Khapra Control preliminary results of tests with fumigants c promise of effective treatments against dest

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tire grains but can feed on broken length and is enclosed, with the excep- kernels damaged by fourth instar larvae tion of a portion of the dorsum, by the or on the floury debris which they last cast larval skin. create. When the adults emerge from the Khapra larvae and adults on pecan meats. The adults, as a rule, do not feed, but pupa, they remain quiescent within the they have been observed gnawing at the last larval skin for a period which varies The State of California, by Quaran- from a few hours to 10 days or more, ac- tine Regulation 21, effective January 12, cording to temperature. The adult is a 1955, prohibits the removal from prop- small beetle, the female measuring about erty infested with the Khapra beetle- %’’ in length. It is a dark-brown, slow- granarium, Everts-of all moving . The adults do not fly, materials that might help the spread of and this insect can be dispersed by wind, this insect which is so destructive to birds, and so forth. stored grain and grain products. The presence of the Khapra beetle in Since the Khapra beetle was first grain causes heating, as was indicated found established in the United States in Imperial Valley when the outside air in stored in two warehouses in temperature was 53F and the tempera- Tulare County-November 1953-infes- ture of infested stored barley 12“ below tations have been discovered in eight the surface was 104F. additional California counties. Observations indicate that the Khapra After the insect was found in Tulare beetle remains active throughout the County, United States Department of year in Imperial Valley. Larvae col- Agriculture entomologists made a sur- lected at intervals during the winter vey of grain warehouses in the 11 west- Khapra larvae an walnut meats. from infested warehouses, taken to the ern states and uncovered other infesta- laboratory, and placed in a 90F tem- tions in Fresno, Imperial, Kern, Kings, perature cabinet completed their life Riverside, and San Diego counties of surface of grains which have al- cycle and became adults in a relatively California; in Maricopa, Mohave, Pima, ready been eroded by the larvae. short time. This would indicate that Pinal, and Yuma counties of Arizona; The Khapra beetle tends to confine its and in Curry and Roosevelt counties of activity to the top 2‘ of grain, but it New Mexico. has been found to penetrate to depths ef It is not known how the Khapra beetle 9’. Although reported losses vary from was introduced into this country, but 270 to 78%, an infested lot of grain, if the United States Department of Agri- left undisturbed, would eventually be a culture is proposing a quarantine to help complete loss. prevent the movement of the insect into In infested bagged material, the larvae uninfested areas. The quarantine, if weaken the sacks to the extent that ulti- warranted, would prohibit or restrict mately they tear. movement from the three states-or from infested areas within the states- Description of grain, grain products, dried seeds, of field and vegetable crops, bags and bag- The egg of the Khapra beetle is a ging, dried milk, dried blood, fish meal, little under 1/64” in length, narrowly meat scraps, and other items that might cylindrical, rounded at one end, some- help spread the beetle. what pointed at the other, and is a trans- lucent white when laid. The eggs are Khapra larvae an egg noodles. usually laid singly and often loosely in Nature of Injury the grain, but occasionally when they The larvae of the Khapra beetle feed are laid in the groove or furrow of a these , under the conditions ob- on a wide variety of stored products and wheat grain, several may be deposited served, do not hibernate. by their continual gnawing reduce the together. Under laboratory conditions, cultures material to a powdery mass. The fourth The newly hatched larva is about ?&” held at 93-95F, at either 100% light or instar-stage of growth-larvae attack in length and is yellowish-white in color. 100% darkness, have completed six gen- grain by gnawing at various parts of the The mature larva is about %” in length, erations since June 1953. At 90F, in kernel, and usually begin their attack is brownish-white in color, the body be- 100% darkness, or a combination of at some weak place in the pericarp, or ing covered with bundles of long, red- 50% darkness and 50% light, eight gen- seed coat. The first, second, and third dish-brown hairs. erations have been completed since May instar larvae are unable.to feed on en- The pupa is approximately 1J25” in 1954. These experiments indicate that

