Two methods for estimating the tolerance of common beau genotypes to Empoasca kraemeri Ross & Moore were compared, using a yield trial carried out at Centro Internacional de Agricultura Tropical (CIAT), Call, Colombia versus stylet penetration tactics measured by AC electronic feeding monitors. A stylet penetration index was devised based on principal component scores of three penetration tactics identified (pulsing laceration, cell rupturing and lancing sap ingestion), combined with knowledge of the hopperburn symptoms caused by each tactic. Tolerant genotypes, as classified by the CIAT yield index, showed significantly more unprotected yield and lower hopperburn scores than the susceptible control. They also induced performance of less pulsing laceration (the tactic considered most damaging to the plant), lund more of the other two, mitigating tactics, especially cell rupturing. When index: values were calculated for each genotype, stylet penetration index values matched those of the yield index for three out of five genotypes: two EMP-coded tolerant lines ('EMP 385' and 'EMP 392') and die susceptible control 'BAT 41'. Thus, for these three genotypes, all subsequent hopperburn symptoms are predictable by the type of feeding behavior performed on them. 'Porrillo Sintetico' and 'EMP 84', considered borderline genotypes by the yield index, were overestimated and underestimated, respectively, by the stylet penetration index. We postulate that, for these two genotypes, plant physiological responses to feeding (either compensatory or heightened sensitivity respectively) synergize with type of feeding performed to generate the overall hopperburn condition. This multivariate analysis of electronic monitoring data was Successfully used to devise an index of resistance. The implications of using the stylet penetration index and the advantages of using electronic monitoring in a bean-breeding program are discussed.

This study is the first to statistically analyze the stylet probing/penetration behaviors of Lygus (Hemiptera: Miridae) bugs, and the external body movements associated with both probing and nonprobing, via electrical penetration graph (EPG) and videorecording, respectively. Behavioral quantification allows powerful statistical comparisons among host plants or other treatments. Thus, statistical analysis of data has played an important role in EPG research. However, few attempts have been made to standardize types and terminology used for statistical parameters. We provide here the first complete system of organization and terminology for nonsequential EPG parameters. Widespread adoption of these terms will allow standardization in EPG research. Our EPG and video data reveal for the first time the stylet penetration behaviors of nymphal L. hesperus that cause cotton square damage, and the mechanism involved. L. hesperus nymphs spent only 15% of their time on squares probing; the remainder was spent standing motionless in place, grooming, or in sensory exploration. While probing, two thirds of their time was spent in laceration/salivation and one third in ingestion. Thus, L. hesperus nymphs actively spread out numerous, minute injections of their macerating watery saliva, deeply drilled/lacerated into all parts of the developing square. After injection of saliva within the square, the insect then stands and waits for solubilization of the square's cell contents, and then quickly ingests the slurry. The extensive laceration by the stylets may, secondarily, potentiate salivary maceration by mechanically rupturing cell walls. The plant responses to such behavior are thus summarized as "mechanical cell rupture-enhanced maceration."

The effect of nectar-producing plants (Brassica rapa (L.), Calendula officinalis (L.), Ruta graveolens (L.), and Borrago officinalis (L.)), compared to honey solution, on the longevity and fecundity of Diadegma aff. insulare were studied under green house conditions. The longevity and fecundity of D. insulare females fed on B. rapa (L.) were similar to those fed with a solution of honey and water (15,4 +/- 1,1 days, 67,0 +/- 2,7 progeny/female). B. officinalis was the best food source (38,4 +/- 4,6 days, 186,8 +/- 2,5 progeny/female), followed by R. graveolens (18,2 +/- 10,6 days, 91,4 +/- 2,7 progeny). Females fed with C officinalis (4,0 +/- 1,7 days, 12.2 +/- 2,97 progeny) had the lowest fecundity and longevity with respect to the control. The longevity and fecundity of D. insulare varied with morphological characters of flowers. An increase in longevity and fecundity was correlated with a greater width and length of the corolla. In choice and no choice tests, a greater number of flower visits were recorded for R. graveolens (4,2 +/- 1,7 y 5,75 +/- 1,2 visits/min) and B. rapa (3,8 +/- 0,9 y 5,75 +/- 0,9 visits/min). It is suggested that the number of nectar producing plants, especially B. officinalis, be manipulated to increase the impact of D. insulare on the integrated management of P. xylostella.

