William W. Cantelo

Corn silk volatiles attract many pest species of moths

Abstract The volatile components (ppm of total solids) emitted by corn silk were found to be l‐butanol (1), 1‐pentanol (7), 1‐hexanol (1), (E)‐4‐hexen‐1‐ol (4), 3‐methyl‐1‐butanol (1), acetaldehyde (5), hexanal (4), 2‐furancarboxaldehyde (furfural) (2), and phenylacetaldehyde (12). Phenylacetaldehyde was found to attract the corn earworm, European corn borer, soybean looper, tarnished plant bug, Cisseps fulvicollis, and forage looper. Combining phenylacetaldehyde with butanol or acetaldehyde increased attractiveness to some species; other combinations reduced attractiveness.

The effect of light intensity on Colorado potato beetle resistance and foliar glycoalkaloid concentration of fourSolanum chacoense clones

Controlled environment experiments were used to determine the effect of light intensity on levels of glycoalkaloids and resistance to the Colorado potato beetle (CPB),Leptinotarsa decemlineata Say, inSolanum chacoense Bitter clones that synthesized acetylated glycoalkaloids, the leptines. Plants were grown under two light intensities, 50 or 250 ώmol m-2S-1, and bioassayed for CPB resistance by placing neonate larvae on excised foliage. Larval development stage and mortality were recorded after four days. The leptine-synthesizing clones responded to the increase in light intensity with a 2–4 fold increase in level of foliar leptines. Larval development rate on foliage from plants grown under high light intensity was reduced and larval mortality increased. Results showed a significant (p>0.05) effect of light on glycoalkaloid synthesis and CPB resistance.CompendioSe realizaron experimentos de ambiente controlado para determinar el efecto de la intensidad de la luz sobre los niveles de glicoalcaloides y la resistencia al escarabajo de la papa de Colorado (EPC),Leptinotarsa decemlineata Say, en clones deSolanum chacoense Bitter que sintetizan glicoalcaloides acetilados, las leptinas. Se mantuvo plantas bajo dos intensidades de luz, 50 o 250 ώmol m−2s−1, y se probaron para resistencia al EPC colocando larvas recién emergidas sobre follaje extirpado. Se registraron el estado de desarrollo de las larvas y su mortalidad después de cuatro días. Los clones sintetizadores de leptina respondieron al incremento en la intensidad luminosa con un aumento de 2 a 4 veces en el nivel de leptinas en las hojas. La tasa de desarrollo de las larvas sobre el follaje de plantas que crecieron bajo una alta intensidad luminosa fue reducida, pero la mortalidad de las larvas se incrementó. Los resultados muestran un efecto significativo (p>0,05) de la luz sobre la síntesis de glicoalcaloides y sobre la resistencia al EPC.

Bioassays of segregating plants. A strategy for studying chemical defenses

Solanum chacoense is a wild potato species resistant to the Colorado potato beetle,Leptinotarsa decemlineata. Most genotypes ofS. chacoense synthesize the glycoalkaloids solanine (sol) and chaconine (chac) and are hosts of the beetle. A few rare genotypes have a gene(s) for acetylation of carbon-23 of the steroid aglycone of sol and chac. Laboratory bioassays and replicated field tests of clones differing in the presence or absence of the acetyl moiety showed that acetylation of sol and chac markedly affects the response of both adults and larvae to the foliage. Adult feeding deterrency conferred by acetylated forms of sol and chac (leptines) in leaf-disk preference tests was consistent with the degree of antixenosis measured in the field. Development of larvae on foliage of clones with leptines was also inhibited. The studies support the validity of using laboratory bioassays of plants segregating for levels of a suspected defense compound to determine the role the compound has in defending the plant from attack by an insect predator in the field.

