66 research outputs found
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Onion Thrips (Thysanoptera: Thripidae) and Their Management in the Treasure Valley of the Pacific Northwest
Onion thrips, Thrips tabaci Lindeman and thrips-transmitted Iris yellow spot virus are the most significant pest complex affecting onion production in the Treasure Valley of eastern Oregon and southwestern Idaho. Thrips feeding damage and virus infection significantly reduce onion bulb size and economic returns for this high value crop. The high concentration of onion fields in the Treasure Valley and the long, hot, dry growing season present a number of challenges for managing onion thrips and Iris yellow spot virus (IYSV). Insecticides are the primary tool that growers have to manage this pest complex. With the long growing season, growers need to exercise good insecticide resistance management programs to maintain the effectiveness of currently available insecticides. To do this, growers need to rotate among available products and use as few applications as practical. A challenge for researchers is to determine not only which insecticides are effective but also to determine when during the season different products may be most effectively used. Techniques for analyzing field trial data are discussed, including comparing changes in pest populations before and after various insecticide applications are made. These comparisons can be made through the use of linear estimates and contrasts as part of analyses of variance, and they can aid in determining efficacy of different treatments by accounting for pre-application populations. These techniques will help researchers in developing sound sequence of insecticide applications for onion thrips management.Keywords:
Yellow Spot Virus,
IPM,
pest management,
analysis of variance,
insecticide resistance management,
Onion thrips,
linear contrast
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Does Temperature-Mediated Reproductive Success Drive the Direction of Species Displacement in Two Invasive Species of Leafminer Fly?
Liriomyza sativae and L. trifolii (Diptera: Agromyzidae) are two highly invasive species of leafmining flies, which have become established as pests of horticultural crops throughout the world. In certain regions where both species have been introduced, L. sativae has displaced L. trifolii, whereas the opposite has occurred in other regions. These opposing outcomes suggest that neither species is an inherently superior competitor. The regions where these displacements have been observed (southern China, Japan and western USA) are climatically different. We determined whether temperature differentially affects the reproductive success of these species and therefore if climatic differences could affect the outcome of interspecific interactions where these species are sympatric. The results of life table parameters indicate that both species can develop successfully at all tested temperatures (20, 25, 31, 33°C). L. sativae had consistently higher fecundities at all temperatures, but L. trifolii developed to reproductive age faster. Age-stage specific survival rates were higher for L. sativae at low temperatures, but these were higher for L. trifolii at higher temperatures. We then compared the net reproductive rates (R₀) for both species in pure and mixed cultures maintained at the same four constant temperatures. Both species had significantly lower net reproductive rates in mixed species cultures compared with their respective pure species cultures, indicating that both species are subject to intense interspecific competition. Net reproductive rates were significantly greater for L. sativae than for L. trifolii in mixed species groups at the lower temperatures, whereas the opposite occurred at the higher temperature. Therefore, interactions between the species are temperature dependent and small differences could shift the competitive balance between the species. These temperature mediated effects may contribute to the current ongoing displacement of L. sativae by the more recent invader L. trifolii in warm climatic areas of China
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Molecular Survey for the Invasive Leafminer Pest Liriomyza huidobrensis (Diptera: Agromyzidae) in California Uncovers Only the Native Pest Liriomyza langei
Liriomyza huidobrensis (Blanchard) is a highly destructive invasive leafminer pest
currently causing extensive damage to vegetable and horticultural crops around the world. Liriomyza
langei Frick is a leafminer pest native to California that cannot currently be morphologically distinguished
from L. huidobrensis. We used a DNA-barcoding approach, a published PCR-RFLP method,
and a new multiplex PCR method to analyze 664 flies matching the morphological description of
huidobrensis-langei. We found no evidence for the presence of L. huidobrensis in our extensive samples
from California. In addition to the new molecular method, this work is important because it provides
definitive data that the California “pea leafminer” is currently, and has probably always been, L. langei.
These data will also be important in the event that the highly invasive L. huidobrensis ever becomes
established.Keywords: molecular diagnostics, crop pest, invasive species, multiplex PC
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Local Crop Planting Systems Enhance Insecticide-Mediated Displacement of Two Invasive Leafminer Fly
Liriomyza sativae and L. trifolii are highly invasive leafminer pests of vegetable crops that have invaded southern China in
recent years. Liriomyza sativae was the first of these species to invade China, but it is now being displaced by L. trifolii. The
rate and extent of this displacement vary across southern China. In Hainan, monocultures of highly valuable cowpea are
planted and treated extensively with insecticides in attempts to control leafminer damage. In Guangdong, cowpea fields are
interspersed with other less valuable crops, such as towel gourd (Luffa cylindrica), which receive significantly fewer
insecticide applications than cowpea. To determine how differences in cropping systems influence the Liriomyza species
composition, we conducted field trials in 2011 and 2012 in Guangdong where both species were present. We replicated
conditions in Hainan by planting cowpea monocultures that were isolated from other agricultural fields, and we replicated
conditions in Guangdong by planting cowpea in a mixed crop environment with towel gourd planted in neighboring plots.
