AGRICULTURAL EXPERIMENT STATION BENJ. IDE WHEELER, President COLLEGE OF AGRICULTURE thomas forsyth hunt, dean and director H. E. VAN NORMAN, Vice-Director and Dean University Farm School UNIVERSITY OF CALIFORNIA IE OF AGRIC BERKELEY CIRCULAR No. 134. (July, 1915) CONTROL OF RAISIN INSECTS. By Frederic T. Bioletti Introduction. Raisins, like other stored food products, are liable to attack from various insects, several of which, under favorable con- ditions, are capable of doing great damage. This damage is usually less common or noticeable in California than in the eastern states or other regions where the raisins are stored for a considerable time in the hands of distributors or retailers. This is because the bulk of the raisin crop in California usually passes from the field through the packing houses and into the hands of the buyer during the cooler part of the year, when the activities and reproductive powers of the insects are at their lowest ebb. When raisins are stored for many months even in California, and especially during the warmer part of the year, the insects may become very numerous and cause considerable losses. In packing houses, running continuously and receiving raisins from different sources, this is apt to occur. Certain measures are adopted by most of the packers in an effort to prevent this damage. The use of cleaning machines and fumigation with bisulfid of carbon are the chief among them. That these measures, as usually carried out, are not completely successful is shown by many samples of "wormy raisins" received at the Experiment Station, to- gether with complaints of the lack of efficiency of the control measures used. These complaints have been more numerous than usual during the last two years, indicating the advisability of an investigation of the trouble and of the causes of the failures in control. By the courtesy of a raisin-packing company, we were furnished with all necessary facilities for making this investigation, which was carried out by the Division of Viticulture with the advice and assist- ance of the Division of Entomology. In August, 1912, the work was placed in the hands of Mr. L. J. Nickels. Mr. Nickels made observations on the life history and habits of the principal injurious species and on the usual methods of control, and devised methods which gave promise of overcoming the trouble. That they have done so where applied is shown by the following 1— 1839G extract from a letter received on March 2, 1915, from the president of the company in whose packing houses the investigation was made : "Regarding the advice given by your department, following their investigations concerning the control of insect pests in raisins, I beg to say that we have followed this advice with marked success and have had no complaints whatever from goods to which the bisulfid process has been applied, though we have applied it to several hundred carloads all told, during the last two seasons." In order that other packers who fail to prevent completely the insect infestation of their raisins may be able to adopt more efficient methods this summary account is published. It is based on the observations and recommendations of Mr. Nickels so far as these appear to be of immediate practical interest. The figures and cuts were all prepared bv Mr. Nickels. Fig. 1. Raisin Worms. {Larva of Plodia.) NATURE OF THE INJURY. Raisins which have been stored for some time without special pre- cautions usually become "wormy." The so-called worms are the larvae, caterpillars or grubs of certain moths or beetles. The most common and troublesome of these is the Indian Meal Moth (see Fig. 2). This moth may be seen flying around and in raisin-packing houses. It lays its eggs on exposed raisins, especially on silk threads spun by the larvae. In the sweat boxes, the eggs are most numerous near the sides. On packed raisins, the eggs are deposited where cracks allow access. The larvae hatching from the eggs grow slowly to their full size of one-half to five-eighths of an inch in length (see Pig. 1). These "worms" vary in color from grayish white to shades of pink and green. When the larvae reach full size they enter the pupal stage. For this purpose they surround themselves with a network of silk threads to which pellets of excrement are often added. They remain in this resting condition for about sixteen days at an average summer tem- perature of 80 degrees Fahrenheit. The time is longer at lower tem- peratures, more than twice as long at 70 degrees Fahrenheit. It is probable that the insect passes the winter in this stage, but in warm situations