Mortality of potato leafhopper adults on synthetic diets containing seven glycoalkaloids synthesized in the foliage of variousSolanum species

The glycoalkaloids solanine, chaconine, leptine I, leptine II, solasonine, solamargine, and tomatine, synthesized in the foliage of variousSolanum species, were tested in synthetic diets for their effects on potato leafhopper adults,Empoasca fabae (Harris), at concentrations of 0.03%, 0.09%, and 0.27%. Percent mortality was recorded after a 72 hr feeding period.At the lowest concentration (0.03%), tomatine in the diet resulted in the highest adult mortality (95%) with mortalities ranging from 10% to 41% in the other glycoalkaloid diets. At the highest concentration (0.27%) mortalities ranged from 69% to 100% with no significant (P>.05) differences among the diets.Mortality varied the most among the glycoalkaloid diets at the 0.09% concentration. Chaconine, ubiquitously found with solanine inSolanum tuberosum L., caused significantly (P≤.05) higher mortality (59%) than did solanine (8%). Mortalities with solasonine and solamargine in the diets (55% and 54%, respectively) were not significantly (P>.05) different from the mortality with chaconine in the diet. Including leptines I and II in diets resulted in lower mortalities (28% and 30%, respectively). Mortality was significantly (P≤.05) the highest (97%) with tomatine in the diet.CompendioLos glicoalcaloides solanina, chaconina, leptina I, leptina II, solasonina, solamargina y tomatina, que son sintetizados en el follaje de varias especies deSolanum, fueron probados en dietas sintéticas para medir sus efectos en los saltahojas adultos de la papa,Empoasca fabae Harris, en concentraciones de 0.03%, 0.09% y 0.27%. El porcentaje de mortalidad fue registrado luego de un período de alimentación de 72 horas.La tomatina de la dieta a la concentración más baja (0.03%) produjo el porcentaje de mortalidad más alto de adultos (95%), mientras que la mortalidad producida por las dietas de otros glicoalcaloides varió entre 10% y 41%. A la concentración más alta (0.27%) el rango de mortalidad fluctuó entre 69% y 100%, sin diferencias significativas (P>05) entre las dietas.Hubo mayor variation en el porcentaje de mortalidad cuando se usaron dietas con glicoalcaloides en una concentración de 0.09%. La chaconina, que se encuentra siempre junto con la solanina enSolanum tuberosum L., causó una mortalidad (59%) significativamente mayor (P>.05) que la de la solanina (8%). La mortalidad ocasionada por las dietas con solasonina y solamargina (55% y 54%, respectivamente) no mostró diferencias significativas (P>.05) en comparación con la mortalidad ocasionada por la chaconina. La inclusion de las leptinas I y II en las dietas dio como resultado menores porcentajes de mortalidad (28% y 30%, respectivamente). Este porcentaje fue significativamente mayor (P<.05) en la dieta con tomatina.

Susceptibility of Prepupae of the Colorado Potato Beetle (Coleoptera: Chrysomelidae) to Entomopathogenic Nematodes (Rhabditida: Steinernematidae, Heterorhabditidae)

This research investigated the ability of five species or strains of parasitic nematodes to control the Colorado potato beetle, Leptinotarsa decemlineata (Say), when beetle prepupae were released on potting soil containing the nematodes. The nematodes tested were: Steinernema carpocapsae Weiser (All strain); S. carpocapsae (Mexican strain); S. feltiae (= bibionis) (Filipjev) (strain #27); S. feltiae (strain #980) and Heterorhabditis bacteriophora Poinar. Six dosage levels ranging from 10.3 to 329.2 nematodes/cm2, in addition to the water-only controls, were used in these laboratory tests. Each dosage-strain combination was replicated four times with 20 prepupae exposed to each individual treatment. The five strains demonstrated 100% kill at 164.6 nematodes/cm2. Except for the Mexican strain of S. carpocapsae, every strain produced over 98% mortality at 82.3 nematodes/cm2. Dosage response regression equations were calculated for each strain. Although field applications probably would require higher rates t...

Larval development rate and mortality of Colorado potato beetle on detached leaves of wildSolanum species

