Ricardo Goenaga

Growth, yield and nutrient uptake of taro grown under upland conditions

Abstract There is a scarcity of basic information on dry matter accumulation by various plant organs, nutrient uptake, and yield of taro [Colocasia esculenta (L.) Schott] grown under upland conditions. These data are essential for the development of technological packages, growth simulation models, and decision support systems designed to promote agrotechnology transfer of the crop in the tropics. Two taro cultivars were planted and harvested for biomass about every six weeks during the growing season. At each harvest, plants were separated into various plant parts and their dry matter and nutrient content were determined. There were no significant differences (P<0.05) in total and edible dry matter content between cultivars. However, cultivar ‘Lila’ absorbed significantly smaller amounts of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and zinc (Zn) than cultivar ‘Blanca’, suggesting that it had a higher nutrient‐use efficiency. Fresh corm yields were not significantly different and averaged...

DRY MATTER PRODUCTION AND LEAF ELEMENTAL CONCENTRATIONS OF RAMBUTAN GROWN ON AN ACID ULTISOL

Little is known about the adaptability of rambutan (Nephelium lappaceum) to highly acidic soils rich in aluminum (Al). A 2-yr field study was conducted to determine the effects of various levels of soil Al on dry matter production, plant growth, and nutrient concentration in the leaves of four cultivars of rambutan. Cultivars and the cultivar x year interaction were not statistically significant for most variables measured in the study. Total, leaf, petiole, stem and root dry weights significantly increased at soil Al concentrations ranging from 0.67 cmol kg−1 to 11.0 cmol kg−1. At this range of soil Al, the concentrations of Al and manganese (Mn) in leaf tissue declined sharply. The results of this study demonstrate that rambutan is highly tolerant to acid soils and that tolerance may involve an Al- and Mn- exclusion mechanism.

Food-Based Lure Performance in Three Locations in Puerto Rico: Attractiveness to Anastrepha suspensa and A. Obliqua (Diptera: Tephritidae)

ABSTRACT Lures based on odors released by hydrolyzed protein were assessed for their attractiveness to Anastrepha obliqua and A. suspensa at 3 locations in Puerto Rico in Aug through Oct 2009. Lures compared included ammonium acetate combined with putrescine, hydrolyzed corn protein (Nulure) with borax, freeze-dried Nulure, freeze-dried Nulure in combination with ammonium acetate, freeze-dried Nulure in combination with ammonium acetate and putrescine, and the Unipak lure, a single lure containing ammonium acetate and putrescine. Where the distribution of trapped flies departed significantly from what would be expected given an equal attraction of the baits, Nulure and freeze-dried Nulure always attracted fewer flies than the other baits tested, regardless of species, sex, or location. Although all of the baits or bait combinations containing ammonium acetate attracted more flies than the Nulure or freeze-dried Nulure baits, there was a distinct trend of ammonium acetate and putrescine and the Unipak lures to attract more flies after the 4th week of the study and for the freeze-dried Nulure with ammonium acetate or in combination with ammonium acetate and putrescine to attract more flies in the 1st 4 weeks of the study. This trial is unique in that it was conducted in orchards of carambola, Averrrhoa carambola (Oxalidaceae), a poor host for both fly species. Our results are compared with other studies on lures of A. obliqua and A. suspensa and the implications for monitoring/detecting pest Tephritidae are discussed.

Host Breadth and Parasitoids of Fruit Flies (Anastrepha spp.) (Diptera: Tephritidae) in Puerto Rico

Abstract Twenty fruit species representing 12 families were collected from various regions in western Puerto Rico and monitored for the emergence of Anastrepha spp. pupae. We collected 14,154 tephritid pupae from 16 fruit species representing 10 families. The relative infestations of these fruits (pupae per kilogram of fruit) were recorded. Recorded host ranges were not in complete agreement with those reported in the literature. This host-use pattern should give pause to regulators of fruit importation and exportation that base their decisions on literature from regions other than those of immediate interest to them. We recovered the braconid parasitoid Utetes anastrephae (Viereck) from tephritid pupae collected from Mangifera indica L., Spondias mombin L., Psidium guajava L., Chrysobalanus icacos L., Terminalia catappa L., and Garcinia intermedia (Pittier) Hammel. We collected one specimen of the parasitoid Doryctobracon aerolatus (Szepligeti) from the west coast (Añasco), which had not been previously reported in Puerto Rico. We present a preliminary phenology of what are probably the primary fruit hosts of the Anastrepha spp. of Puerto Rico. We also present the first report of Garcinia intermedia (Pittier) Hammel and Coffea arabica L. as reproductive hosts of A. suspensa.