the larvae may live over the winter. Fig. 2. Indian Meal Moth (adult). The adult or moth emerges from the pupa and lives on the average about one week. They are plentiful only in summer and autumn and do not breed in the winter. The Fig Moth is very similar in appearance and habits to the Indian Meal Moth. It has been found attacking raisins, but is much less abundant. Another insect, the Saw-toothed Grain Beetle, often causes "wormy" raisins, but is much less troublesome than the moth. The larvae or "worms" are yellowish white, slender and somewhat flattened (see Fig. 3). They are much smaller than the moth larvae, only about one-eighth of an inch long when full grown. They pupate in a delicate cocoon formed of fragments of their food and excrements. The adult is a small beetle about one-tenth of an inch long and about one-quarter as wide (see Fig. 4) . 2—18396 The adult beetles live much longer than the moths and are present throughout the year. Attention to the prevention of the increase and spread of this insect is therefore necessary at all seasons. Another beetle, the Bust red Flour Beetle, has been found in small numbers attacking raisins. Fig. 3. Saw-toothed Grain Beetle (Larva) SUGGESTIONS FOR CONTROL. The observations of Mr. Nickels indicate clearly that much can be done to diminish the damage due to insect attacks on raisins by slight modifications of the present practices in packing houses. They appear to show, moreover, that by somewhat greater modifications and the use of simple, inexpensive devices and measures, the infestation can be completely prevented until the raisins leave the hands of the packers. They can thus be delivered to the retailer in perfect condition and remain sound on his hands much longer than is at present usual. Complete protection under all conditions can be obtained, probably, only by the use of insect proof packages. Attempts have been made to devise such a package, but while some are promising, none has yet been demonstrated to be completely successful. The commencement of the infestation of a packing house is due to insects brought in on raisins from the vineyard or from other places where they have been stored. The insects brought in from the vineyard are comparatively few in number. The great abundance of insects in certain seasons is due partly to the accumulation of insects, due to the cleaning machinery, and partly to the multiplication of these insects in the packing house. The cleaning machinery removes nearly all the moths and beetles, in their various stages, from the raisins, but most of them are allowed to escape, to breed and to infest other raisins. The refuse of stems and inferior raisins allowed to accumulate in and around the packing house, and occasionally the stores of raisins allowed Fig. 4. The Saw-toothed Grain Beetle (adult). to stay in the packing house for weeks or months often favor the abundant multiplication of the insects collected by the cleaning machines. The first thing to be done, therefore, is to catch and destroy the insects removed by the machinery. This can be done to a great extent by a modification of the box used to catch the refuse. This refuse seems to be the principal source of reinfestation. In some cases, insects in large numbers have been observed leaving the refuse. Few insects apparently are injured by the cleaning machinery. Many of the small beetles reach even the cap stemmer and escape from its refuse box. To prevent this a simple trap has been devised. It consists of a movable frame, having on its under side a pad of cloth which is to be saturated with coal oil or crude carbolic acid. This pad extends beyond the inner edge of the box. It is protected from falling refuse. Insects cannot crawl out of the box. The frame is easily removable when it is desired to .empty the box. The cloth pad should be moistened often enough to exercise its full deterrent powers. The contents of the box should be burned. INSECT TRAP FOR REFUSE BOX. A section and perspective view of this box is shown in Fig. 5. B is the refuse box, A is a frame composed of four boards. This is to be made just large enough to slip over the outside of the box. From the top of this box-encircling frame, another set of four boards, B, is made to slope downward at an angle of 45 degrees and extend over the inner edge of the box. These boards should be at least six inches wide. All joints should be accurately fitted and the four corners should be reinforced with iron. Upon the under side of D is placed a pad of cloth, C, at least four inches wide, extending three or more inches beyond