TECHNICAL BULLETIN NO. 188 SEPTEMBER, 1930 UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D. C. LIFE HISTORY AND HABITS OF THE PLUM CURCULIO' IN THE GEORGIA PEACH BELT By OLIVER I. SNAPP Entomologist, Division of Deciduous Fruit Insects, Burean of Entomology . CONTENTS Page Introduction - - - 1 lÁíe history and habits of the plum curculio, as The Qeorgia peach belt and its climate 2 observed from 1921 to 1924, inclusive—Con. Methods and equipment 3 The egg 7 Studies of oviposition 3 The larva 27 Studies of incubation 3 The larva, pupa, and adult in the soil 37 Studies of the larval period 3 The adult 45 Larvae from peach drops 3 Time required for transformation from egg Studies of pupation 4 to adult 58 Emergence of adults 4 Occurrence of beetles in orchards through- Studies of parasites 4 out the seasons of 1921 to 1924, inclusive.. 60 Studies of hibernation -. 4 Relation of temperature to appearance of Results of jarring 5 plum curculios from hibernation 70 Studies of longevity 5 The relation of moisture and temperature Feeding tests 5 to the development of the curculio^..:._, 73 The insectary _ 6 Parasites of the plum curculio in Georgia 77 Weather records 6 Feeding tests with lead arsenate 80 Life history and habits of the plum curculio, as Conotracheliis anaglypticus as a peach i;)est 88 observed from 1921 to 1924, inclusive-^ 6 Summary..- .- 90 INTRODUCTION The plum curculio, Conotrachelus nenuphar Herbst, is the most important insect pest attacking the peach fruit in Georgia and presents one of the chief problems with which the peach growers of that State have to contend. Growers experienced an outbreak of this insect in uncontrollable numbers during the season of 1920, when it took a toll to the value of several million dollars. Only a small proportion of the peaches of the late varieties, which make up more than one- half of the acreage of peaches, could be marketed that year, the larvae of the curculio rendering the remainder unmerchantable. Much of the fruit that was shipped was unsalable when it arrived on the markets, because tiny larvae, hatched during harvest and too small to be detected when the fruit was packed, had become sizable in transit. This outbreak, unprecedented in the history of the insect, was largely due to carelessness and inadequate attempts at control in preceding years. The progeny of a number of ineffectively controlled generations of the curculio had been multiplying for several years, the result being the serious outbreak of 1920, when w^eather and other conditions were particularly favorable for the development of the insect. The seriousness of the situation led the Bureau of En- ' Conotrachelus nenuphar Herbst; order Coleóptera, family CurcuUonidae. U029e—30 1 2 TECHNICAL BULLETIN 188, U. S. DEFT. OF AGRICULTURE tomology, at the urgent request of peach growers in Georgia, to ■ undertake a thoroughgoing study of the Ufe history of the phim curcuho in the Georgia peach belt. These studies were conducted during the years 1921-1924 at Fort Valley, Ga., where a field laboratory had been estabhshed.^ THE GEORGIA PEACH BELT AND ITS CLIMATE One of the largest peach-growing districts in the United States is in central Georgia. This district surrounds Fort Valley, where the studies reported in this bulletin were conducted Within a radius of 100 miles of this town there are between 10,000,000 and 12,000,000 bearing and nonbearing peach trees in commercial orchards. The relief of the district varies from generally level, in the immediate vicinity of Fort Valley and to the southward, to rolling and hilly in the more northerly portions. The elevation ranges from 230 to 975 feet above sea level. The elevation where these studies were conducted is 526 feet. The climate of this district is characterized by long, hot summers, during which the changes in temperature from day to day are very small, and by mild, brief winters. The normal annual mean tempera- ture is about 66° F. High temperatures continue during June, July, and August, and occasionally September is the hottest month of the year. The average annual rainfall in the district is 48 inches.^ Climatic conditions greatly influence the development and severity of the curcuho in the Southeast. Table 1, presenting for the four years of the study the mean temperature and the precipitation at Fort Valley for the period from February to October, inclusive, the season of activity of the curculio in Georgia, is therefore included to show a comparison of the weather conditions that prevailed each year, and for correlation with the development of the curculio.'' TABLE 1.