Mark E. Whalon

The Tomato Homolog of CORONATINE-INSENSITIVE1 Is Required for the Maternal Control of Seed Maturation, Jasmonate-Signaled Defense Responses, and Glandular Trichome Development

Jasmonic acid (JA) is a fatty acid–derived signaling molecule that regulates a broad range of plant defense responses against herbivores and some microbial pathogens. Molecular genetic studies in Arabidopsis have established that JA also performs a critical role in anther and pollen development but is not essential for other developmental aspects of the plants life cycle. Here, we describe the phenotypic and molecular characterization of a sterile mutant of tomato (jasmonic acid–insensitive1 [jai1]) that is defective in JA signaling. Although the mutant exhibited reduced pollen viability, sterility was caused by a defect in the maternal control of seed maturation, which was associated with the loss of accumulation of JA-regulated proteinase inhibitor proteins in reproductive tissues. jai1 plants exhibited several defense-related phenotypes, including the inability to express JA-responsive genes, severely compromised resistance to two-spotted spider mites, and abnormal development of glandular trichomes. We demonstrate that these defects are caused by the loss of function of the tomato homolog of CORONATINE-INSENSITIVE1 (COI1), an F-box protein that is required for JA-signaled processes in Arabidopsis. These findings indicate that the JA/COI1 signaling pathway regulates distinct developmental processes in different plants and suggest a role for JA in the promotion of glandular trichome–based defenses.

Managing Insect Resistance to Bacillus thuringiensis Toxins

Bacillus thuringiensis (B.t.) δ-endotoxins provide an alternative to chemical insecticides for controlling many species of pest insects. Recent biotechnological developments offer the promise of even greater use of B.t. toxins in genetically transformed pest-resistant crops. However, the discovery that insects can adapt to these toxins raises concerns about the long-term usefulness of B.t. toxins. Several methods for managing the development of resistance to B.t. toxins have been suggested, but none of these approaches offer clear advantages in all situations.

Global pesticide resistance in arthropods.

Global pesticide resistance in arthropods , Global pesticide resistance in arthropods , کتابخانه دیجیتال جندی شاپور اهواز

Behavioral and Electrophysiological Responses of Leafroller Moths to Selected Plant Extracts

Abstract The behavioral and electrophysiological responses of the obliquebanded leafroller, Choristoneura rosaceana (Harris), and the redbanded leafroller, Argyrotaenia velutinana (Walker), to crude extracts of Arctium lappa, Bifora radians, Humulus lupulus, Xanthium strumarium, and Verbascum spp. were studied under laboratory conditions. Plant materials were dried and ground before extraction with methanol. Plant extract residues were mixed in acetone to give 20% (wt:wt) suspensions after evaporation of excess methanol. All five plant extracts elicited significant electroantennogram (EAG) responses from both males and females of each species. EAG responses to X. strumarium were generally the highest for both species. The behavioral responses of male and female obliquebanded leafrollers to the plant extracts were compared with responses to pheromone [(Z)11–14:Ac] and a solvent control. Significantly more male and female obliquebanded leafrollers were attracted to X. strumarium compared with pheromone on filter paper, H. lupulus, Verbascum spp., and the control. Compared with the control, there was no significant attraction to pheromone on filter paper, A. lappa, H. lupulus, and Verbascum spp. The oviposition-deterring effect of plant extracts on female obliquebanded leafrollers was studied in dual-choice bioassays. B. radians elicited the highest oviposition deterring effect with no eggs laid on this treatment. A. lappa was also effective and reduced oviposition to 2.9% of that observed in the controls. The number of eggs laid on X. strumarium (14.4%) and Verbascum spp. (21.2%) treatments were not significantly reduced relative to the control; however, oviposition was reduced by three-fold by these two treatments. The results show that certain crude plant extracts induce behavioral effects on male and female obliquebanded leafrollers. Further studies are needed to determine the active ingredients and their potential use in pest management strategies aimed at managing these pest species in tree fruit production.