the inner edge of B. The inner edge of B should be beveled to fit D. The frame A D C is not to be fastened to B, but merely rests upon it so as to be easily removed when the box is emptied. Other insects which escape or do not pass through the machinery may be caught in trap boxes containing a few refuse raisins. These boxes are placed in convenient places in various parts of the packing house. Wandering insects will take refuge in them and can be killed by fumigation or by burning. These boxes should be fumigated or disinfected with live steam at least once a month to prevent breeding, and the raisin bait removed. All refuse of stems and spoiled raisins in and around the packing house on which the insects could multiply should be cleaned up regu- larly and destroyed. This is especially necessary during the breeding season, which extends from about the middle of March to the middle of September. All refuse should be cleaned up immediately, if pos- sible, and in any case a complete cleaning up should take place once a week. These methods carried out carefully would in most cases so diminish the numbers of insects in the packing' house that fumigation of the packed raisins might often be unnecessary. More perfect control of the insects could be obtained by methods aiming at the complete prevention of multiplication in both vineyard and the packing house. A method suggested by Mr. Nickels and Professor Woodworth promises to accomplish this end very effectively. It is based principally on so arranging the storage of the raisins that the vineyards are kept free- from anything on which the insects could feed for a sufficient length of time to insure their death from starvation, and to keep the packing house free from anything on which they could breed long enough to insure their extermination on the death of the adults. This method, generally carried out, should, in connection with the other control measures, insure the raisins from all injury by either the raisin moth or beetle. By the first of May, all raisins should be removed from the vineyard to the packing house. There will then be nothing in the vineyard on which the insects could feed or breed. When the new crop is made, therefore, it will be clean, as there is nothing to infest it with, if care is taken not to put it in contact with dirty sweat boxes or other infested material. When the new crop goes into the packing house, the methods already recommended will prevent any infestation during the first part of the packing season. During the months of October, December and January, there is rarely any emergence of adult insects or increase of larvae and the raisins may be stored either in the packing house or in the vineyard, except when the packing house is heated, in which case they should be held outside where the temperature is low. About February 1st, however, the packing house should be clear of all stored raisins and a thorough annual cleaning up would be advisable. During February, March and April, the packing house should be kept as free from raisins as possible, only enough being accepted as is necessary for current needs. No raisins should be kept in the packing house longer than four days during these three months. This will insure the removal by the cleaning process and the destruction before hatching of all eggs that may be laid by any adults which have survived the winter, or emerged from pupae remaining in the packing house or brought in from outside. All these adults will have died before the end of April, and, in May, any raisins remaining in the vineyards should be removed to the packing house. 8 FUMIGATION WITH CARBON-BISULFIDE. However carefully preventive measures are, carried out, raisins may occasionally become infested and curative measures will be necessary. Such measures are almost always necessary under ordinary conditions. All infestation can be destroyed by proper fumigation with carbon- bisulfide. This fumigation is perhaps best used as a measure of pre- caution in all cases where raisins are shipped. Carbon-bisulfide fumigation is in fact used in most packing houses, but often without satisfactory results, even in some cases with large amounts and prolonged treatment. Investigation showed that cases of failure were easily explained by a lack of a sufficiently air-tight fumigating room. Where there was any considerable leakage, 20 pounds of carbon-bisulfide per each 1,000 cubic feet was found insufficient. When the room was made thoroughly air-tight, 10 pounds was found to give perfect results if applied prop- erly. The boxes of raisins should be packed loosely