Spotted Cucumber Beetle Research Articles

Development of an Insectary Plant Mixture for New Mexico and its Effect on Pests and Beneficial Insects Associated with Pumpkins

Abstract An insectary mixture of flowering annuals suitable for use in the high desert irrigated agriculture of New Mexico was developed over 3 years using pumpkins, Cucurbita moschata L., as a model cropping system. Plant establishment, survival, and flowering phenology were assessed in both clay and sandy soils by using weekly quadrat samples. Abundance of beneficial insects and spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber, were monitored with yellow sticky cards (Trece Inc., Adair, OK). Abundance of squash bug, Anasa tristis (DeGeer), was monitored weekly by sampling eggs and nymphs. Establishment of the flowering mixture was significantly better in clay than sandy soils in each of the 3 years. Of the fifteen plant species tested, California bluebell (Phacelia campanularia A. Gray), buckwheat (Fagopyrum esculentum Moench), dill (Anethum graveolens L.), Plains coreopsis (Coreopsis tinctoria Nuttall), garden cosmos (Cosmos bipinnatus Cavanilles), and sweet alyssum (Lobularia maritim...

Population dynamics of arthropods in a sunn-hemp zucchini interplanting system

Zucchini, Cucurbita pepo L., is often colonized by economically important insect pests such as the striped (Acalymma vittatum Fab.) and spotted (Diabrotica undecimpunctata howardi Barber) cucumber beetles. To evaluate the impact of an interplanted cover crop on arthropods associated with zucchini, field experiments were conducted in which sunn hemp (Crotalaria juncea L.) was interplanted with zucchini as a living mulch and compared with zucchini monoculture (bare-ground) during 2009, 2010 and 2011 growing seasons. The experiment consisted also of two types of fertilizer usage including the application of synthetic or organic fertilizer in the form of chicken manure. Foliar counts of arthropods conducted on zucchini plants showed significantly lower numbers of the striped cucumber beetle in sunn hemp interplanted plots compared to bare-ground treatment plots. Also, fewer spotted cucumber beetles were found on zucchini plants in sunn hemp plots. Aphid abundances were variable during the study and significantly lower in sunn hemp treatment plots at one study site in 2009. Among predators, spiders were significantly more abundant in sunn hemp treatment plots during 2009. Fertilizer type did not have a significant effect on arthropod numbers on zucchini plants. Potential causes of arthropod population differences among the two treatments are discussed.

Field and Vegetable Crops as Hosts of Larval Western Spotted Cucumber Beetle (Coleoptera: Chrysomelidae)

The western spotted cucumber beetle, Diabrotica undecimpunctata undecimpunctata Mannerheim, is an important pest of melons (Cucurmis melo L.) in northern California. Recent observations indicate that adults are using alfalfa (Medicago sativa L.) as a feeding host and larvae may be developing on the roots. Greenhouse studies were conducted during the winters of 2009 and 2010 in which larval development was compared on the roots of six field and vegetable crops commonly grown in the southern Sacramento Valley. The growth parameters used to evaluate the hosts were larval and pupal head capsule width, body width, and body length as well as total survival percentage and survival percentage to the third instar. According to larval growth and survivorship in 2009, maize (Zea mays L.) was the best host, followed by alfalfa and tomato (Solanum lycopersicum L.) that were roughly equivalent to one another. Melon was a slightly weaker host than alfalfa and tomato; sunflower (Helianthus annuus L.) was a completely incompatible host and thus dropped from the 2010 study. In 2010, melon was the weakest host for larval development. Maize was the superior host again followed closely by alfalfa that performed slightly better than tomato and lima bean (Phaseolus lunatus L.). Data suggest that larval western spotted cucumber beetles may primarily develop outside of melon fields and the adults emigrate to melons.