Contact and residual toxicities of 30 plant extracts to Colorado potato beetle larvae

Abstract Contact and residual toxicities of 30 plant extracts were investigated on third instar larvae of Colorado potato beetle, Leptinotarsa decemlineata. The plant samples were collected during the spring and summer of 2002 and were dried and ground. The plant samples were treated with methanol and the residue was eluted with distilled water containing 10% acetone, resulting in plant extracts. In contact bioassays, the beetle larvae were treated with 40% (w/w) plant extract using a Potter Spray Tower. The insects were incubated at 28±2°C under a 16 h: 8 h photo regime and the mortality was recorded at 24 h intervals for 7 days. The plant extracts exhibited varying toxicity to the larvae ranging from 0 – 91% after 24 h incubation and Artemisia vulgaris, Hedera helix, Humulus lupulus, Lolium temulentum, Rubia tinctoria, Salvia officinalis, Sambucus nigra, Urtica dioica, Verbascum songaricum, and Xanthium strumarium extracts resulted in significantly higher mortality than the control. Generally, prolonged incubation time did not result in an increase in mortality. After 48 h of incubation, 10 plant extracts yielded a significant mortality and H. lupulus extract, the most toxic extract among those tested, caused 99% mortality which is similar the mortality caused by the chemical standard, imidacloprid. In residual assays, potato leaflets were treated with 20% (w/w) plant-extract concentrations using a Potter Spray Tower. Third instar larvae were added to a glass jar to which treated leaflets were transferred before incubation at the temperature and photo regime described above. Mortality was recorded at 24 h intervals for 7 days. Five plant extracts, H. lupulus, L. temulentum, Reseda lutea and Solanum nigrum, induced significantly higher mortalities compared with controls. Chenopodium album extract was the most toxic, killing 34.9% of exposed larvae, followed by L. temulentum, H. lupulus and S. nigrum after 72 h incubation. The results exhibited that certain plant extracts were toxic to the beetle larvae and may have potential for controlling this destructive pest under field conditions.

Bacillus thuringiensis resistant colorado potato beetle and transgenic plants: Some operational and ecological implications for deployment

The Colorado potato beetle is a severe pest of potatoes in the US. It has developed field resistance to almost every insecticide used against it, and is considered to be a model species for insecticide resistance. We have recently reported the selection of a Bacillus thuringiensis (Bt) resistant strain of beetle (Bt‐R). We have tested this strain and susceptible beetles (Bt‐S) against transgenic potato plants in 96‐h (first instars through adults) and complete development bioassays (second instars through adults). The Bt‐R strain first instars were almost as susceptible to transgenic plants as the Bt‐S strain, but second instars were significantly different from controls in longevity and weight gained (P<0.01). Adult Bt‐R beetles averaged 25% mortality over 14 days, and each of the younger instars (fourth, third and second) experienced greater mortality. The operational and ecological implications of potential Bt resistance on deployment of transgenic potato plants are discussed.

A Systems Approach to IPM Integration, Ecological Assessment and Resistance Management in Tree Fruit Orchards

Twentieth century Integrated Pest Management (IPM) was indisputably marked by the dominance of organophosphate (OP) insecticides for pest control in U.S., European, and Australasia specialty crop production (Perry et al. 1998, Ware and Whitecre 2004). Even though this early IPM period brought forth the concepts of economic thresholds, and robust pest monitoring and modeling (i.e. synthetic pheromones, traps, computers, systems engineering, etc.), once a control action was deemed necessary, the application of a lethal agent to kill the target pest followed before injury could occur (Metcalf 1980). This approach was successful in part because most conventional broad-spectrum insecticides, regardless of chemical class, carried a similar set of performance attributes, as all were fast-acting contact nerve poisons. Thus, the success of the organophosphates, carbamates and synthetic pyrethroids led to a narrow concept of pest control, and reduced the perceived need for scientific investigation for anything beyond the determination of acute toxic effects of insecticides on the target pest and beneficials. One notable exception to this concept was the emergence of pheromone-mediated control, which provided important new avenues in specialty crop IPM beyond chemical control tactics, and is likely to have expanded application in the twenty-first century (Gut et al. 2004).