8 CALIFORNIA AGRICULTURE, M ARCH, 1955 survived a 28-day exposure at 24-43?, and some larae survived a four-hour ex- Studies posure at -5.8F. Preliminary results in- dicate that the pupae are more suscep- tible to cold temperatures than are the nd dust give larvae. Larval survival has been obtained fol- 'uctive pest lowing a six-hour exposure at 120F. Larvae kept in cultures and exposed to an outside temperature became active dgren, 1. E. Vincent, and H. E. Krohne during the warmer part of the day, al- though the temperature dropped to as Average life History in Days of Individuol Khapra Reared at Various lempera- low as 34F at night. turer. Larvae placed at 90F are continuing to survive after 160 days without food. lemperotureF Egg larva Pup0 to~~uI+ Other workers have found that the Khapra larvae in almonds. 70 13 161 19 193 Khapra beetle larvae will survive for as 80 8 153 10 171 long as three years without food. 90 5 27 6 38 were the most resistant to hydrocyanic 93-95 3 19 4 26 acid and ethylene dibromide. Preliminary results of fumigation tests conducted at 70F, with a two-hour the light and temperature combinations exposure on eggs, larvae, and pupae of tested had no effect on insect develop- the Khapra beetle, indicate that the eggs ment or egg laying. are the most susceptible stage to fumiga- The average total number of days re- tion by hydrocyanic acid, acrylonitrile, quired from egg to adult for the Khapra ethylene dibromide, methyl bromide, beetle, when reared as individuals, was and ethylene chlorobromide. Of the ten 193 at 70F, 171 at %OF, 38 at 90F, and fumigants tested hydrocyanic acid, acry- 26 at 93-95F. The critical temperature lonitrile, chloropicrin, ethylene di- appears to be somewhere between %OF bromide and methyl bromide are the and 90F, as the life cycle is very much most toxic fumigants to egg, larval, and shortened in this interval. This corre- pupal stages of the Khapra beetle. sponds to other data, which indicate that Preliminary results with malathion this insect is a much more serious pest used at the rate of 4, 8, 12, and 16 parts in warmer climates. per million on wheat of 97% moisture During its larval stage, the Khapra Khapra larvae on spaghetti. content appeared to control this insect beetle may molt anywhere from two to effectively. The residual action of mala- nine times, depending on the tempera- Various foods being tested to deter- thion depends on the concentration used ture, although under adverse condi- and the moisture content of the grain. tions, it may molt as many as 15 times. mine whether the Khapra beetle can de- velop on them include raisins, walnut- Tests are being conducted in coopera- pecan-almond meats, spaghetti, egg tion with the State of California Depart- noodles, prunes, dried peaches, pearl ment of Agriculture to determine the barley, tapioca, dried beans, flax, pow- effect of various fumigants on seed dered beef blood, various grains, dog germination. food, and skim milk. Although these D. L. Lindgren is Entomologist, University tests have not been concluded, it is evi- of California, Riverside. dent that the materials vary greatly in L. E. Vincent is Principal Laboratory Tech- susceptibility to attack. The develop- nician, University of California, Riverside. mental period was shortest on wheat, H. E. Krohne is Laboratory Technician, Uni- versity of California, Riverside. barley, dog food, and . Such ma- terials as raisins, prunes, and peaches FUMIGATION TESTS were fed on, but no adults have been Milligrams per liter to Kill 95% at 70F with a observed. 2-Hour Exposure Con- Khapra fused Oron- Beetle Flour Ory Control Studies Beetle Weevil larvoe Adults Adults Khapro larvae on dried prunes. A series of laboratory experiments were conducted to determine the relative Hydrocyanic acid . . 7.8 2.2 29.0 susceptibility of naked Khapra beetle Acrylonitrile ...... 18.0 11.0 8.0 The average viable egg production at larvae, confused flour beetle adults- Ethylene dibromide ...... 27.0 21.0 29.0 90F was 93 and at 70F was 65, indicat- Tribolium confusum-and granary wee- Chloropicrin ...... 34.0 31.0 34.5 ing the higher temperature to be closer vil adults-Sitophilus granarius-to ten Methyl bromide . . . 54.0 44.0 27.0 to the optimum for the development of different fumigants. Results of these tests Ethylenechlorobromide . . 110.0 26.5 48.0 this insect. are shown in the table at the lower right. Methallyl The adults were found to live from The Khapra beetle larvae were more chloride ...... 135.0 75.0 87.0 three to 47 days, depending on tempera- resistant than the other two insects Carbon bisulphide ...... 215.0 >179.0 149.0 ture. tested to all fumigants, with the excep- Ethylene A few eggs survived a two-hour ex- tion of hydrocyanic acid and ethylene dichloride ...... >271 .O 226.0 271.0 posure at -5.8F. The majority of larvae dibromide. The granary weevil adults Ethylene oxide . . . .> 48.0 > 40.0 31.0

CALIFORN I A AGRICULTURE, MARCH, 1955 9