Se estudió el efecto de plantas productoras de néctar (Brassica rapa (L.), Calendula officinalis (L.), Ruta graveolens (L.), y Borrago officinalis (L.)), comparadas con solución de miel de abejas sobre la longevidad y fecundidad de Diadegma aff. insulare bajo condiciones de casa de malla. La longevidad y fecundidad de hembras de D. aff. insulare alimentadas en B. rapa fueron iguales a las alimentadas con solución de miel y agua (15,4 ± 1,1 días, 67,0 ± 2,7 progenie/hembra). B. officinalis fue la mejor fuente de alimentación (38,4±4,6 días, 186,8±2,5 progenie/ hembra), seguida por R. graveolens (18,2±10,6 días, 91,4±2,7 progenie). Hembras alimentadas con C. officinalis (4,0±1,7 days, 12.2±2,97 progenie) tuvieron la longevidad y fecundidad más baja respecto al testigo. Longevidad y fecundidad variaron con características morfológicas de las flores. Un incremento en longevidad y fecundidad estuvo relacionado con mayor ancho y longitud de corola. En pruebas de selección libre y de no selección se registró un número significativamente mayor de visitas a las flores de R. graveolens (4,2 ±1,7 y 5,75±1,2 visitas/min) y B. rapa (3,8 ± 0,9 y 5,75 ± 0,9 visitas/min). Se sugiere manipular la presencia plantas nectaríferas, especialmente B. officinalis para aumentar el impacto de D. aff. insulare en el manejo integrado de P. xylostella.

Se evaluó el tratamiento cuarentenario T-107-b (1,67 ºC por 22 d) sobre la calidad y vida poscosecha de dos cultivares de feijoa. Se utilizaron los cultivares ‘Cenaf 41’ y ‘Cenaf 8-4’. Los frutos sometidos al tratamiento se compararon con frutos almacenados a 19,0 ºC, simulando transporte y comercialización. Durante el tratamiento se registró la temperatura interna de frutos. Se evaluó el comportamiento fisiológico y químico antes y después del tratamiento. La tasa respiratoria mostró la tendencia de un fruto climatérico. El contenido de sólidos solubles y el pH aumentaron y la acidez titulable disminuyó a través del tiempo. Los frutos con y sin el tratamiento tuvieron un comportamiento poscosecha muy similar en el proceso de comercialización y vida de anaquel.

La mosca suramericana de la fruta Anastrepha fraterculus (Wiedemann) (Díptera: Tephritidae) es una plaga cuarentenaria de la feijoa. Frutas infestadas artificialmente se sometieron al tratamiento “t107-a” (1,1º C durante 15 días) exigido por USDAAPHIS para su exportación y se compararon con frutos almacenados a temperatura ambiente. Cada fruto se infestó con cuatro larvas de tercer instar, en dos tratamientos con 50 repeticiones. Se evaluó diariamente la longitud, el volumen corporal, el comportamiento, la mortalidad y cambios de coloración de las larvas, en una muestra de tres frutos. El primer comportamiento observable de las larvas bajo tratamiento cuarentenario fue el intento de abandonar el fruto. No se observó ninguna variación en la longitud o el volumen corporal de las larvas bajo frío. En el control a temperatura ambiente, las larvas aumentaron de volumen hasta la muda a pupa. El tratamiento en frío modificó el desarrollo larval y la muda larva-pupa. El 100% de las larvas murió ocho días después de estar sometidas al tratamiento de frío. La mayoría de las larvas murieron en un estado intermedio de la muda y presentaron una coloración oscura o “muda parcial”. Bajo el tratamiento cuarentenario el daño a la pulpa no superó el 24%, mientras en el testigo alcanzó el 74%. Este es el primer tratamiento cuarentenario probado para esta plaga en feijoas en Colombia y mostró control total. El cumplimiento de los requisitos cuarentenarios de USDA-APHIS abren el mercado internacional para exportadores colombianos de feijoa.

