Laboratory Evaluation of Food Baits for their Relative Ability to Retain Three Species of Stored-Product

Beetles (Coleoptera)l

Bh. Subramanyam2, V. F. Wright", and E. E. Fleming"

Department of Entomology ({ansas State Universit.y

Manhattan, Kansas 66506

J. Agric. Enlomol. 9(2):117-127 (April 1992)

ABSTRACT The effectiveness of freshly cracked grains (corn, wheat, and sorghum), rolled oats, and kibbled carobs in retaining adults oflhe flat grain beetle. Cryptolestes pusillus (Schon herr), red nour beetle, Tribolium castaneum. (Herbst), and rice weevil, Sitophilus oryzae (L.), was evaluated in the laboratory. Cracked grains were also compared with a food·haiL mixture (cracked corn and wheat, roBed oats, and kibbled carobs; 1:1:1:0.2 parts by weighO. currently used for detecting stored-product beetles on farms and in country elevators in Kansas. Choice lests were performed in 41.5-cm diam wooden arenas using 5 g of one or more food materials in LoLaI darkness at 27°C and 45% RH. Each insect species was tested separately, and 80 adults of each species were exposed to the foods for 24 h. The number of adults retained in the foods was recorded. In two separate tests, the numbers of C. pusillus "ctained in cracked grains and rolled oats, and in cracked grains and food·bait mixture were not significantly different. Similar results wcrc observcd with T. castaneum. However, significantly more S. oryzae adults were retained in cracked com and wheat than in cracked sorghum. Also, the numbers of S. oryzae retained in cracked corn, crncked wheat, and food-bait mixture were not significantly diflcrent. Kibbled carobs retained significantly fewer adults of all three species compared with cracked grains. The numbers of C. pusillus or T. caslaneum retained were not significantly different in food-bait mixture with and without the carobs. However, significantly more (lA-fold) S. oryzae adults were retained in food-bait mixture with carobs than without carobs. These findings suggest that any of the cracked grains or rolled oats could be used as bait for detecting adults of C. pusillus or T. caslal1ew1l, whereas cracked com or cracked wheat could be used for detecting S. oryzae ndults. The cracked grains can be potentially substituted for the cUlTently used food-bait mixture. The pCI'formance of these cracked grains in detecting adults of the three insect species in the field remains to be tested.

KEY WORDS Rice weevil, nat grain beetlc, red nour bcetle, detection, Coleoptera, Curculionidae, Tenebrionidae, Cucujidae.

~ RCi:ei\'cd for publication I April 1991; accepted 16 October 1991. J Department of Entomolob'Y, Universit.y of Minnesota, St. Paul, MinncSOLn 55108.

International Seed and Grain Science Center, Escuela Agricola Panamericana, Box 93, Tegucigalpa, Honduras.

~ 804 NE 2nd Street., Corvallis. OR 97330.

117

118 J. Agric. Entomol. Vol. 9, No.2 (1992)

Residual populations of stored-product insect species, especially adults of beetles, seek refuge in cracks and crevices of grain stores and warehouses. Because of their harborage-seeking behavior, the activity of these insects is dif­ficult to detect visually unless populations reach high levels. However, detection of residual populations is possible with the use of traps baited with food attrac­tants or pheromones. Early detection of insects with food attractants, pheromones, or combinations of food attractants and pheromones may be impor­tant in quarantine 01' management programs (Barak 1989).

Food attractants have been successfully used for detecting adults and larvae of several stored-product insects (Strong 1970, Nara et a1. 1981, Barak and Burkholder 1984, Barak 1989). The food attractants, especially those that are liquids at room temperatures (e.g., wheat germ aiD, have been used in corrugat­ed paper traps for capturing adults and larvae of several insect species (see Barak and Burkholder 1984, Barak 1989). The oil in a pitfall-type device in food-baited traps not only attracts insects but also kills trapped insects by suffo­cation.