We then compared leafminer populations in cowpea treated with the insecticide avermectin and untreated cowpea. We
also monitored leafminer populations in the untreated towel gourd. Untreated cowpea and towel gourd had comparatively
low proportions of L. trifolii, which remained relatively stable over the course of each season. Avermectin applications led to
increases in the proportions of L. trifolii, and after three weekly applications populations were >95% L. trifolii in both crop
systems. However, the rate of change and persistence of L. trifolii in the mixed crop system were less than in the monocrop.
These results indicate that L. trifolii is much less susceptible to avermectin than is L. sativae. Further, L. sativae was able to
persist in the untreated towel gourd, which probably enabled it to recolonize treated cowpea
Variation within and between Frankliniella Thrips Species in Host Plant Utilization
Anthophilous flower thrips in the genus Frankliniella (Thysanoptera: Thripidae) exploit ephemeral plant resources and therefore must be capable of successfully locating appropriate hosts on a repeated basis, yet little is known of interspecific and intraspecific variation in responses to host plant type and nutritional quality. Field trials were conducted over two seasons to determine if the abundance of males and females of three common Frankliniella species, F. occidentalis (Pergande), F. tritici (Fitch) and F. bispinosa (Morgan), their larvae, and a key predator, Orius insidiosus (Say) (Hemiptera: Anthocoridae) were affected by host plant type and plant nutritional quality. Two host plants, pepper, Capsicum annuum L. (Solanales: Solanaceae) and tomato, Solanum lycopersicum L. that vary in suitability for these species were examined, and their nutritional quality was manipulated by applying three levels of nitrogen fertilization (101 kg/ha, 202 kg/ha, 404 kg/ha). F. occidentalis females were more abundant in pepper than in tomato, but males did not show a differential response. Both sexes of F. tritici and F. bispinosa were more abundant in tomato than in pepper. Larval thrips were more abundant in pepper than in tomato. Likewise, O. insidiosus females and nymphs were more abundant in pepper than in tomato. Only F. occidentalis females showed a distinct response to nitrogen fertilization, with abundance increasing with fertilization. These results show that host plant utilization patterns vary among Frankliniella spp. and should not be generalized from results of the intensively studied F. occidentalis. Given the different pest status of these species and their differential abundance in pepper and tomato, it is critical that scouting programs include species identifications for proper management
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Emergence of Groundnut ringspot virus and Tomato chlorotic spot virus in Vegetables in Florida and the Southeastern United States
Groundnut ringspot virus (GRSV) and Tomato chlorotic spot virus
(TCSV) are two emerging tospoviruses in Florida. In a survey of the
southeastern United States, GRSV and TCSV were frequently detected in
solanaceous crops and weeds with tospovirus-like symptoms in south
Florida, and occurred sympatrically with Tomato spotted wilt virus (TSWV)
in tomato and pepper in south Florida. TSWV was the only tospovirus
detected in other survey locations, with the exceptions of GRSV from tomato
(Solanum lycopersicum) in South Carolina and New York, both of
which are first reports. Impatiens (Impatiens walleriana) and lettuce
(Lactuca sativa) were the only non-solanaceous GRSV and/or TCSV
hosts identified in experimental host range studies. Little genetic diversity
was observed in GRSV and TCSV sequences, likely due to the recent
introductions of both viruses. All GRSV isolates characterized were reassortants
with the TCSV M RNA. In laboratory transmission studies,
Frankliniella schultzei was a more efficient vector of GRSV than F. occidentalis.
TCSV was acquired more efficiently than GRSV by F. occidentalis
but upon acquisition, transmission frequencies were similar. Further
spread of GRSV and TCSV in the United States is possible and detection
of mixed infections highlights the opportunity for additional reassortment
of tospovirus genomic RNAs
Under the Skin of a Lion: Unique Evidence of Upper Paleolithic Exploitation and Use of Cave Lion (Panthera spelaea) from the Lower Gallery of La Garma (Spain)
ABSTRACT: Pleistocene skinning and exploitation of carnivore furs have been previously inferred from archaeological evidence. Nevertheless, the evidence of skinning and fur processing tends to be weak and the interpretations are not strongly sustained by the archaeological record. In the present paper, we analyze unique evidence of patterned anthropic modification and skeletal representation of fossil remains of cave lion (Panthera spelaea) from the Lower Gallery of La Garma (Cantabria, Spain). This site is one of the few that provides Pleistocene examples of lion exploitation by humans. Our archaeozoological study suggests that lion-specialized pelt exploitation and use might have been related to ritual activities during the Middle Magdalenian period (ca. 14800 cal BC). Moreover, the specimens also represent the southernmost European and the latest evidence of cave lion exploitation in Iberia. Therefore, the study seeks to provide alternative explanations for lion extinction in Eurasia and argues for a role of hunting as a factor to take into account
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