The South American fruit fly Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) is a quarantine pest of pineapple guava. Artificially infested fruits were subjected to cold treatment t 107a (1.1° C for 15 d), required by USDA-APHIS for exportation and were compared to control fruits maintained at room temperature. Four third-instar larvae were infested per individual fruit in two treatments with 50 replicates. Body length, volume, behavior, mortality and color changes of the larvae were recorded daily in a sample of three fruits. The first behavioral change observed in larvae under cold quarantine treatment was an attempt to abandon the fruits. No variation in body length or volume was observed under the cold quarantine treatment. In the untreated control, larvae increased body volume up to the final molt to pupa. The cold quarantine treatment affected larval development and the larva-pupa All larvae died on the eighth day of cold treatment. Most larvae died while molting to pupa and exhibited a dark coloration or partial molt. Under the cold quarantine treatment, damage to fruits did not exceed 24% where as in the untreated control it reached 74%. This is the first cold quarantine treatment tested for this pest of pineapple guavas in Colombia and it provided total control. Compliance with the quarantine requirements of USDA-APHIS opens the international market for Colombian exporters of pineapple guava.

Hopperburn is a non-contagious disease of plants caused by the direct feeding damage of certain leafhoppers and planthoppers. Although long studied, especially with Empoasca spp. leafhoppers (Cicadellidae: Typhlocybinae), the mechanisms underlying hopperburn have only recently been elucidated. Hopperburn is caused by a dynamic interaction between complex insect feeding stimuli (termed hopperburn initiation) and complex plant responses (termed the hopperburn cascade). Herein we review the nature of the feeding stimuli in hopperburn initiation, especially for Empoasca spp., which we also compare with the planthopper Nilaparvata lugens. Contrary to previous reports, Empoasca hopperburn is not caused solely by toxic saliva. Instead, it is caused by a plant wound response triggered by a unique type of stylet movement, which is then exacerbated by saliva. Electrical penetration graph monitoring has revealed that all Empoasca spp. are cell rupture feeders, not sheath feeders, and that certain tactics of that feeding strategy are more damaging than others. Measuring the proportions of the most damaging feeding led to development of a resistance index, the Stylet Penetration Index, which can predict hopperburn severity in different plants or under different environmental conditions and can supplement or replace traditional, field-based resistance indices.

Two compounds that together constitute the female sex pheromone of the pink hibiscus mealybug (PHM), Maconellicoccus hirsutus, were isolated, identified, and synthesized. They are (R)-2-isopropenyl-5-methyl-4-hexenyl (S)-2-methylbutanoate [common name is (R)-lavandulyl (S)-2-methylbutanoate] and [(R)-2,2-dimethyl-3-(l-methylethylidene)cyclobutyl]methyl (S)-2-methylbutanoate [which we refer to as (R)-maconelliyl (S)-2-methylbutanoate]. Maconelliol is an unusual cyclobutanoid monoterpene, and its structure has been established by enantioselective synthesis from precursors of known structure and configuration. A 1:5 synthetic mixture of the two RS esters (11 mug per rubber septum) proved to be a potent attractant of males in field bioassays. The pheromone component, maconelliyl 2-methylbutanoate, represents a heretofore undescribed natural product.

Biological control programs of Maconellicoccus hirsutus (Green), in the Caribbean have relied on Japanese pumpkins and sprouted potatoes as hosts for rearing both the mealybug and its parasitoids. However, seasonal shortages of these substrates have necessitated that others be found with equal or better qualities for sustaining large mealybug populations. In this paper, we report experiments comparing mass-rearing M. hirsutus on acorn squash (Cucurbita pepo L, var. 'Turbinata'), chayote (Sechium edule [Jacques]), and prickly pear, Opuntia ficus-indica [L.]) with Japanese pumpkin and sprouted potato. In addition, a simple meridic diet based on canned pumpkins was developed and compared. Acorn squash produced large quantities of females (up to 1,300 per squash) with a life cycle and reproductive potential equal to that of mealybugs reared on Japanese pumpkin. Parasitoids reared on these mealybugs developed normally and had a female-biased sex ratio similar to those reared on mealybugs on Japanese pumpkins or potato sprouts. Development of M. hirsutus reared on chayote and prickly pear was delayed by 1.5-5.0 days compared to that of mealybugs reared on Japanese pumpkins. Mealybugs on these substrates produced parasitoids with prolonged developmental times and male-biased sex ratios. On diet, development and reproduction of M. hirsutus was possible only for 3 to 4 consecutive generations. Mealybugs with longer developmental time, lower survival, and smaller ovisacs with lower percentage eclosion were obtained. Parasitoids reared from these mealybugs did not possess desirable characteristics for biological control. The developmental rate of adult parasitoids increased linearly with that of female hosts depending on the quality of the rearing substrate for the mealybugs.