Barrer (1983) experimentally showed that the odor emanating from bulk­stored whole wheat grains was responsible for attracting a variety of stored­product insects. The olfactory responses of adults of stored-product insects to solvent extracts of cereal grains, rolled oats (Ohsawa et al. 1970, Pierce et al. 1981) and kibbled carobs (O'Donnell et al. 1983), and larvae of the khapra bee­tle, Trogoderma granarium Everts to oat, corn, and wheat germ solvent extracts (Barak 1989), suggest that volatiles in the foods are responsible for attracting insects. The attractiveness of cracked grains and kibbled carobs to insects is attributed to these volatiles released upon cracking or crushing. Walgenbach et al. (1987) and Trematerra and Girgenti (1989) have shown that two to three times more adults of Sitophilus spp. were attracted to cracked grains than to whole grains.

Several researchers (McFarlane and Warui 1973, Pin niger 1975, Pinniger et al. 1984, Hodges et a!. 1985) have used whole or crushed cereal grains, legumes, and kibbled carobs as bait for detecting various stored-product insect species. Pinniger (1975) used 80 g of equal parts of wheat, broken peanuts, and crushed carobs in a plastic-mesh envelope, and detected about 40 insect species in grain stores (Pin niger et a1 1984). Using whole and cracked corn and coffee beans, McFarlane and Warni (1973) detected 10 species of beeties in cargo ships and dock-side transit sheds. Hodges et al. (1985) used milled brown rice in a plastic-mesh envelope for detecting and assessing populations of nine insect species infesting a rice store. V. F. \\Tright (unpublished data) used a mixture of foods (cracked corn and wheat, rolled oats, and kibbled carobs; 1:1:1:0.2 parts by wt; total wt = 177 g), as bait in a wire-mesh envelope. This food-bait mixture was useful in detecting and monitoring several species of economically impor­tant stored product Coleoptera on farms and in country elevators in Kansas. However, unlike liquid food attractants in corrugated paper traps, dry food baits used in envelopes do not trap insects. Hence, the effectiveness of these dry food baits in detecting insects depends not only in attracting insects to the food source, but also in aggregating and retaining insects once they contact the food.

[0 the present investigation, freshly cracked corn, wheat and sorghum, rolled oats, and kibbled carobs were evaluated in the laboratory via choice tests for

119 SUBRAMANYAM ct al.: Detection or Stored-Product Beetles

their ability to retain adults of the nat grain beetle, Cryptolestes pusillus (Schonherr); red nour beetle, Tribolium castaneum (Herbst); and rice weevil, Sitophilus oryzae (L.J. In addition, the cracked grains were compared with the food-bait mixture used by V. F. Wright (unpublished datal. Adults of these three species are commonly encountered in grain, and in and around grain storage facilities in Kansas (Reed et al. 1989). The laboratory tests reported here were designed to identify food materials, other than the food-bait mixture, that could be used as baits for detecting adults of the tlwee species in grain stores, ware­houses, on farms and in countr'y elevators in Kansas.

Materials and Methods

Insects. Sitophilus oryzae was cultured 011 whole wheat kernels, C. pusillus on rolled oats plus 5% brewer's yeast (w/w), and T. castaneum on whole wheat Oour plus 5% brewer's yeast diet. All species were reared in a room maintained at 27 ± 1°C and 65 ± 5% RH with 14:10 light:dark cycle.

Foods. Kernels of whole corn, wheat, and sorghum of 14.5% moisture con­tent (m.c.) were cracked in a Stein laboratory mill (Fred Stein Laboratories, Inc., Atchison, Kansas). Rolled oats (13.3% m.c.) were used without crushing. Kibbled carob pods (Frontier Herbs} Norway, Iowa; 22.4% m.c.) were cut into small pieces with scissors. Cracked corn and carob pieces that passed through a 6.7-mm sieve but were retained on a 2.0-mm sieve, and cracked wheat and sorghum that passed through a 6.7-mm sieve but were retained on a l.6-mm sieve, were used in the tests. Corn, wheat, and sorghum were freshly cracked, and carobs were freshly cut before use. Whole grains, rolled oats, and kibbled carobs were stored in a cold chamber (7.8°C) in sealed containers until they were needed.