Female spotted cucumber beetles use own cuticular hydrocarbon signature to choose immunocompatible mates

Using spotted cucumber beetles and their epicuticular hydrocarbon signatures, we examined two hypotheses about how females may use signals that describe a potential mate’s immune system to identify high-quality males. Females may find males to be acceptable mates when (1) a male’s immune system complements or matches the immune system of the receptive female (immunocompatibility), or (2) a male successfully signals that it has a strong immune system (immunocompetence). The first experiment used gas chromatography to compare the epicuticular hydrocarbon signature of a female beetle with that of a male she rejected and a male she accepted as a mate. We also compared the hydrocarbon signatures of a male and two fertilized females, one that had voluntarily accepted his spermatophore and one that was forced to accept the spermatophore. In both experiments the immune response to an implant inserted in the insect’s abdomen was compared in males and their offspring. The hydrocarbon signature of males accepted as mates in the first experiment differed more from that of their female partners than did the hydrocarbon signature of rejected males. There was no significant difference in the immune response of accepted and rejected males. Offspring from forced matings had significantly lower immune responses than offspring from voluntary matings. This study suggests that females use immunocompatibility rather than immunocompetence as a trait to identify quality mates, which fosters stronger immune systems in offspring. Female choice of mates in this species may be self-referenced using the cuticular hydrocarbon signature of the female as a standard.

Capsid protein of cowpea chlorotic mottle virus is a determinant for vector transmission by a beetle

Cowpea chlorotic mottle virus (CCMV) is a bromovirus transmitted by species of chrysomelid beetles, including the spotted cucumber beetle, Diabrotica undecimpunctata howardii Barber. An experimental system was set up to identify the viral determinant(s) of the beetle transmission of CCMV. Nicotiana clevelandii was selected as an experimental plant host because it supports the replication and accumulation of both CCMV and a second member of the family Bromoviridae, cucumber mosaic virus (CMV). Using a reverse genetic system for CMV, a cDNA copy of the CCMV capsid protein (CP) gene was substituted for that of the CMV CP gene. The resulting 'CMV-hybrid' consisted of wild-type CMV RNA1, RNA2, and a chimeric CMV RNA3 expressing the CCMV structural protein. The CMV-hybrid replicated and formed virions in N. clevelandii; in electron micrographs the hybrid virus was indistinguishable from CCMV. In beetle feeding assays, both CCMV and the CMV-hybrid were transmitted by D. undecimpunctata, while beetle transmission of CMV was not observed. Conversely, only CMV was observed to be transmitted by the aphid Myzus persicae. Surprisingly, the CMV-hybrid was transmitted more efficiently than the parental CCMV, and a virus-induced alteration in beetle feeding behaviour is proposed to account for the difference. These results indicate that the CCMV CP is a viral determinant for beetle vector transmission.

Aggregation Behavior of Western Spotted Cucumber Beetle (Coleoptera: Chrysomelidae) in Vegetable Cropping Systems

Aggregation behavior of adult western spotted cucumber beetles (Diabrotica undecimpunctata undecimpunctata Mannerheim) (Coleoptera: Chrysomelidae) was examined in six snap bean (Phaseolus vulgaris) fields adjacent to corn fields in western Oregon in 2004-2006. In the 2004 and 2005 studies, sweep net sampling was used to estimate beetle numbers along transect lines running perpendicular to the edges of the bean fields next to sweet corn fields. Beetles were collected from the fields and dissected to determine sex and egg development. Beetles were highly aggregated along the edge of the snap bean field next to the sweet corn, with the highest number of beetles occurring within the first meter next to the edge. Beetles in the aggregation areas were mostly females (average female to male ratio of 8.4 to 1), whereas beetles in the field section away from the edges were mostly male (female to male ratio of 0.6 to 1). Of the females collected in the aggregation areas, an average of 53% contained developing or fully developed eggs. In the 2006 study, beetle densities in the field edges were compared with densities within the fields in 40 bean fields with adjacent corn fields. Linear regression analysis showed that, across fields, nearly two times as many beetles were found in the field borders as in the rest of the field. These data suggest modifying traditional field scouting protocol to include field margins when a bean field is adjacent to or near a sweet corn field. A pest management strategy of only spraying the edges of bean fields containing beetle aggregations shows potential for significant pesticide reduction, as well as reducing risk of economic loss from crops harvested from the highly aggregated areas.

