Organic Treatments for Control of Pepper Weevil (Coleoptera: Curculionidae)

The pepper weevil, Anthonomus eugenii Cano (Coleoptera: Curculionidae) is a major pest of pepper (Capsicum spp.; Solanales: Solanaceae) in the southern United States, Mexico, Central America and the Caribbean. Feeding and oviposition cause flower and fruit abscission and internal fruit damage resulting in serious yield losses. Females lay eggs in flower buds and small fruits, shielding larvae from contact pesticides, leaving only the adult stage vulnerable. The purpose of this study was to investigate low-risk and organic products for use against the pepper weevil to provide both organic and conventional growers with more control options. A neem product (Ecozin® 1.2% ME), kaolin clay (Surround® WP), diatomaceous earth (Red Lake Earth®) and a product based on plant terpenes (Requiem®), were tested in lab and field trials for efficacy against pepper weevil. The neem product did not reduce feeding or oviposition in lab choice and no choice tests, so it was not tested in the field. Kaolin clay, diatomaceous earth and Requiem reduced feeding and oviposition in lab trials. Spring and fall field tests of these products were conducted in small plots along with a standard pesticide rotation of Actara and Vydate and an untreated control. The only treatment to increase marketable yield was the standard pesticide rotation. In the spring field trial, the standard treatment doubled yield per plant compared to the untreated controls but the yield was not different from those in the kaolin clay and surround plots. While the organic products did not increase marketable yield significantly, they did decrease overall damage, indicating possible usefulness in combination with conventional insecticides or in low population pressure by spraying early and following appropriate cultural practices such as adequate fallow periods and crop destruction. We recommend further testing of diatomaceous earth in particular in combination with conventional and organic insecticides as part of future IPM program research

Waveform Library for Chinch Bugs (Hemiptera: Heteroptera: Blissidae): Characterization of Electrical Penetration Graph Waveforms at Multiple Input Impedances

Electrical penetration graph (EPG) monitoring has been used extensively to elucidate mechanisms of resistance in plants to insect herbivores with piercing-sucking mouthparts. Characterization of waveforms produced by insects during stylet probing is essential to the application of this technology. In the studies described herein, a four-channel Backus and Bennett AC-DC monitor was used to characterize EPG waveforms produced by adults of two economically important chinch bug species: southern chinch bug, Blissus insularis Barber, feeding on St. Augustinegrass, and western chinch bug, Blissus occiduus Barber, feeding on buffalograss. This is only the third time a heteropterans species has been recorded by using EPG; it is also the first recording of adult heteropterans, and the first of Blissidae. Probing of chinch bugs was recorded with either AC or DC applied voltage, no applied voltage, or voltage switched between AC and DC mid-recording, at input impedances ranging from 106 to 1010Ω, plus 1013 Ω, to develop a waveform library. Waveforms exhibited by western and southern chinch bugs were similar, and both showed long periods of putative pathway and ingestion phases (typical of salivary sheath feeders) interspersed with shorter phases, termed transitional J wave and interruption. The J wave is suspected to be an X wave, that is, in EPG parlance, a stereotypical transition waveform that marks contact with a preferred ingestion tissue. The flexibility of using multiple input impedances with the AC-DC monitor was valuable for determining the electrical origin (resistance vs. electromotive force components) of the chinch bug waveforms. It was concluded that an input impedance of 107Ω, with either DC or AC applied voltage, is optimal to detect all resistance- and electromotive force–component waveforms produced during chinch bug probing. Knowledge of electrical origins suggested hypothesized biological meanings of the waveforms, before time-intensive future correlation experiments by using histology, microscopy, and other techniques

Waveform Library for Chinch Bugs (Hemiptera: Heteroptera: Blissidae): Characterization of Electrical Penetration Graph Waveforms at Multiple Input Impedances