Test arenas. Free-choice tests, using cracked grains, rolled oats, and carobs, were performed in circular wooden arenas (41.5-cm internal diam and 5-cm high). The bottom of each arena was lined with brown wrapping paper, and the edges of the paper were tightly sealed to the inner sides of the arena with mask­ing tape. The paper and tape were replaced after each test. The inner sides of the arenas (above the masking tape) were coated with polytetrafluoroethylene (Teflon) to prevent insects from crawling out.

General procedure for choice tests and data analysis. Five grams (g) of autoclaved aquarium gravel (control) or each food component was placed in sep­arate square plastic boxes (4.5 cm2 by 1.5 cm high). The number of boxes per arena was one (no-choice test), two (dual-choice test), or four (four-choice test). In each arena, the boxes containing gravel or food materials were placed at random in the north, south, west, or east edges (no-choice test); in the north and south edges (dual-choice test); or in the north, south, west, and east edges (four-choice test). A paper ramp (6 cm long by 4.7 cm wide, with a slightly tapered edge to fit into the box) was cut from plain index cards and placed at an incline leading to each box. These ramps, which pointed to the center, facilitat­ed movement of insects from a release point in the arena into and out of the boxes. For dual- and four-choice tests, a randomized block design was used, with the arenas serving as blocks (replicates).

120 J. Agric. Entomol. Vol. 9, No.2 (1992)

Newly emerged adults of the three species were separated from cultures, and 100 adults of each species were placed separately in 0.47-liter jars containing 100 g of the respective culture media. These jars were then transferred to the test room, which was maintained in total darkness at 27 ± lOC and 45 ± 5% RH. Insects were acclimated to the test conditions for 11 to 23 d. Each species was tested separately. In the center of each arena, 80 unsexed adults were released into a square plastic box lid (4.5 cm2 and 0.5 ern high), from which the insects could easily escape. Red lights were used only when working in the dark room. After releasing adults, each arena was closed with a lid (43 em diam) that had a 9-cm diam hole in the center. A wire-mesh screen covering the hole prevented insects from flying out, but permitted air diffusion. All tests were initiated between 1300 and 1700 h local time. After 24 h, dishes containing food were closed with lids, labeled, and frozen (-13'C) for 1-2 d to kill the insects. The number of adults in each dish was later counted.

Data from four-choice tests were subjected to two-way analysis of variance (ANOVA), to partition the variation among arenas (blocks) and foods/gravel (treatments) in the number of adults retained. Differences (P < 0.05) among foods/gravel in the number of adults retained were determined by Bonferroni t-tests (SAS Institute 1988). For dual-choice tests, a paired t-test was used to compare treatment differences (P < 0.05) (SAS Institute 1987). Data (z) for all analyses were transformed to logIQ(z) or 10glQ(z + 1) scale to stabilize variances across or between treatments.

Determining the suitability of arenas for choice tests. Because the arenas used were relatively small, it is conceivable that insects could be found in foods due to random movement. To assess such random movement, we presented an inert material (autoclaved aquarium gravel) to the insects. In the first test, one plastic box containing 5 g of gravel (similar in particle size to cracked corn) was placed at random in each arena. For each species, three such arenas were used. In the second test, four plastic boxes each containing 5 g of gravel were presented to insects in each arena. For each species, three arenas were used. In the third test, four plastic boxes each containing 5 g of freshly cracked corn, wheat, sorghum, or gravel were presented to insects in each arena. For each species, five arenas were used. The number of adults in boxes containing bll'avel or cracked grains and grav­el after 24 h was counted. Data from the second and third test were subjected to two-way ANOVA and Bonferroni i-tests, as explained above.

Four-choice test with cracked grains and rolled oats. Five grams of rolled oats was compared with similar amounts of cracked corn, wheat, and sorghum in each arena. For tests with S. oryzae adults, six arenas were used. For the remaining species, eight arenas were used.

Four~choice test with cracked grains and kibbled carobs. In each arena, fOUf boxes each containing 5 g of freshly cracked corn, wheat and sorghum, or carobs were presented to adults of each insect species. For each species, nine arenas were used.