‘Marketmore 97’: A Monoecious Slicing Cucumber Inbred with Multiple Disease and Insect Resistances

‘Marketmore 97’ is the most recent addition to a series of disease-resistant slicing cucumbers developed in the Cornell University Department of Plant Breeding. The fruit have green skin with white spines and an average length and diameter of 18.8 cm and 4.8 cm, respectively. Broad resistance to a number of destructive diseases and insects makes this cultivar well-suited to low-input agricultural systems at the scale of the home gardener or the commercial grower. In addition to the cucumber mosaic virus (CMV), cucumber scab (Cladosporium cucumerinum Ell. & Arth.), downy mildew (Pseudoperonospora cubensis Berk & Curtis), and powdery mildew (Sphaerotheca fuliginea Schl. ex Fr.) resistances of ‘Marketmore 76’, ‘Marketmore 97’ contains resistance to alternaria leaf spot [Alternaria alternata (Fr.) Keis.], Ulocladium leaf spot (Ulocladium cucurbitae Let. & Roum.), target leaf spot (Corynespora cassiicola Berk. & Curt.), watermelon mosaic virus, papaya ringspot virus, and zucchini yellow mosaic virus. Furthermore, the bitterfree character of this cultivar is responsible for nonpreference of the striped cucumber beetle (Acalymma vittatum Fab.) and spotted cucumber beetle (Diabrotica undecimpunctata howardi Barber). Finally, a near isogenic line of ‘Marketmore 97’ is available that is gynoecious. A replicated trial of ‘Marketmore 97’ conducted in New York in 2006 confirmed comparable yield and quality to other Marketmore cultivars.

Utility of Morphological and Molecular Techniques for Determination of Paternity in Two Subspecies of Diabrotica undecimpunctata (Coleoptera: Chrysomelidae)

An experiment was conducted to determine the paternity of F1 progeny using morphological and molecular methods in Diabrotica (Coleoptera: Chrysomelidae) subspecies: Diabrotica undecimpunctata howardi Barber, also known as spotted cucumber beetle, and D. undecimpunctata undecimpunctata Mannerheim, also known as western cucumber spotted beetle. Results from crosses that involved the females of D. u. howardi and the males of D. u. undecimpunctata had all F1 progeny with phenotypes as the male parent. Similarly, in all the crosses that involved the females of D. u. undecimpunctata and the males of the D. u. howardi, all the F1 progeny had phenotypes as the male parent. DNA from females and males were amplified using two primers to confirm the paternity of F1 progeny. The study on the inheritance of body color in these two subspecies appeared to be governed by one dominant gene (monogenic), and it is the male that determines the body color of progeny in both subspecies.

Resistance of Sweetpotato Genotypes to Adult Diabrotica Beetles

Production of sweetpotatoes, Ipomoea batatas (L.) Lam. (Convolvulaceae), is limited by several insect pests, including Diabrotica spp. (Coleoptera: Chrysomelidae), and new integrated pest management (IPM) techniques for this crop are needed. Host plant resistance is one attractive approach that fits well into IPM programs. A host plant resistance research program typically depends on reliable bioassay procedures to streamline evaluation of germplasm. Thus, a bioassay technique was developed for evaluating sweetpotato germplasm by using adults of the banded cucumber beetle, Diabrotica balteata LeConte, and spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber. A single beetle was placed on a piece of sweetpotato peel (periderm and cortex with stele removed) that was embedded periderm-side up in plaster in a petri dish. Feeding and longevity of insects on 30 sweetpotato genotypes were evaluated in two experiments by using this procedure. Adult longevity ranged from 7 to 11 d for starved individuals to 211 d for beetles fed a dry artificial diet. Longevity of banded cucumber beetles that fed on sweetpotato peels ranged from 12 d for the most-resistant genotype to 123 d for SC1149-19, a susceptible control cultivar. Longevity of spotted cucumber beetles was slightly shorter than longevity of banded cucumber beetles. For the most resistant sweetpotato genotypes, both Diabrotica species exhibited a significant delay in initiation of feeding, and more beetles died on these genotypes before they had fed. Both antibiosis and nonpreference (antixenosis) are important mechanisms of resistance in sweetpotato genotypes. This bioassay was consistent with field results, indicating that this technique could be useful for evaluating resistance to Diabrotica spp. in sweetpotato genotypes.