and the carbon- bisulfide placed in shallow dishes near the ceiling. The room should be kept closed for at least twenty-four hours, for this time was found necessary to kill the beetles. The moths were killed in twelve hours and eggs in sixteen. In constructing a fumigating room, air-tightness, non-inflammability, and convenience should be considered. The fumigating rooms should be located so that both unstemmed raisins and the packed product may be readily trucked to them for treatment. Fumigation chambers should not be located close to railroad tracks nor boiler rooms. Construction of Fumigating Boom. Concrete is the only material which can be recommended for the construction of fumigating rooms. Where several tons of raisins are packed a day, two rooms are necessary. The doors of the fumigating rooms should open away from the packing house and swing towards each other. A letter from Mr. E. F. Mohrhardt, secretary of the Fire Under- writers of the Pacific, contains valuable suggestions to the prospective builder. (Copy.) Board of Underwriters of the Pacific, 814 Merchants Exchange Building, San Francisco, December 12, 1913. Mr. Leslie J. Nickels, Department of Entomology, Berkeley, Cal. Dear Sir : Your favor of the 10th is received, expressing your desire for information regarding the best construction of fumigating rooms in which carbon bi-sulfide may be used, in order to properly inform the raisin packers of the state. Our experience in this connection, as a result of the investigation of the engineering department of the board, is that fumigating rooms z ~C3F~ 10 inside packing houses should be strongly opposed; no method of con- struction can remove the danger. We have made an overhead charge of 1 per cent to the rate of insur- ance, and where these rooms have been maintained in the packing house the increase in rate has practically eliminated them therefrom. Should it be the intention to have such rooms in the packing plant, they should be constructed preferably of concrete, with door opening outside, and so arranged that an explosion would act through the door to the open air. Construction of wood with tar paper, or of wood with wire lath and cement finish, should not be advocated. I might add that the addition to rate above quoted is applicable to buildings of all classes of construction. Trusting the information given may prove of value to you, Yours truly, (Signed) E. F. Mohrhardt, Secretary. The Board of Fire Underwriters will gladly furnish any information at their disposal in regard to the construction of fumigating rooms. A room, twenty feet long, fourteen feet wide and seven feet high, will hold about ten tons of raisins. With any other length and breadth, the height of the room should not be increased. No windows or lights should be in the room. The door should be thick and constructed with beveled edges padded to prevent the escape of gas. The door of a fumigating room should be constructed like the door of an ice-chest. It should be not less than four and one-half feet wide in the narrowest part and six and one-half feet high. It should be lined with some gas-tight, fire proof material; sheet asbestos is very good. Top and sides of the door should be beveled and padded with canvas. The door should be painted, swung with very substantial hinges and fastened with an ice-box latch. Provision should be made for locking the door during periods of fumigation. Since trucks must pass in and out through the door, a beveled sill would be difficult to cross and furthermore would soon be destroyed. A method of making the door tight is shown in Fig. 6. On the floor near the bottom of the door A is placed a movable bar C which is held in place by the stationary blocks B B. Two or four sides of the bar may be padded with canvas. The bar is placed so that canvas comes next to the floor and door. As the door A is closed, the wedges D, fastened upon A, one braced by E, force the padded bar C to the floor and in turn (A) closing upon C (padded portion) makes a gas-tight junction. When the door (A) is opened and the bar C removed, passage in and out is not obstructed. The Amount of Carbon Bisulfide to Use. As a rule, fumigate raisins before packing. Use ten pounds of carbon bisulfide to every one thou- sand cubic feet of space to be fumigated. No allowance should be 11 made in the quantity of bisulfide used according to whether the fumi- gating chamber is full of raisins or not. As low as only 25 per cent of the available air space may be occupied by solid material when the chamber is full of raisins in sweat boxes. The bisulfide should