Four-choice test with cracked grains and food-bait mixture. In each arena, 5 g of food bait mixture (cracked corn, cracked wheat, rolled oats, and carobs (1.554: 1.554: 1.554: 0.339 g, respectively; measured by a Mettler bal­ance) was compared with similar amounts of cracked corn, wheat and sorghum. Each species was tested separately using nine arenas.

121 SUBRAMANYAM el a1.: Detection ofStored-Producl Beetles

Dual-choice test with food-bait mixture with and without carobs. In each arena, one box containing 5 g of food-bait mixture with carobs was com­pared with a box containing 4.661 g (1.554 g each of cracked corn, cracked wheat, and rolled oats) of food-bait mixture without carobs. In the latter box, an equal number of styrofoam pieces (cut from a styrofoam cup) were added to sim­ulate the larger carob pieces. Each species was tested separately using nine are­nas, and the data were analyzed using a paired t-test.

Results

In all four-choice tests, the variation among arenas (blocks) in the number of adults responding to the food and nonfood (gravel) materials presented in the boxes was not significant (P = 0.07 - 0.98).

When one box containing gravel per arena was presented to each insect species for 24 h, a mean ± SEM of 13.0 ± 5.1, 5.3 ± 2.4, and 0.3 ± 0.3 adults of C. pusillus, 1'. castancwn, and S. oryzae, respectively, were retained in gravel. When four boxes each containing gravel were presented to the insects in each arena, ~ 8 adults of S. oryzae and C. pusiUus were retained in gravel in each of the four boxes (Table 1). However, the number of T. castaneum adults retained in gravel in each of the four boxes ranged from 1 to 21. For each species, the numbers of adults present among the four boxes of gravel were not significantly different (P" 0.30).

Table 1. Number of adult C. pusillus, T. castaneum, and S. oryzae retained in autoclaved aquarium gravel in a four-choice test/'

Number of adults per box per arenab,c (Mean ± SEM)

Box C. pusillus T. castaneum S. oryzae

A 8.0 ± 2.6 1.3± 0.9 1.7±1.7

B 7.7 ± 3.0 20.7 ± 12.5 5.3 ± 1.8

c 8.0 ± 3.1 4.3 ± 0.9 1.0 ± 1.0

D 6.0 ± 1.5 17.0 ± 9.5 1.3 ± 0.9

P-value 0.980 0.395 0.300

(/ For each speci~s, n =3 arenas. b For each spccics, differences among t.he four boxes in the numbcl' of adults retained ill gravel werc

not significant. (P:> 0.05, two-way ANGVAl. I: Raw dat~l for C. pusillus were transformcd to a log (z) scale lor analysis. Raw data for T crJsfallCUfll

and S. uryZ{lC were transformcd to a log (1, + 1) scale 1'01' analysis.

122 J. Agric. Entomol. Vol. 9, No.2 (1992)

In the presence of freshly cracked corn, wheat, and sorghum, fewer adults of all three species (mean = 0.8 to 7.0 adults per box) were retained in gravel (Table 2). The numbers of C. pusillu8 or S. oryzac ,"etained in the three grains were not significantly different (P > 0.05). Interestingly, there were no signifi· cant differences (P = 0.11) in the numbers of T. castaneum retained in the cracked grains and gravel.

Table 2. Number of adult C. pusillus, 1'. castaneUln, and S. oryzae retained in cracked corn, wheat and sorghum, and auto­claved aquarium gravel in a four-choice test/1

Number of adults per box per arenab

(Mean ± SEM)

Treatment C. pusillusc T. castancumU S.oryzaeC

Cracked corn 25.0 ± 4.5 a 14.2 ± 2.2 27.8 ± 2.0 a

Cracked wheat 16.4 ± 1.0 a 13.4 ± 2.5 24.8 ± 1.5 a

Cracked sorghum 23.2 ± 4.5 a 13.0 ± 3.4 19.2 ± 2.2 a

Gravel 2.6± 1.7 b 7.0 ± 5.5 0.8 ± 0.4 b

P-value <0.001 0.113 <0.001

a For each species, n =5 arenas. b Raw dOJtll were transformed to a log (z + 1) scnle for analysis. C Means in a column followed lJy same lelter arc not significantly different (P > 0.05, Bonfcrroni

i-tests). d Differences mllong cmckcu groins and grllvel in the number of adults retained were not significant

(P > 0.05, two-way ANQVA),

There were no differences (P > 0.25) in the numbers of C. pusillus or T. castaneum retained in cracked grains and rolled oats (Table 3). However, signif­icantly more (about twofold) S. oryzae adults were observed in cracked corn and wheat than in cracked sorghum or rolled oats.