HOST STATUS OF MAMEY SAPOTE, POUTERIA SAPOTA (SAPOTACEAE), TO THE WEST INDIAN FRUIT FLY, ANASTREPHA OBLIQUA (DIPTERA: TEPHRITIDAE) IN PUERTO RICO

Abstract The authors evaluated the host status of mamey sapote, Pouteria sapota (Sapotaceae) to Anastrepha obliqua by collecting mature fruits and monitoring them for the emergence of larval Tephritidae. Fruits were also scarred and placed in cages with female A. obliqua and monitored for the emergence of larvae and adults. Multi-lure traps baited with putrescine and ammonium acetate were used to compare the number of flies in orchards of mamey sapote to the number of flies in nearby orchards of carambola (Averrhoa carambola: Oxalidaceae). There are a number of references citing mamey sapote as a host of A. obliqua in different countries. However, we only found two unidentified tephritid larva from 1,160 mamey sapote fruits collected in the field and these fly larvae did not survive to adulthood. We were not able to rear adult A. obliqua on scarred, mature fruit of mamey sapote, whereas we were able to do so on mango under identical conditions. Abundance in orchards based on trapping indicates that flies are very rarely encountered in orchards of mamey sapote compared with orchards of carambola. We conclude that in Puerto Rico mamey sapote has a very low (undetectable) rate of infestation by fruit flies in the family Tephritidae.

Rapid evaluation of juvenile sorghum for tolerance to soil acidity

Abstract Sorghum (Sorghum bicolor L. Moench) is a versatile drought‐tolerant crop; part of its potential for expansion in the subtropics of the US and the tropics is unrealized because of its sensitivity to soil acidity. Improved methods for rapid evaluation of acid soil tolerance may help breeding programs to overcome this limitation. Four‐day root growth of seedlings of six genotypes in rapid tests in acid soil media was significantly correlated (R2 = 0.82) with acid soil tolerance evaluated in a field experiment on a high‐Al Ultisol in Corozal, Puerto Rico. This indicates that the ability of the roots of tolerant genotypes to penetrate into acid environments was a key aspect of their success in the field. A solution culture test showed that aluminum (Al) was the principal acidity factor in the acid soil at Corozal. Rapid seedling root growth tests can non‐destructively identify plants having genetic potential to withstand Al toxicity in the field and increase the efficiency of breeding programs.

ANTENNAL RESPONSES OF WEST INDIAN AND CARIBBEAN FRUIT FLIES (DIPTERA: TEPHRITIDAE) TO AMMONIUM BICARBONATE AND PUTRESCINE LURES

ABSTRACT Efforts to monitor and detect tephritid fruit flies in the genus Anastrepha currently involve MultiLure traps baited with two food-based synthetic attractants, ammonia (typically formulated as ammonium acetate or ammonium bicarbonate) and putrescine (1,4-diaminobutane). These baits are used in Central America, Florida, Texas, and the Caribbean to target/capture economically important Anastrepha spp. within each region. The efficacy of these baits varies by region and by species. Antennal responses to these compounds have been quantified for A. suspensa populations in Florida, but not elsewhere. This is the first report of antennal responses of Puerto Rican populations of A. obliqua and A. suspensa to the bait odors emitted from ammonium bicarbonate and putrescine lures. Responses to lure volatiles (tested separately and in combination), as measured by electroantennography (EAG), were dose dependant for both species and both sexes. Although the average response to ammonium bicarbonate in combination with putrescine was always numerically higher than responses to ammonium bicarbonate alone within a species and a sex, this result was never statistically significant. Males of A. obliqua were less sensitive than females, while males of A. suspensa were more sensitive than females to all volatiles and volatile mixtures, but these differences were not statistically significant at any dose. Female A. obliqua were more sensitive than A. suspensa females at all doses for all volatiles and all volatile mixtures, and these differences were statistically significant at the two highest doses of ammonium bicarbonate and ammonium bicarbonate plus putrescine. Our results are broadly similar with the electrophysiological studies conducted on Florida populations of A. suspensa, but there are important differences, most notably that the Florida study detected significantly lower responses by males than females to putrescine and ammonium bicarbonate plus putrescine. The implications of our results are discussed with respect to monitoring practices in different regions.