Resistance of Sweetpotato Genotypes to Adult <I>Diabrotica</I> Beetles

Production of sweetpotatoes, Ipomoea batatas (L.) Lam. (Convolvulaceae), is limited by several insect pests, including Diabrotica spp. (Coleoptera: Chrysomelidae), and new integrated pest management (IPM) techniques for this crop are needed. Host plant resistance is one attractive approach that fits well into IPM programs. A host plant resistance research program typically depends on reliable bioassay procedures to streamline evaluation of germplasm. Thus, a bioassay technique was developed for evaluating sweetpotato germplasm by using adults of the banded cucumber beetle, Diabrotica balteata LeConte, and spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber. A single beetle was placed on a piece of sweetpotato peel (periderm and cortex with stele removed) that was embedded periderm-side up in plaster in a petri dish. Feeding and longevity of insects on 30 sweetpotato genotypes were evaluated in two experiments by using this procedure. Adult longevity ranged from 7 to 11 d for starved individuals to 211 d for beetles fed a dry artificial diet. Longevity of banded cucumber beetles that fed on sweetpotato peels ranged from 12 d for the most-resistant genotype to 123 d for SC1149-19, a susceptible control cultivar. Longevity of spotted cucumber beetles was slightly shorter than longevity of banded cucumber beetles. For the most resistant sweetpotato genotypes, both Diabrotica species exhibited a significant delay in initiation of feeding, and more beetles died on these genotypes before they had fed. Both antibiosis and nonpreference (antixenosis) are important mechanisms of resistance in sweetpotato genotypes. This bioassay was consistent with field results, indicating that this technique could be useful for evaluating resistance to Diabrotica spp. in sweetpotato genotypes.

Female Choice by Scent Recognition in the Spotted Cucumber Beetle

AbstractIn species that demonstrate female choice, geographically distinct populations can vary in their signal‐response behaviors as a result of environmental differences or genetic drift. Observing whether or not females discriminate against males from allopatric populations can establish such signal deviations. Here we compare mating success within and between populations of the spotted cucumber beetle (Diabrotica undecimpunctata howardi) collected from Delaware, Tennessee, Missouri, and New Mexico, USA. A no‐choice cross‐mating experiment was employed to measure female preference for sympatric and allopatric males. While only two of the populations (Tennessee and Missouri) demonstrated statistically significant female preference for sympatric males, this trend was observed in all populations tested. Further, we show that (i) males from Tennessee, Missouri, and New Mexico differ in their scent, (ii) females may use population‐specific scents to discriminate among males, and (iii) females whose antennae have been surgically removed are unable to recognize acceptable mates. New Mexico males, which were never accepted by either Tennessee or Missouri females, became acceptable mates when crowded with Tennessee or Missouri males prior to copulation. We infer that male odor may be an important factor in determining cucumber beetle mating success.

Effect of Row Covers on Suppression of Bacterial Wilt of Muskmelon in Iowa

Spun polyester row covers, alone and in combination with insecticides, were evaluated for management of bacterial wilt of muskmelon at three locations in Iowa during 2003 and 2004. Following removal of row covers at bloom, more spotted cucumber beetles were counted in the plots with row covers than in the non-covered plots. Row covers delayed the onset of bacterial wilt symptoms and reduced bacterial wilt incidence. In both years, row covers increased both number and yield of marketable melons. There were no significant differences in beetle counts or melon yield among insecticide treatments in 2003. In 2004, however, each of the insecticide treatments had more marketable melons than the non-treated control. Row covers may enable cucurbit growers to reduce reliance on insecticides for managing bacterial wilt.Accepted for publication 31 July 2006. Published 20 October 2006.