Significantly fewer « 5; P < 0.05) adults of all three species were retained in carobs than in cracked corn, wheat,and sorghum (mean numbers retained ranged li'om 16-23 adults) (Table 4). The numbers ofC. pusillus or T. castaneurn found in cracked corn, wheat and sorghum were similar. However, significantly more (P < 0.05) S. OfJ!zae adults were found in cracked corn and wheat than in cracked sorghum.

The numbers of C. pusillus or T. castaneum adults retained in cracked grains and food-bait mixture were not sib'Tlificantly different (P > 0.10) (Table 5). The num­bers of S. oryzae retained in cracked corn, cracked wheat, and food~bait mixture were similar, but the number retained in cracked sorghum was significantly lower.

123 SUBRAMANYAM et al.: Detection of Stored-Product Beetles

Table 3. Number of adult C. pusillus, T. caslaneum, and S. oryzae retained in cracked grains and rolled oats in a four-choice test.a

Number of adults per box per arenab (Mean ± SEM)

Treatment C. pusillusc T. castaneumC S.oryzaed

Cracked corn 15.1 ± 3.7 20.3 ± 4.2 23.2 ± 1.9 a

Cracked wheat 11.0± 1.5 13.6 ± 2.9 25.5 ± 1.5 a

Cracked sorghum 15.6 ± 3.7 24.5 ± 4.3 11.7 ± 1.8 b

Rolled oats 16.4 ± 2.5 11.6 ± 2.4 9.3 ± 1.3 b

0.569 0.254P-value <0.001

a For C. pusillus and T. castallcum. n = 8 arenas; for S. Of)'zae. n = 6 arenas. b Rnw dat..'J. were lransfonncd to a log (z) scale for analysis. C Differences among cracked grains and rolled oats in the number of adults retained were not sig­

nificant (P > 0.05, two-way ANOVAJ. d Means followed by same letter arc not significantly different (P > 0.05, Bonferroni t-lcsl.s).

Table 4. Number of adult C. pusillus, T. castaneum, and S. oryzae retained in cracked grains and kibbled carobs in a four­choice test.a

Number of adults per box per arenab,c (Mean ± SEM)

Treatment C. pusillus

Cracked corn

Cracked wheat

Cracked sorghum

Kibbled carobs

15.9 ± 2.5 a

18.2 ± 2.5 a

19.6 ± 2.7 a

3.2 ± 1.2 b

T. castaneum S.oryzae

16.0 ± 4.7 a 23.2 ± 2.0 ab

17.8 ± 3.0 a 27.3 ± 1.3 a

14.7 ± 2.0 a 16.1 ± 1.8 b

4.7±0.7b 4.4 ± 0.7 c

(I For each species, n = 9 arenas. b Raw data were transformed to 11 log (z) scale for analysis. C Means in a column followed by slime letLer are not significantly different (P > 0.05, Bonferruni t-\..cslsl.

124 J. Agric. Entomol. Vol. 9, No.2 (1992)

Table 5. Number of adult C. pusillas, T. castaneum, and S. oryzae retained in cracked grains and food-bai.t mixture in a four­choice test/I

Number of adults per box per al'enab

(Mean ± SEM)

Treatment C. pusillusc T. castaneumC S.oryzaed

Cracked corn 13.2 ± 1.8 11.7±0.7 21.9 ± 0.6 a

Cracked wheat 13.9 ± 1.9 10.6 ± 1.0 19.8 ± 1.7 a

Cracked sorghum 22.0 ± 3.5 12.9 ± 1.4 10.8± 0.9 b

Food-bait mixture 18.8± 3.0 10.9 ± 0.6 22.2 ± 1.4 a

0.144 0.475P-value <0.001

fl For each species. n ,. 9 arenas. b R.-Iw data were transfonncd to a log (z) scale for analysis. C Differences among cracked grains and food-bait. mixture in the number of adults retained were

not significant. CP > 0.05, two-way ANOVA). d Means followed by same letter arc noL significantly different (P > 0.05, Bonfcrroni t-tests).