Electrical penetration graph (EPG) monitoring has been used extensively to elucidate mechanisms of resistance in plants to insect herbivores with piercing-sucking mouthparts. Characterization of waveforms produced by insects during stylet probing is essential to the application of this technology. In the studies described herein, a four-channel Backus and Bennett AC-DC monitor was used to characterize EPG waveforms produced by adults of two economically important chinch bug species: southern chinch bug, Blissus insularis Barber, feeding on St. Augustinegrass, and western chinch bug, Blissus occiduus Barber, feeding on buffalograss. This is only the third time a heteropterans species has been recorded by using EPG; it is also the first recording of adult heteropterans, and the first of Blissidae. Probing of chinch bugs was recorded with either AC or DC applied voltage, no applied voltage, or voltage switched between AC and DC mid-recording, at input impedances ranging from 106 to 1010Ω, plus 1013 Ω, to develop a waveform library. Waveforms exhibited by western and southern chinch bugs were similar, and both showed long periods of putative pathway and ingestion phases (typical of salivary sheath feeders) interspersed with shorter phases, termed transitional J wave and interruption. The J wave is suspected to be an X wave, that is, in EPG parlance, a stereotypical transition waveform that marks contact with a preferred ingestion tissue. The flexibility of using multiple input impedances with the AC-DC monitor was valuable for determining the electrical origin (resistance vs. electromotive force components) of the chinch bug waveforms. It was concluded that an input impedance of 107Ω, with either DC or AC applied voltage, is optimal to detect all resistance- and electromotive force–component waveforms produced during chinch bug probing. Knowledge of electrical origins suggested hypothesized biological meanings of the waveforms, before time-intensive future correlation experiments by using histology, microscopy, and other techniques

Aggregation Behavior of the Southern Chinch Bug (Hemiptera: Blissidae)

The southern chinch bug, Blissus insularis Barber, forms dense, multigenerational aggregations in St. Augustinegrass lawns leading to grass death from sap feeding. We conducted laboratory bioassays to better understand the signals responsible for the formation and maintenance of southern chinch bug aggregations. In small arena assays, chinch bugs demonstrated a stronger aggregation response over time and aggregated more often on or beneath St. Augustinegrass leaf blades than on or under artificial leaf-like shelters constructed from white or green paper. In Y-tube olfactometer assays, bugs of different age and sex were attracted to volatiles from mixed-sex chinch bug aggregations and showed particular attraction to groups of adult female chinch bugs. Adult males and nymphs were also attracted to adult males. Nymphs were attracted to nymphs and were also more attracted to aggregation volatiles when they could see bugs in the arm of the Y-tube. Adult males were more attracted to short-winged than long-winged adults, while females and nymphs demonstrated no preference. All bugs were attracted to St. Augustinegrass volatiles when presented alone, but only males preferred the odor of grass over odor released from a chinch bug mixed-sex aggregation. When presented with a choice of grass and grass + aggregation volatiles, males preferred the combined treatment. The results of these assays suggest that a complex combination of life stage, sex, as well as plant and insect-derived signals influence chinch bug aggregation behavior

Aggregation Behavior of the Southern Chinch Bug (Hemiptera: Blissidae)

The southern chinch bug, Blissus insularis Barber, forms dense, multigenerational aggregations in St. Augustinegrass lawns leading to grass death from sap feeding. We conducted laboratory bioassays to better understand the signals responsible for the formation and maintenance of southern chinch bug aggregations. In small arena assays, chinch bugs demonstrated a stronger aggregation response over time and aggregated more often on or beneath St. Augustinegrass leaf blades than on or under artificial leaf-like shelters constructed from white or green paper. In Y-tube olfactometer assays, bugs of different age and sex were attracted to volatiles from mixed-sex chinch bug aggregations and showed particular attraction to groups of adult female chinch bugs. Adult males and nymphs were also attracted to adult males. Nymphs were attracted to nymphs and were also more attracted to aggregation volatiles when they could see bugs in the arm of the Y-tube. Adult males were more attracted to short-winged than long-winged adults, while females and nymphs demonstrated no preference. All bugs were attracted to St. Augustinegrass volatiles when presented alone, but only males preferred the odor of grass over odor released from a chinch bug mixed-sex aggregation. When presented with a choice of grass and grass + aggregation volatiles, males preferred the combined treatment. The results of these assays suggest that a complex combination of life stage, sex, as well as plant and insect-derived signals influence chinch bug aggregation behavior