Efficacy of Entomopathogenic Nematodes Versus Diaprepes abbreviatus (Coleoptera: Curculionidae) Larvae in a High Clay-Content Oxisol Soil: Greenhouse Trials With Potted Litchi chinensis

Abstract In a previous study, laboratory trials indicated that 9 strains and species of entomopathogenic nematodes (EPNs) were pathogenic against larvae of Diaprepes abbreviatus in an Oxisol from Puerto Rico. In this study we tested the efficacy of 5 species/strains of EPN in an Oxisol under greenhouse conditions. The nematodes were applied at 100 infective juveniles per cm2 to 19-L pots containing a high clay-content Oxisol (69% clay) and 3 seedlings of Litchi chinensis. All treatments significantly reduced the mean proportion of D. abbreviatus larvae surviving (ranging from 0 to 36%) compared to survival in untreated controls (ranging from 80 to 86%). This suggests that EPNs might be suitable to play a role in integrated pest management strategies against D. abbreviatus in tropical soils with high clay content.

Diaphorina citri (Hemiptera: Liviidae) Abundance in Puerto Rico Declines with Elevation

ABSTRACT Diaphorina citri Kuwayama is the primary vector of Huanglongbing, the most devastating disease of citrus. D. citri populations in Puerto Rico were monitored with yellow sticky traps on citrus trees or other psyllid host plants at different elevations, ranging from 10 to 880m above sea level. Trapping was conducted in March through May of 2013 and 2014 when psyllid populations usually are highest. Population levels of D. citri, based on the trapping data, varied among the sites, and there was a strong trend in both years for decreasing psyllid abundance with increased elevation based on the number of psyllids captured on traps and the proportion of trees shown to be infested. No psyllids were collected at an elevation of >600 m. Reduced populations at higher elevations could be a consequence of differences in temperature, air pressure, oxygen levels, ultraviolet light, or other factors alone or in combination. We discuss our results as they pertain to management of D. citri and Huanglongbing.

Host Status of Litchi and Rambutan to the West Indian Fruit Fly (Diptera: Tephritidae)

Abstract Fruit of litchi, Litchi chinensis, and rambutan, Nephelium lappaceum, were collected from the field in 2006 and 2007 and monitored for the emergence of West Indian fruit flies, Anastrepha obliqua. Fruit clusters of rambutan and litchi, with a piece of the peel removed to allow access to ovipositing females, were also placed in cages and exposed to 12-d-old post-eclosion male and female West Indian fruit flies for 48 h. These exposed fruit were then monitored for the emergence of A. obliqua. Mango fruit were simultaneously exposed to male and female A. obliqua in separate cages and monitored for the emergence of A. obliqua. Fruit fly traps baited with putrescine and ammonium acetate were placed in orchards of litchi and rambutan, as well as an adjacent orchard of carambola, Averrhoa carambola, to demonstrate the presence of fruit flies while litchi and rambutan were fruiting. Although we collected 3732 ripe litchi fruit (40.34 kg) and 5534 ripe rambutan fruit (166.60 kg), none of these yielded tephritid larvae. Litchi and rambutan fruit exposed to adult fruit flies in cages did not yield tephritid larvae, though similarly exposed mangoes did. We conclude that litchi and rambutan have an undetectably low probability of being infested by A. obliqua in Puerto Rico.