The numbers of C. pusillus or T. castaneum retained in the food-bait mixture with and without carobs were similar (P > 0.10) (Table 6). However, significantly more (1.4 times) S. oryzae adults were retained in the food-bait mixture with carobs than in the mixture without carobs.

Discussion

[n this study, the behavior of adults responding to the foods or gravel presented in the boxes was not analyzed. Only the number of adults still remaining in foods/gravel at 24 h was recorded. Therefore, these adults may represent insects that were initially attracted to the food volatiles, arrested and retained after con­tact with the foael/gravel, or insects that found spaces between the food/gravel suitable for concealment. In addition to the above, the role of aggregation pheromones in attracting additional adults to the food source and retaining these adults on the food source cannot be excluded. Males of each of these species produce aggregation pheromones that are attractive to both sexes (Burkholder and Ma 1985, Millar et aJ. 1985). For example, eightfold more S. oryzae adults were attracted when cracked corn and the aggregation pheromone of S. oryzae were presented together compared with cracked corn alone (Trematerra and Girgenti 1989). Similar synergism between cracked wheat and the aggregation pheromone was reported for the maize weevil, Silophilus zeamais Motschulsky. (Walgenbach et aJ. 1987). The maximum production of this male-produced aggre­gation pheromone in Silophilus spp. occurs in the presence of foods (Walgenbach et aJ. 1983), resulting in the aggregation of adults for the purpose of exploiting the food source and for mating.

125 SUBRAl\'lANYAM at al.: Detection ofSlo,'cd·Product Beetles

Table 6. Number of adult C. pusillus, T. castaneum, and S. oryzae retained in food-bait mixture with and without kibbled carobs in a dual-choice test."

Number of adults per box per arenab,c (Mean ± SEM)

Food-bait mixture: C. pusillusc 1'. castaneumc S. OI)'ZOe"

with carobs 35.9 ± 3.4 28.1 ± 5.3 36.2 ± 3.2

without carobs 26.4 ± 2.3 15.1 ± 1.9 26.8 ± 2.4

DilT. d (Meand ± SEMd) 0.13 ± 0.07 0.23 ± 0.13 0.13 ± 0.03

P-value [d = 01 0.118 ns 0.109 ns <0,01**

a For each species. n = 9 arenas. b "'DilTerence bet.....een food-bait mixture ..... ith and .....ithout carobs in the number of adults ret..'lined

was significant (P < 0.05. paired I-Lest); ns. not significant. C R.'lW data .....ere transfonncd to a log (x) scale for analysis.

Insignificant block variation in each of the four-choice tests for each species indicated that the mean retention of adults in the test materials was consistent from arena to arena. The arenas, though small, were useful for quantifying the relative retentive ability of the food baits, because very few adults of the three species were retained in gravel when it was presented alone or in combination with cracked grains (Table 2). This enabled better gauging of the relative reten­tive abilities of the foods tested. However, the degree of response to gravel var­ied with the species. Adults of S. oryzae were least responsive to gravel, fol­lowed by C. pusillus and 1'. castaneum. For example, in a test with four boxes containing gravel, 17 and 21 adults of T. cas(.aneum were retained in boxes D and B, respectively (Table 1). Tribolium caslaneum adults and larvae normally conceal themselves under any suitable object (Good 1936). and the interstitial spaces between gravel pieces may have provided adequate harborage for adult concealment.