Significant differences were found in larval development rate and mortality of Colorado potato beetle,Leptinotarsa decemlineata (Say), among nine wild, tuber-bearingSolatium species by placing neonate larvae on detached leaves.S. pinnatisectum Hawkes, 5.polyadenium Greenm., andS. trifidum Corn restricted development the most, 5.berthaultii Hawkes was intermediate, andS. canasense Hawkes,S. demissum Lindl.,S. megistacrolobum Bitt.,S. spegazzinii Bitt., andS. tarijense Hawkes restricted development the least. All tested species restricted development more than did the cultivar Kennebec. The measure of larval development rate and mortality was weakly correlated with foliar defoliation in field tests based on species-accession means (r= + 0.6, P<.01), but moderately correlated based on overall species means (r=+0.86, P<.01).CompendioSe encontraron diferencias significativas en la tasa de desarrollo larval y la mortalidad del escarabajo de la papa de Colorado,Leptinotarsa decemlineata (Say), entre nueve especies tuberosas silvestres deSolarium, colocando larvas recientemente emergidas sobre hojas separadas.S. pinnatisectum Hawkes,S. polyadenium Greenm., yS. trifidum Corr. fueron las que mas restringieron el desarrollo,S, berthaultii Hawkes fue intermedia yS. canasense Hawkes,S. demissum Lindl.,S. megistacrolobum Bitt.,S. spegazziniii Bitt. y 5.tarijense Hawkes lo hicieron en el menor grado. Todas las especies probadas restringieron el desarrollo más que el cultivar Kennebec. Las medidas de la tasa de desarrollo larval y de la mortalidad estuvieron correlacionadas con la defoliatión en las pruebas de campo en base s los promedios de los incrementos.en las especies (r=+0,6, P< 01), pero moderadamente correlacionadas en base a los promedios totales de las mismas (r=+0,86, P< 01).

MEASURING RESISTANCE TO THE COLORADO POTATO BEETLE (COLEOPTERA: CHRYSOMELIDAE) IN POTATO

A sensitive test was sought that could be used to detect small differences in resistance to the Colorado potato beetle (CPB) in Solanum species. Three tests were evaluated and compared. One test compared adult CPB foliage consumption of leaf disks from a susceptible potato cv, S. tuberosum, with disks from two S. chacoense clones. The second test compared weight gain on foliage from the three plants by 4th instar larvae and the third test compared larval development rate and mortality. With sufficient replication all three of the tests could detect significant differences between each of the test clones. The most sensitive test measured the stage of development of neonate larvae after feeding on test plants four days. This test required only four replicates to detect a 50% difference from the overall mean assuming an alpha level of 0.05 and a beta level of 0.10.

Early generation selection of insect resistance in potato

Methods used in breeding and selecting potatoes for resistance to Colorado potato beetle, green peach aphid, potato aphid, and potato leafhopper are reviewed. Sources of resistant germplasm, the nature of resistance, breeding behavior of resistance factors, and methods used to measure resistance are discussed. Specific problems encountered in breeding insect-resistant potatoes are discussed in relation to early-generation selection procedures.ResumenSe revisan los métodos usados en mejoramiento y selección de papas para resistencia al escarabajo de papa de Colorado, al áfido verde del duraznero, el áfido de la papa y al satahojas de la papa. Se discuten las fuentes de germoplasma resistente, la naturaleza de la resistencia, comportamiento genético de los factores de resistencia y los métodos usados para medir la resistencia. También se discuten, en relación a los procedimientos de selección en generación temprana, la presencia de problemas específicos que se encuentran en el mejoramiento de papas resistentes a insectos.

Evidence for a Novel Insecticidally Active Exotoxin Produced By the HD 116 Strain of Bacillus thuringiensis var. morrisoni

Liquid chromatographic and bioassay data provide evidence for a novel exotoxin produced by the HD 116 strain of Bacillus thuringiensis var. morrisoni. The exotoxin from HD 116 differs from the well known beta-exotoxin produced by the HD 59 strain of Bacillus thuringiensis var. thuringiensis. Chromatograms of aliquots of filtered fermentation broth taken before and after inoculation with the organisms HD 116 and HD 59 were compared. Based on retention times of the obtained peaks, chromatographic fractions were obtained and activity against first instar larvae of the Colorado potato beetle (Coleoptera: Chrysomelidae) was determined. Fractions based upon similar retention times that were active from var. morrisoni were not active from var. thuringiensis and vice versa. Our conclusion that the new exotoxin may be a diphosphate analog of thuringiensin is based on a comparison of relative retention times among several adenine nucleotides. We have tentatively named this new extracellular exotoxin sigma-exotoxin.

THE INTEGRATION OF A BACTERIUM AND PARASITES TO CONTROL THE COLORADO POTATO BEETLE AND THE MEXICAN BEAN BEETLE

Sprays of Bacillus thuringiensis subsp. thuringiensis (B.t.t.), which contained the beta-exotoxin, were applied to small-scale field plots of tomatoes infested with the Colorado potato beetle [Lept...