Toxicity and Antifeedant Activity of Selected Plant Extracts Against Larval Obliquebanded Leafroller, Choristoneura rosaceana (Harris)

Several plant extracts were evaluated against obliquebanded leafroller larvae to determine potential toxicity and antifeedant effects. Two of the plant extracts exhibited contact toxicity; the LC50 value of Humulus lupulus extract against 3 rd insar larvae was 24.5 μg / insect. In a no choice context, larval survivorship was reduced 23 - 57 % after feeding on a meridic pinto bean diet treated with the extracts. Furthermore, average female and male pupal weight was reduced for lea- frollers that fed on diet treated with each of the individually-tested extracts at a 4 % concentration (w/w). Incorporation of Bifora radians and H. lupulus into diet deterred larval feeding at a 1 % concentration by weight. H. lupulus and Arctium lappa extracts were deleterious to larvae in each of the bioassay methods conducted, exhibiting toxic, developmental, and antifeedant effects. These two extracts may be promising candidates for further development as botanical insecticides that could potentially substitute broad-spectrum synthetic neurotoxins for leafroller control.

Field Efficacy of Entomopathogenic Fungi and Nematodes Targeting Caged Last-Instar Plum Curculio (Coleoptera: Curculionidae) in Michigan Cherry and Apple Orchards

ABSTRACT The plum curculio (Conotrachelus nenuphar Herbst) is a key pest of pome and stone fruit in eastern North America. We tested the efficacy of five pathogens over the course of three seasons in 10 Michigan apple and cherry orchards, with introductions of larvae to caged pots containing pathogen-treated soil. The nematode Steinernema riobrave was the most effective pathogen in the 2 yr it was tested, but only in soils with the highest sand content (81–88%) and when it was applied 1 h or 5 d after last instars of plum curculio. S. carpocapsae in an organic formulation was less effective, but significantly reduced plum curculio emergence in 1 yr of the study when applied 3 d before C. nenuphar larvae were introduced. Beauveria bassiana was effective in only 1 of the 3 yr it was tested, only in soils with lower sand content, and only when it was introduced within 1 h of plum curculio larvae. Metarhizium anisopliae and Heterorhabditis bacteriophora were ineffective. Michigan orchards may require sprinkler irrigation coupled with precise timing recommendations and oviposition monitoring to enhance entomopathogen application efficacy against soil-dwelling last instars.

Hydrolysis of permethrin by pyrethroid esterases from resistant and susceptible strains of Amblyseius fallacis (Acari: Phytoseiidae)☆

Abstract Pyrethroid-hydrolyzing activity in whole body homogenates of three insecticide-resistant and one susceptible strain of the predator mite, Amblyseius fallacis Garman has been examined in vitro . The highest esterase activity was found in the synthetic pyrethroid-resistant GH-1 strain body homogenate. All three pyrethroid-resistant strains had esterases that hydrolyzed trans -permethrin two times faster than cis -permethrin but isomer specificity was not observed in the susceptible strain. The pyrethroid esterases of the GH-1 strain were very sensitive to inhibition by dichlorovos, S,S,S -tributhylphosphorotrithioate, and 3-octylthio-1,1,1-trifluoro-2-propanone. Carbaryl and tetraethylpyrophosphate exhibited moderate inhibition in the GH-1 strain. Eserine sulfate and piperonyl butoxide only inhibited permethrin hydrolysis at higher concentrations. Fifteen esterase bands were resolved from body homogenates by gradient gel electrophoresis in the GH-1 strain, and were identified as carboxylesterases. The major pyrethroid-hydrolyzing activity was located in E5–E12 bands from GH-1 and composite susceptible strain esterases. Six esterase bands exhibiting low pyrethroid-hydroloyzing activity were also obtained from the two spotted spider mite, Tetranychus urticae (Koch).