In two separate tests (Tables 2 and 3), the numbers of C. pusillus retained in the three cracked grains, and in cracked grains and rolled oats were similar. Therefore, any of the cracked grains or rolled oats could be used as bait for detecting C. pusillus. In the same tests, more S. oryzae adults were retained in cracked corn and wheat compared with cracked sorghum or rolled oats. Cracked corn and wheat, therefore, could be used as bait for detecting S. oryzae. 1'riboli­um castaneum did not show a marked preference for any of the cracked grains and rolled oats (Table 3). Although differences in numbers of T. castaneum retained in cracked grains and gravel were not significantly different Cfable 2), twice as many adults were present in cracked grains compared with gravel. As stated earlier, spaces between gravel pieces may have resulted in T. caslaneum seeking refuge in gravel in spite of any volatile (olfactory) or nonvolatile (aggre­gant) stimuli, This refuge·seeking behavior of T. castaneum has been taken into

126 J. Agric. Entomol. Vol. 9, No, 2 (1992)

consideration in commercial food~baited trap designs (see Barak and Burkholder 1984).

Carobs are attractive to adults of T. castaneum, sawtoothed grain beetle, Oryzaephilus surinamensis (L.), and granary weevil, Sitophilu8 granarius (L.) (Pinniger et a!. 1984). Pinniger et aI. (1984) and O'Donnell et a!. (1983) have iden­tified the attractive components of carobs. In addition to being attractive, carobs also support infestation of a variety of stored-product insects (Ashman 1967). In our study, carobs retained about thl'ee- to sixfold fewer adults of the three species than cracked grains (Table 4). Our results with T. castaneum are contrary to those reported by Pinniger et a1. (1984), We cannot explain this low level of retention in carobs. Perhaps, the concentration of carob volatiles from 5 g of carobs had an adverse (inhibitory) effect on the response of these three species.

The numbers of C. pusillus or T. castaneutn retained in cracked grains and food-bait mixture were similar. This indicated that the cracked grains could be used instead of the food-bait mixture for detecting these two species. The num­bers of S. oryzae adults retained in cracked corn, cracked wheat, and food~bait

mixture were similar. Therefore, for detecting S. or)lzae, cracked com or wheat could be substituted for the food-bait mixture.

The presence of carobs in the food-bait mixture did not greatly enhance the retention of any of the three species. Although significantly more (P < 0.01) S. oryzae adults were retained in the food-bait mixture with carobs than without carobs, the lA-fold difference observed is too small to justify the inclu­sion of carobs in the food-bait mixture.

In summary, cracked corn, wheat and sorghum, or rolled oats could be used as bait for detecting adults of C. pusillus and T. castaneum, whereas cracked corn or cracked wheat could be used as bait for detecting S. oryzae adults. Because extrapolation of laboratory data to field situations is risky, traps or wire~mesh envelopes containing these food baits must be evaluated in the field for their effectiveness in detecting adults of these three species, and other stored-product insects.

Acknowledgment

Research reported here was performed in the Department of Entomology, Kansas State University, Manhattan, K<:"tnsas 66506, during 1988-89, and was funded by a USDA grant (CSRS 88-34165-3315). We thank Nahid Tavokkal, Saeeda Nikayum, and Milton McCabe for technical assistance. Thanks to Barry Dover, John Pedersen, David Hagstrum, and two anonymous reviewers for critical comments on the manuscript. This paper is Kansas Agricultural Experiment Station Contribution 91~359·J.

References Cited

Ashman, F. 1967. The control of infestation in carobs (Ceralonia siliqua L.l with special reference to Cyprus. Eur. Mediten. Plant Prot. Organ. Pub!. SCI'. A 46E: 117·120.

Barak, A. V. 1989. Development of a new trap to detect and monitor khapra beetle (Coleoptera: Dermestidae). J. Econ. Entomol. 82: 10170-1477.

Barak, A. V., and W. E. Burkholder. 1984. A versatile and effective trap for detecting and monitoring stored-product Coleoplera. Ab'tJ'ic. Ecosys. & Environ. 12: 207-218.

Barrer, P. M. 1983. A field demonstration of odour-based host-food finding behaviour in several species of stored grain insects. J. Stored Prod. Res. 19: 105-110.