be placed in shallow dishes upon the top of the raisins. Use as many dishes as possible. Continue the fumigation twenty-four hours. Save any remaining carbon bisulfide. This dosage was found to kill all stages of the insects found at Fresno in sweat boxes ; also in fifty-pound bulk boxes pressed and packed without paper, providing there were cracks in the covers of these boxes, at least one- sixteenth of an inch wide. Insects were placed amongst raisins packed loose in cartons, the cartons were nailed up in boxes. Slight cracks occurred along the edges of these boxes. They were placed so that the longest dimension of the cartons extended horizontally. With the above dosage all forms of life in the cartons were killed. Thompson Seedless was the only variety of raisins treated, but there is no reason to believe that the method of fumigation adopted would prove less successful with other varieties. STATION PUBLICATIONS AVAILABLE FOR DISTRIBUTION. Appendix to Viticultural REPORTS 1897. Resistant Vines, their Selection, Adaptation, and Grafting. Report for 1896. 1902. Report of the Agricultural Experiment Station for 1898-1901. 1908. Report of the Agricultural Experiment Station for 1901-03. 1904. Twenty-second Report of the Agricultural Experiment Station for 1903-04. 1914. Report of the College of Agriculture and the Agricultural Experiment Station, July, 1913- June, 1914. BULLETINS. No. 168. Observations on Some Vine Diseases in Sonoma County. 169. Tolerance of the Sugar Beet for Alkali. 170. Studies in Grasshopper Control. 174. A New Wine-Cooling Machine. 177. A New Method of Making Dry Red Wine. 178. Mosquito Control. 182. Analysis of Paris Green and Lead Arsenate. Proposed Insecticide Law. 183. The California Tussock-Moth. 184. Report of the Plant Pathologist to July 1, 1906. 185. Report of Progress in Cereal Investi- gations. 195. The California Grape Root-worm. 197. Grape Culture in California; Improved Methods of Wine-making; Yeast from California Grapes. 198. The Grape Leaf-Hopper. 203. Report of the Plant Pathologist to July 1, 1909. 207. The Control of the Argentine Ant. 208. The Late Blight of Celery. 211. How to Increase the Yield of Wheat in California. 212. California White Wheats. No. 213. 216. 220. 225. 227. 230. 234. 241. 242. 243. 244. 246. 248. 249. 250. 251. 252. 253. 254. 255. The Principles of Wine-making. A Progress Report upon Soil and Climatic Factors Influencing the Composition of Wheat. Dosage Tables. Tolerance of Eucalyptus for Alkali. Grape Vinegar. Enological Investigations. Red Spiders and Mites of Citrus Trees. Vine Pruning in California. Part I. Humus in California Soils. The Intradermal Test for Tuberculosis in Cattle and Hogs. Utilization of Waste Oranges. Vine Pruning in California. Part LT. The Economic Value of Pacific Coast Kelps . Stock Poisoning Plants of California. The Loquat. Utilization of the Nitrogen and Or- ganic Matter in Septic and Lmhoff Tank Sludges. Deterioration of Lumber. Irrigation and Soil Conditions in the Sierra Nevada Foothills, California. The Avocado in California. The Citricola Scale. CIRCULARS. No. 65. The California Insecticide Law. 69. The Extermination of Morning-Glory. 70. Observations on the Status of Corn Growing in California. 76. Hot Room Callusing. 79. List of Insecticide Dealers. 80. Boys' and Girls' Clubs. 82. The Common Ground Squirrels of California. 83. Potato Growing Clubs. 87. Alfalfa. 8S. Advantages to the Breeder in Testing his Pure-bred Cows for the Register of Merit. 91. Disinfection on the Farm. 92. Infectious Abortion and Sterility in Cows. 100. Pruning Frosted Citrus Trees. 101. Codling Moth Control in the Sacra- mento Valley. 106. Directions for using Anti-Hog Cholera Serum. 107. Spraying Walnut Trees for Blight and Aphis Control. 108. Grape Juice. No. 109. 110. 111. 113. 114. 115. 117. 118. 119. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. Community or Local Extension Work by the High School Agricultural De- partment. Green Manuring in California. The Use of Lime and Gypsum on Cali- fornia Soils. Correspondence Courses in Agriculture. Increasing the Duty of Water. Grafting Vinifera Vineyards. The Selection and Cost of a Small Pumping Plant. The County Farm Bureau. Winery Directions. Some Things the Prospective Settler Should Know. The Management of Strawberry Soils in Pajaro Valley. Fundamental Principles of Co-opera- tion in Agriculture. Alfalfa Silage for Fattening Steers. Aphids on Grain and Cantaloupes. Spraying for the Grape Leaf-Hopper. House Fumigation. Insecticide Formulas. The Control of Citrus Insects. Cabbage Growing in California.