Suppression of tomato hornworm ( Manduca quinquemaculata) and cucumber beetles ( Acalymma vittatum and Diabotrica undecimpunctata) populations and damage by vermicomposts

Summary The effects of food waste vermicompost on populations of adult striped cucumber beetles ( Acalymma vittatum) and spotted cucumber beetles ( Diabotrica undecimpunctata ) on cucumbers and larval hornworms on tomatoes ( Manduca quinquemaculata) were evaluated in both greenhouse and field experiments as well as damage caused. In the field, cucumber and tomato plants were grown, with two different application rates (1.25 and 2.5 t ha −1 ) of food waste vermicompost or inorganic fertilizer, in a complete randomized block design field experiment. All treatments were balanced for NPK. Field cucumber beetle populations were suppressed significantly on cucumber plants treated with food waste vermicompost at both application rates, compared with those on plants treated only with inorganic fertilizer. In the greenhouse, cucumber and tomato plants were grown in a soil-less medium MetroMix 360 (MM360) substituted with 0%, 20% or 40% food waste vermicompost, and exposed to standardized pest attacks in nylon mesh cages. In the greenhouse, both the 20% and 40% vermicompost substitution rates decreased damage by cucumber beetles to cucumber foliage and hornworms to tomato foliage significantly.

Monitoring Cucumber Beetles in Sweetpotato and Cucurbits with Kairomone-Baited Traps

Seven kairomone formulations (Trécé, Inc., Salinas, CA) were evaluated for their effectiveness as attractants for luring three species of cucumber beetles into Pherocon CRW traps (Trécé, Inc.) in cucurbit and sweetpotato fields. The spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber; the banded cucumber beetle, Diabrotica balteata LeConte; and the striped cucumber beetle, Acalymma vittatum (F.), were captured in this study. TRE8276 (TIC mixture: 500 mg of 1,2,4-trimethoxybenzene, 500 mg of indole, and 500 mg of trans-cinnamaldeyde) and TRE8336 (500 mg of 1,2,4-trimethoxybenzene, 500 mg of trans-cinnamaldeyde, 500 mg of 4-methoxyphenethanol) were the most effective lures for spotted and striped cucumber beetles. None of the kairomone lures was very effective for attracting banded cucumber beetles. Three population peaks of spotted cucumber beetles were observed in cucurbit and sweetpotato fields at the U.S. Vegetable Laboratory (Charleston, SC). The efficacy of TRE8276 declined rapidly after 2 wk in the field. An improved design of the Pherocon CRW trap, with a yellow bottom and more-tapered top section, was more effective for capturing cucumber beetles than the original trap design made entirely of clear plastic. Banded cucumber beetles were not captured in sweetpotato fields at inland locations in North Carolina or South Carolina.

Induced Systemic Resistance and Promotion of Plant Growth by Bacillus spp.

ABSTRACT Elicitation of induced systemic resistance (ISR) by plant-associated bacteria was initially demonstrated using Pseudomonas spp. and other gram-negative bacteria. Several reviews have summarized various aspects of the large volume of literature on Pseudomonas spp. as elicitors of ISR. Fewer published accounts of ISR by Bacillus spp. are available, and we review this literature for the first time. Published results are summarized showing that specific strains of the species B. amyloliquefaciens, B. subtilis, B. pasteurii, B. cereus, B. pumilus, B. mycoides, and B. sphaericus elicit significant reductions in the incidence or severity of various diseases on a diversity of hosts. Elicitation of ISR by these strains has been demonstrated in greenhouse or field trials on tomato, bell pepper, muskmelon, watermelon, sugar beet, tobacco, Arabidopsis sp., cucumber, loblolly pine, and two tropical crops (long cayenne pepper and green kuang futsoi). Protection resulting from ISR elicited by Bacillus spp. has been reported against leaf-spotting fungal and bacterial pathogens, systemic viruses, a crown-rotting fungal pathogen, root-knot nematodes, and a stem-blight fungal pathogen as well as damping-off, blue mold, and late blight diseases. Reductions in populations of three insect vectors have also been noted in the field: striped and spotted cucumber beetles that transmit cucurbit wilt disease and the silver leaf whitefly that transmits Tomato mottle virus. In most cases, Bacillus spp. that elicit ISR also elicit plant growth promotion. Studies on mechanisms indicate that elicitation of ISR by Bacillus spp. is associated with ultrastructural changes in plants during pathogen attack and with cytochemical alterations. Investigations into the signal transduction pathways of elicited plants suggest that Bacillus spp. activate some of the same pathways as Pseudomonas spp. and some additional pathways. For example, ISR elicited by several strains of Bacillus spp. is independent of salicylic acid but dependent on jasmonic acid, ethylene, and the regulatory gene NPR1-results that are in agreement with the model for ISR elicited by Pseudomonas spp. However, in other cases, ISR elicited by Bacillus spp. is dependent on salicylic acid and independent of jasmonic acid and NPR1. In addition, while ISR by Pseudomonas spp. does not lead to accumulation of the defense gene PR1 in plants, in some cases, ISR by Bacillus spp. does. Based on the strains and results summarized in this review, two products for commercial agriculture have been developed, one aimed mainly at plant growth promotion for transplanted vegetables and one, which has received registration from the U.S. Environmental Protection Agency, for disease protection on soybean.