127 SUBRAMANYAM ct al.: Detection of Stored-Product Beetles

Burkholder, W. E., and M. Ma. 1985. Pheromones for monitoring and control of stored­product insects. Annu. Rev. Entomol. 30: 257·272.

Good, N. E. 1936. The flour beetles of the genus Tribolium. United States Department of Abrriculture Technical Bulletin 498, Washington, D.C., 57 pp.

Hodges, R. J., H. Halid, D. P. Rees, J.l'tIeik, aod J. Sarjooo. 1985. Insect traps as an aid to pest management in milled rice stores. J. Stored Prod. Res. 21: 215·229.

McFarlane, J. A. and C. Warui. 1973. A simple technique for stored product infesta­tion surveys. Trop. Stored P)·od. Inf. 24: 17·24.

Millar, J. G., H. D. Pierce, Jr., A. M. Pierce, A. C. Dehlschlager, J. H. Borden, and A. V. Barak. 1985. Aggregation pheromones of the Out grain beetIe, Cryplolcslcs pusil· ius (Coleoptera: Cucujidae). J. Chern. Ecol. 11: 1053·1070.

Nara, J. M., R. C. Lindsay, and W. E. Burkholder. 1981. Analysis of volatile com­pounds in wheat germ oil responsible for an aggregation response in Trogoderma glabrum larvae. J. Agric. Ii'ood Chern. 29: 68-72.

O'Donnell, M. J., J. Chambers, and S. M. McFarland. 1983. Attractancy to Oryzaephillls Sllri"amew,l1; (L.), saw-toothed grain beetle, of extracts of carobs, some triglyccrides, and related compounds. J. Chern. &01. 9: 357-374.

Ohsawa, K., K. Oshima, I. Yamamoto, and R. Ynmamoto. 1970. Attrachlllt for the rice weevil, Silophilus zeamais rVlotschulsky (Coleoptera: Rhynchophoridae), from rice grains. Ill. A new type of olfactometer for rice wecvils. App!. Entomol. Zool. 5: 121·125.

Pierce, AM., J. H. Bordcn, and A C. Oehlschlnger. 1981. Olfactory response to bee­tle-produced volatiles and host-food attractants by Or)'zaephilu.s su-rillomcllsis and O. mercator. Can. J. Zoo\. 59: 1980-1990.

Pinniger, D. B. 1975. A bait trap technique for assessment of stored product beetle popu­lations. Trop. Stored Prod. Inf. 19: 9-11.

Pinniger, D. 8., M. R. Stubbs, and J. Chambers. 1984. The evaluation of some food attractants for the detection of Oryzaephilus surinomcllsis (L.), and other storage pests, pp. 640-650. In Proceedings, Third lnternationnl Working Conference on Stored­Product Entomolob'Y, 23~28 October 1983, Kansas State University, Manhattan, 726 pp.

Reed, C., V. F. Wright, J. R. Pedersen, and K. Anderson. 1989. Effects of insect infes­tation of farm-stored wheat on its sale price at country and terminal elevators. J. Eeon. Entomo!. 82: 1254-1261.

SAS Institute. 198B. SAS/STAT user's guide. Release 6.03 cd. SAS Institute, Cary, North Carolina, 1028 pp.

Strong, R. G. 1970. Distribution and relative abundtlilce of stored products insects in California. A method for obtaining sample populations. J. Eeon. Entomol. 63: 591- 596.

Trcmaterra, P., and P. Girgenti. 1989. Innuence of pheromone and food attractants on trapping of Sitophilus oryzac (LJ (Col., Curculionidac): a new trap. J. Appl. Entomo!. 108: 12-20_

Walgcnbach, C. A, J. K. Phillips, D. L. Faustini, and W. E. Burkholder. 1983. Male-produced aggregation pheromone of the maize weevil, Sitophilll.s zeamais. and interspecific attraction beLween three Sitophilils species. J. Chern. Eco!. 9: 831·841.

Walgenbach, C. A., W. E. Burkholder, M. J. Curtis, and Z. A Khan. 1987. Labora­tory trapping studies with Silophilus zeamais (Coleoptera: Curculionidae). J. Econ. EnlomoL 80: 763-767.