva is about one-half inch long. Rather wide, splotchy stripes of a deep pink give it a pink appearance. Larvae of the summer broods usually complete their growth in 8 to 12 days. In the summer most of them cut holes through which they leave the boll, dropping to the ground to pupate in the surface trash or cracks in the soil. Pupation may occur within the boll in areas of considerable rainfall.

Resting-stage larvae, which are those going into natural or forced hibernation, act differently. Cool weather, lack of humidity, lack of food supply, or other unfavorable conditions may cause a large percentage of the larvae to go into this resting stage. This cycle, particularly if entered into late in the season after cold weather begins, ordinarily lasts until the following spring when cotton is again fruiting. Larvae have been known to remain in hibernation for more than 2 years. Extremely dry weather in late summer or early fall seems to cause more than the usual number of larvae to enter this stage. If the dry weather is followed by considerable rain, many of the inactive larvae go into pupation and emerge as moths. This trait is a factor in control the cotton stalks are destroyed soon after harvest so that those moths will find nothing upon which to deposit their eggs when they emerge.

The pupal stage lasts 8 to 10 days in the summer, but is usually longer in the cooler weather of spring and fall. The pupa is whitish, with faint markings of pink when first formed; it turns to a mahogany brown as it dries and to a darker brown before emergence. It is about one-fourth inch long. It is covered with velvety hairs; practically no other pupae of similar size have such a pronounced pubescence. The hind end of the pupa is short, stout, hooklike, and up-pointing.

Under the best conditions during the summer breeding season, the pink bollworm can complete its life cycle in 22 or 23 days. In areas with long growing seasons, seven or eight generations are possible in a single season. The average number of generations in most of the cotton-producing areas of the United States is four or five if there are no cultural controls such as shortening of the season through a mandatory planting period and the destruction of stalks to stop breeding of the insects.

THE PINK BOLLWORM affects the cotton yield in several ways. In severe infestations, damaged squares and small bolls may be shed, leaving no visible evidence of reduced yield on the plant itself. The preferred food of the larva is the kernel of the seed. Usually the tiny larva, upon entering a boll, travels a short distance just under the inner surface of the covering, making a typical path commonly referred to as a mine. It soon leaves the lining of the boll and cuts through the immature lint to a seed. It devours the inside of the seed; then the small worm proceeds to the next seed, ruining the lint as it passes through it. Many larvae are heavy feeders and eat out all the seed of a lock or cell of the boll before they reach maturity.

If only one to three pink bollworms feed to maturity in a boll, several of the locks may escape damage; others may suffer partial damage but still be worth picking. In heavy infestations the entire boll may be so damaged that pickers leave it on the plant. Such damage is recognized readily, but partly damaged locks are picked. They lower the grade and staple of the lint because of the staining and cut fibers caused by the feeding of the worm as it passed from one seed to another.

There is also the added loss of oil content of the seed produced from heavily infested bolls. Hollowed-out seeds contain no oil. Naturally in extremely heavy infestation the greatest loss is the reduced yield of pickable cotton. Although the pink bollworm may completely ruin a boll, the damage is more clean-cut than the damage done by some other insects, such as the boll weevil. In passing from one lock to another, the larva usually cuts a round hole in the partition wall; the hole is easily recognized as the work of the pink bollworm.

AFTER FINDING the first infestation of pink bollworms in Texas in 1917, a zone in which no cotton could be grown was established in 1918, 1919, and 1920 for a short distance around the known infested spot. A regulated area of much greater size was established around the noncotton zone. The entire section was declared free of infestation and all controls were removed following inspection in 1923.

Later in 1917 infestation was found in other Texas counties Galveston, Fort Bend, Brazoria, Harris, Chambers, Liberty, Hardin, Jefferson, Newton, Jasper, and Orange. Cotton production was not extensive there. Noncotton zones, field clean-up, and regulatory measures were invoked in an effort to eradicate the pest. Inspections were negative from 1921 through 1926, and all restrictions were removed in 1927. Reinfestation occurred in 1943 in Liberty, Chambers, and adjacent counties, but was eradicated by enforcement of a small noncotton zone and a larger regulated area. The area was again released from quarantine in 1947. Brazoria, Chambers, Fort Bend, and Liberty Counties became infested again in 1950, and Harris County in 1951.

The pink bollworm was found in several southwestern parishes in Louisiana in February 1920, but was wiped out by setting up a noncotton zone and a regulated area. Inspections through 1924 showed no infestation, and all restrictions were removed.

Reinfestation occurred there again in 1943 but was eliminated and the area was released from quarantine after inspection of the 1946 crop. Unfortunately the tremendous spread of the pink bollworm during the 1950 crop season involved southwestern Louisiana for the third time, and vigorous counter measures were initiated.

The Shreveport area of Louisiana became infested in the fall of 1920 because of movement of seed from southwestern Louisiana before discovery of infestation there. Through a noncotton zone, regulatory, and clean-up measures, the infestation was eradicated. All restrictions were removed after negative inspections in 1925.

Infestations were found in Ellis and Grayson Counties, Tex., in 1921; each resulting from movement of cottonseed from Carlsbad, N. Mex., before an infestation was detected. Field cleanup, noncotton zones, and regulated zones were used to end the infestations. The quarantine was removed in 1926.

An infestation in the Salt River Valley of Arizona was found near Gilbert in Maricopa County in October 1929. Later in the season infestation was found in a cotton field in Pinal County. One of the largest non-cotton zones ever established was set up in Arizona to aid in eradication, and all of the Salt River Valley was placed under regulation. After several years of negative inspection, the quarantine was removed in 1934. Infestation reappeared in the late fall of 1938. A vigorous eradication program, involving field clean-up and heavy frequent applications of insecticide, was inaugurated in 1947, following a heavy build-up in a limited area in 1946. Inspections were negative during the 1947, 1948, and 1949 crop seasons. The area was released from quarantine for a second time on January 10, 1950.

Inspections were negative in 1951 in Arizona except in Cochise, Greenlee, and Graham Counties. This resulted in release from quarantine of additional Arizona counties of Pima and Santa Cruz early in 1952.