Diabrotica virgifera

<i>Diabrotica virgifera</i>

Copulatory courtship signals male genetic quality in cucumber beetles.

In the spotted cucumber beetle, Diabrotica undecimpunctata howardi (Coleoptera: Chrysomelidae), males court females during copulation by stroking them with their antennae. Stroking occurs exclusively during the first stages of copulation, after a male has penetrated a female's vaginal duct but before he is allowed access to her bursa copulatrix. Females accept the spermatophore of fast-stroking males and reject those of slow-stroking males by relaxing or constricting muscles distorting the vaginal duct. Here, we measure the repeatability of stroking behaviour within males, examine the effect of losing one antenna on male attractiveness and test whether such female control results in direct phenotypic benefits for the discriminating female or indirect genetic benefits that appear in her offspring. We also use a half-sibling design to quantify the variance and heritability of stroking speed and endurance. Female beetles were paired with a male that was known to stroke either quickly or slowly. No difference was found in the resulting fecundity or egg-hatching rate of the females, or in the survivorship, development rate, size, age at first reproduction or fecundity of their offspring indicating that no direct benefits are gained by discriminating among males on the basis of stroking speed. There were, however, good-genes benefits for the mates of fast-stroking males. Offspring of fast-stroking fathers were also fast strokers and were more likely to be accepted as mates than offspring of slow-stroking fathers. There was substantial variance among sires in stroking speed and endurance and the heritability of each trait was high. The antennal stroking rate was highly repeatable in successive mating attempts and males with only one antenna were not accepted as mates. The repeatability within males, variability between males and heritability between generations of copulatory stroking combine to provide females with a reliable and honest signal of the genetic quality of courting males.

EVALUATION OF SOIL APPLIED INSECTICIDES FOR CONTROL OF CUCUMBER BEETLES ON SUMMER SQUASH, 2002

The objective of the study was to evaluate the effectiveness of soil insecticide for management of cucumber beetles on seedling squash. Plots were located on the University of Arkansas Vegetable Station, Kibler, AR. Soil type is Roxanna silt loam. Plots consisted of a single six foot wide bed 35 ft long. Experimental design was RCB with four replications. Black Beauty zucchini squash was planted with a single cone Hege planter on 29 Apr 2002. Seed was placed every 1 ft within each plot. Insecticide treatments applied at planting were applied within the planting furrow with a single TeeJet 8002E nozzle positioned just behind the seed tube and in front of the press wheel. The sprayer was propelled with CO2 and calibrated to deliver 2864 ml per 1,000 row ft at 25 psi (126 ml/15 s). Planter speed was 2 mph or 341 s/1,000 row ft. Additional insecticide treatments were applied when adult cucumber beetles reached the threshold of two per seedling (two unfolded true leaves). Treatments were applied as described for the planting applications with the exception of treatment location which follows. A 1.5-inch wide plow with open bottom was fitted with the single nozzle of the sprayer and run with a Kubota tractor (4th gear at the rate 1900 rpm) approximately 3 inches from one side of the drill line. Depth was approximately 4 inches. Sampling was initiated on 16 May when plants had two true leaves. Five sample areas each 18 inch x 18 inch, were randomly selected along the drill line of each plot. Plants and ground within each of the five areas were searched for dead (inability to walk) striped and spotted cucumber beetles. Also, within each sample area the two cotyledon bottoms of each of two plants were rated for cucumber beetle feeding. Ratings ranged from 0 (no damage) to 5 (completely damaged). Data were analyzed with ANOVA and LSD.