The mealybug Maconellicoccus hirsutus (Green) has extended its range throughout the Caribbean region since it was first detected in Grenada in 1991, and has recently been detected in Southern California, Mexico, and Central America. Laboratory and field experiments using virgin females were conducted on St. Croix, U.S. Virgin Islands, to determine if females attract males with pheromones. Virgin females isolated in gelatin capsules attracted on average one male to each capsule over a period of 18 h in the laboratory compared with gelatin capsules without females. Adhesive traps baited with virgin females and placed on hibiscus, Hibiscus rosa-sinensis L.,in the field, captured more males at all three study localities on St. Croix than did unbaited traps. Virgin females attracted more males than controls at 0-10 m from infested hibiscus, but were capable of attracting males at 50 m distance from an infestation. The attractiveness of virgin females to flying males strongly suggests the involvement of a female-produced sex pheromone. Isolation and synthesis of such a sea pheromone would provide a valuable tool for population monitoring and control of this invasive pest.

Nests of the grass-cutting attine ant Acromyrmex landolti (Forel) were excavated in a lowland tropical savanna in eastern Colombia over a period of 27 mo. Of 135 colonies, nests excavated during the dry season were deeper, had more chambers, and were approximate to 2.5 times larger than those excavated in the same area of native savanna during the wet season. Chambers containing fungus gardens were found to a depth exceeding 2 m during the dry season. During the rainy season, all chambers containing fungus gardens were located within 30 cm of the soil surface. Individual chamber size did not vary seasonally. During the rainy season, colonies relocated to superficial chambers and were smallest in terms of total colony volume and number of chambers per colony. During the dry season, colonies excavated new chambers to depths where soil moisture asymptotically approached a maximum level. Maps of colony location and microtopography of the savanna revealed an aggregated distribution associated with microrelief. Colonies were aggregated on slightly raised ridges that were most likely caused by surface water runoff. Implications for sampling and control are discussed.

Cellular abnormalities induced by the feeding behavior of Empoasca kraemeri Ross & Moore were studied in 2 tolerant lines ('EMP 84' and 'EMP 392'), an intermediate ('Porrillo Sintetico') and a susceptible ('Calima') cultivar of Phaseolus vulgaris L. Groups of two 3- to 4-d-old female leafhoppers were placed for 3 h in 1 clip cage per plant, each covering 1 cm(2) of fully expanded primary leaves, 15 d after planting. Leaf tissues were fixed 48 h after this access period and prepared for light and confocal microscopy. Damage to the leaf lamina in all genotypes included cell emptying and breakage of cell walls, as well as enlarged intercellular spaces in the palisade and spongy parenchyma. In the main vascular bundle, hypertrophied parenchyma cells plus cells with enlarged nuclei and stained nucleoli were observed. In general, cellular damage was less severe in the tolerant lines than in the susceptible genotypes, although more so for EMP 84 than for EMP 392. Morphometry of autofluorescent tracheary elements showed what seems to be a compensatory response to leafhopper attack in the tolerant lines. Although control leaves from tolerant lines had fewer tracheary elements per vascular bundle after leafhopper feeding, EMP 84 had more tracheary elements in damaged tissues. Both tolerant genotypes had tracheary elements with larger internal radii, which increased their estimated relative flow rates. The implications of cellular damage for the onset of hopperburn, in bean as well as other host plants such as alfalfa and potato, and the mechanisms of tolerance are discussed.

Four measures of resistance to the leafcutting ant Acromyrmex landolti (Forel) in 5 forage grasses were evaluated in a neotropical savanna: damage caused by cutting of seedlings during pasture establishment, colonization by A. landolti of established swards, fresh weight of fungus gardens of excavated A. landolti colonies, and ability of the leafcutters' symbiotic fungus to grow on artificial medium containing aqueous extracts of susceptible and resistant grass cultivars. Susceptible forages (Andropogon gayanus 'Carimagua 1' and Brachiaria dictyoneura 'Llanero') had more seedlings cut during establishment and greater colonization by A. landolti in established swards compared with resistant cultivars (B. brizantha 'Marandu, B. decumbens 'Basilisk', and B. humidicola 'Pasto Humidicola'). Fresh weights of the fungus gardens of excavated colonies that had been restricted to cutting resistant cultivars (Paste Humidicola, Marandu or Basilisk) were reduced compared with colonies restricted to Carimagua 1, Llanero, or native savanna (control). Growth of the symbiotic fungus isolated from fungus gardens of A. landolti and Atta laevigata (F. Smith) was reduced when grown on agar with aqueous extracts of resistant cultivars compared with growth of the fungus on agar alone. When cultured on agar with aqueous extract of Carimagua 1, fungus growth was equivalent to the control. Growth of the fungus with homogenate of Llanero was intermediate to control and resistant cultivars. Agreement between these measures of resistance to leafcutting ants and their symbiont indicates that resistance in Brachiaria is conferred by plant factors inhibitory to the symbiotic fungus.