—Mean temperatures and precipitation, Fort Valley, Ga., February to October, 1921-1924 Month Mean Mean Mean Mean Precipi- Precipi- Precipi- tempera- Precipi- tempera- tation tempera- tation tempera- tation tation ture ture ture ture °F. Inches Inches 'F. Inches 'F. Inches February.-. 61.4 2.77 •M. 9 4.67 49.4 3.87 47.3 6.18 March 64.9 1.10 hi.O 9.73 ,67.8 7.51 62 6 3.37 April 64.4 3.10 68.0 2.63 64.4 3.27 63.6 4.79 May 71.0 3.80 72.5 6.90 69.-5 9.71 69.8 3.94 June 81.2 2.91 80 0 3.74 70.3 6.99 80.4 4.93 July 80.0 8.24 80.6 6.96 79.7 2 64 80.0 6 18 August 79.8 4.31 78.8 4.28 80.8 6.00 82 6 1.39 September. 82.4 1.80 77.2 2 63 77.0 2 83 71.7 11.25 October 64.8 2.21 66. S 2.91 6.6.3 .46 63.4 .81 Total preoipita- tionfor season. 41.28 Mean tempera- ture for sea- 71.1 70.9 67.9 Î The writer has been in charge of investigations of peach insects at the Fort Valley field laboratory since its establishment in November, 1920. The life-history records tor 1921 were taken by E. K. Selliregg, as- sisted by C. H. Brannon. The writer was assisted in taking the records for the other years by II. J. Harris and J. A. Dodd in 1922, by H. S. Adair in 1923, and by B. S. Brown, jr., in 1924. In addition, the writer is greatly indebted to A. L. Quaintance, in charge of deciduous-fruit insect investigations of the Bureau of Entomology, for valuable suggestions and advice given throughout the investigations, and to C. H. Alden, of the field laboratory at Fort Valley, for much assistance. 3 UNITED ST.\TES DEPARTMENT OF AGRICULTURE, WEATHER BUREAU, SUMMARY OF THE CLIMATOLOGI- GAL DATA FOR THE UNITED STATES BY SECTIONS. CENTRAL AND EASTERN GEORGIA. U. S. Dept. .'Vgr., Weather Bur. Bui. W, ed. 2, v. 3, illus. (Reprint Sec. 86.) 1926. * UNITED STATES DEPARTMENT OF AGRICULTURE, WEATHER BUREAU, CLIMATOLOGICAL DATA, GEORGIA SECTION . February to October, 1921,1922,1923, and 1924. Atlanta, Ga. 1921-24. PLUM CtTRCtTLIO IN THE GEORGIA PEACH BELT Ö METHODS AND EQUIPMENT The procedure in these studies of the plum curculio in Georgia was very similar to that followed by Quaintance and Jenne ° more than 15 years ago in their studies of this insect in several sections of the country. Much of the information resulting from the writer's studies is presented herewith in tables patterned after those of the investi- gators named. STUDIES OF OVIPOSITION Upon copulation, individual pairs of the insect were isolated and confined in separate jelly jars. These jars were supplied with egg- free peaches, which were renewed each day, the peaches removed being examined (pi. 1, A) with a binocular microscope to determine the number of eggs deposited by each female during the previous 24-hour period. The eggs can be located readily with the aid of a dissecting needle, used to throw up the excavation made in the peach by the female when the egg is deposited. Several inches of sand, which was kept damp, were placed in the bottom of each jar, and the jars were supplied daily with fresh peach-tree foliage for food and pro- tection. STUDIES OF INCUBATION All of the peaches containing eggs deposited by a paired female during each 24-hour period were placed together in incubation jars. These peaches were then examined under the binocular each day or twice a day to determine the incubation period of each egg. STUDIES OP THE LARVAL PERIOD The peaches containing eggs, for which incubation records had been taken, were placed in wire trays, fitted within glass battery jars 6 by 8 inches in size for observation on the larval feeding period. As the larvae became full-grown and left the fruit, they fell through the wire tray to the bottom of the battery jar where they were collected daily, and records were made on the length of time spent in the larval stage. LARVAE FROM PEACH DROPS In order to obtain additional material for the life-history studies, peach "drops" were collected each year from under trees in the com- mercial orchards, for curculio larvae. These drops were placed in frames with wire bottoms, under which were slides consisting of cloth fastened to wooden frames. As the larvae reached maturity and left the fruit they fell through the wire bottom to the cloth slide below. The slides were pulled out each morning and the larvae counted and removed. These frames were also used in studies to determine the curculio infectation of peach drops from various orchards, and from the same orchard, from year to year, for purposes of comparison.