Male traits under cryptic female choice in the spotted cucumber beetle (Coleoptera: Chrysomelidae)

Males of the spotted cucumber beetle (Diabrotica undecimpunctata howardi) rhythmically stroke females with their antennae during copulation. Males that stroke quickly have a higher probability of being accepted as a mate. We determined (1) the mechanism by which females prevent unattractive males from passing spermatophores, (2) whether antennal stroking signals to females the likelihood of receiving a nuptial gift, and (3) if other male traits in addition to stroking are subjected to sexual selection from female preference. Dissections of pairs flash-frozen in copula during and after antennal stroking showed musculature that, when contracted, folded the vaginal duct leading to the female’s bursa copulatrix in a way that prevented complete penetration by the aedeagus. These muscles were always contracted while males were stroking and always relaxed after stroking had ceased. Males accepted as mates did not differ from males that failed to pass a spermatophore in either absolute or relative body weight, aedeagus length, or the amount of cucurbitacins (potential nuptial gifts) sequestered in their spermatophores. Although 99% of the beetles that came to cucurbitacin-rich Cucurbita fruits in the field were males, males that had sequestered cucurbitacins did not stroke females faster than males with no cucurbitacins, and fast-stroking males were not more likely to find and sequester cucurbitacins than were males that stroked more slowly. Males with a cucurbitacin slurry painted on their antennae had no mating advantage over controls. We conclude that females discriminate among males after copulation has begun on the basis of antennal stroking displays (or some trait correlated with stroking speed) that males perform to entice females to relax their bursal sphincter. Key words: copulatory courtship, cryptic female choice, Diabrotica undecimpunctata, sexual selection. [Behav Ecol 13:511–518 (2002)]

Stabilization of cucurbitacin E-glycoside, a feeding stimulant for diabroticite beetles, extracted from bitter Hawkesbury watermelon

Cucurbitacins are feeding stimulants for diabroticite beetles, including corn rootworms and cucumber beetles, which can be added to a bait containing an insecticide thereby reducing the levels of other insecticide treatments needed to control these pests. One of them, cucurbitacin E-glycoside, is water soluble and easily processed from mutant bitter Hawkesbury watermelons (BHW) that express elevated levels of cucurbitacin. Storage of BHW extract at room temperature resulted in a 92% reduction of cucurbitacin E-glycoside over two months, while refrigeration or freezing resulted in a 60% loss of the active ingredient during this time. The loss of the active ingredient was correlated with an increase in BHW extract pH from 5 to greater than 9. The increase in pH of the BHW extracts at room temperature appeared to be due to the growth of certain bacteria, especially Bacillusspp. In refrigerated extracts, the pH remained relatively constant, and bacterial growth was dominated by bacteria such as Lactobacilli. An alternative to refrigeration is concentration of BHW extract. One means of concentration is spray drying, but the high sugar content of the BHW extract (20mg/ml glucose, 40mg/ml fructose) makes this technique impractical. Fermentation of the BHW extract by the yeast, Saccharomyces boulardii, eliminated the sugars and did not raise the pH nor alter the cucurbitacin E-glycoside content of the extract. Elimination of the sugars by fermentation produced an extract that could be successfully spray dried. BHW extract fermented by S. boulardii produced a higher level of feeding stimulation for spotted cucumber beetles in laboratory choice tests. When applied to cucumbers, there was no difference in control of spotted and striped cucumber beetles between baits of fresh or fermented juices combined with the same insecticide.