La antibiosis detectada en accesiones del pasto Brachiaria spp. condujo a desarro­llar un sistema de alimentación de insec­tos para estudiar los mecanismos de antibiosis que se expresan sobre varias esp-édes de cercópidos que son los ma­yores limitantes de la producción de pas­tos en América tropical. Se desarrolló una metodología para enraizar tallos de Brachiaria con una solución hidropónica en cilindros de acetato. Las raíces crecie­ron a lo largo del cilindro y atravesaron una cámara donde se ubicó un huevo próximo a eclosionar o una ninfa del cercópido Aeneolamia varia (Fabricius). El cilindro se colocó dentro de un tubo de ensayo de policarbonato, donde se puede suministrar agua o solución nutritiva o cualquier sustancia a probar. La planta toma la solución por las raíces y el insecto la adquiere al alimentarse de los vasos del xilema. Este sistema permite la observa­ción directa y constante de las ninfas durante su desarrollo sin tener que mani­pularlas. Con este sistema, la sobrevivencia de A. varia, de huevo hasta adulto, sobre B. ruziziensis CIAT 654 fue del 100% y la duración de los 5 instares ninfales fue de 33 ± 1,4 días, equivalente a lo obtenido en materos en el invernade­ro. La hormona juvenil (JH-III) administra­da en solución a las raíces no tuvo efecto significativo sobre el insecto. En cambio, la Ecdysona produjo una muda temprana a bajas concentraciones (0,05 -0,5 - 5,0 y 50 ppm) y produjo mortalidad y deforma­ciones a 100 ppm.

Established swards of the tropical forage grass Andropogon gayanus var. bisquamulatus (Hochst.) Hack were heavily colonized by the leaf-cutter Acromyrmex landolti Forel over a period of 33 months in the eastern plains of Colombia. Density of Ac. landolti colonies in swards of A. gayanus increased from 23 +/- 9 at planting in 1988 to 263 +/- 57 colonies per 1800 m2 in 1991. Brachiaria humidicola (Rendle) Schweick was highly resistant to colonization by Ac. landolti. Colony density in swards of B. humidicola declined from 23 +/- 9 at planting in 1988 to 16 +/- 4 colonies per 1800 m2 in 1991. Mean density in adjacent savanna control plots varied over the three years from 114 +/- 23 to 225 +/- 24 colonies per 1800 m2. Maps of colony entrances within swards were made yearly during 1989, 1990, and 1991. Comparison of maps demonstrated that colonies did not persist more than a single year at a given site implying colony migration. Excavation of over 100 colonies of Ac. landolti revealed a single entrance per colony in all cases.

Para establecer la relación existente entre la densidad de hormigueros de Acromyprnex landolti en la sabana nativa antes de la pre­paración del suelo y el éxito en el estableci­miento del Andropogon gayanus se realizó un experimento en "Carim agua", Departa­mento del Meta, en un lote de 2,1 ha (165 x 125 m) con altas poblaciones de la hormiga. Se encontró que en los Llanos la distribución espacial de los hormigueros de A. landolti es en agregados y que se ajusta a la distribución binomial negativa; además se observó que los hormigueros se agrupan en franjas rela­cionadas con la dirección de los canales de escorrentia. Se desarrollo un método de mues­treo sencillo y rápido para estimar la densidad de hormigueros y se determinó que la densi­dad varió de 188 a 1.347 hormigueros/ha y que para lograr el establecimiento de una macolla del pasto por m2, seis meses después de la siembra, no se permite una densidad mayor de 600 hormigueros/ha antes de la pfeparación del suelo.