THE EFFECTS OF SILICA FERTILIZER AS AN ANTI-HERBIVORE DEFENSE IN CUCUMBER

This study aims to improve our understanding of silicon"s role in deterring herbivores from Cucumissativa. We hypothesized that silicon"s role in plant defense is due to the presence of silica augmenting other physical and/or chemical defenses used by the plant. Using C. sativa plants treated with either a silica fertilizer treatment (Si+) or a control solution (Si-), we monitored feeding preferences of two types of her- bivores, a chewing herbivore (Diabrotica balteata) and a piercing/sucking herbivore (Bemisia tabaci). Leaves from treatment plants were visited less and eaten less than leaves from control plants. We then assessed the differences in physical defenses by comparing the leaf structural components, nutrient and water content, and trichome density between treatment and control plants. For chemical plant defenses, we measured leaf carbon and nitrogen levels in, and volatile organic compounds (VOCs) from treatment and control plants. We found no significant difference between treatment and control plants in: lignin content, most elemental plant nutrients, water content, trichome density, and quantity of carbon and nitrogen. We did see an increase in the VOC Indole, known for plant defense priming, an increase in phosphorous levels and a decrease in cellulose levels in silica treated plants

Interactive Effects of Elevated [CO2] and Drought on the Maize Phytochemical Defense Response against Mycotoxigenic Fusarium verticillioides.

Changes in climate due to rising atmospheric carbon dioxide concentration ([CO2]) are predicted to intensify episodes of drought, but our understanding of how these combined conditions will influence crop-pathogen interactions is limited. We recently demonstrated that elevated [CO2] alone enhances maize susceptibility to the mycotoxigenic pathogen, Fusarium verticillioides (Fv) but fumonisin levels remain unaffected. In this study we show that maize simultaneously exposed to elevated [CO2] and drought are even more susceptible to Fv proliferation and also prone to higher levels of fumonisin contamination. Despite the increase in fumonisin levels, the amount of fumonisin produced in relation to pathogen biomass remained lower than corresponding plants grown at ambient [CO2]. Therefore, the increase in fumonisin contamination was likely due to even greater pathogen biomass rather than an increase in host-derived stimulants. Drought did not negate the compromising effects of elevated [CO2] on the accumulation of maize phytohormones and metabolites. However, since elevated [CO2] does not influence the drought-induced accumulation of abscisic acid (ABA) or root terpenoid phytoalexins, the effects elevated [CO2] are negated belowground, but the stifled defense response aboveground may be a consequence of resource redirection to the roots

Interactive Effects of Elevated [CO2] and Drought on the Maize Phytochemical Defense Response against Mycotoxigenic Fusarium verticillioides.

Changes in climate due to rising atmospheric carbon dioxide concentration ([CO2]) are predicted to intensify episodes of drought, but our understanding of how these combined conditions will influence crop-pathogen interactions is limited. We recently demonstrated that elevated [CO2] alone enhances maize susceptibility to the mycotoxigenic pathogen, Fusarium verticillioides (Fv) but fumonisin levels remain unaffected. In this study we show that maize simultaneously exposed to elevated [CO2] and drought are even more susceptible to Fv proliferation and also prone to higher levels of fumonisin contamination. Despite the increase in fumonisin levels, the amount of fumonisin produced in relation to pathogen biomass remained lower than corresponding plants grown at ambient [CO2]. Therefore, the increase in fumonisin contamination was likely due to even greater pathogen biomass rather than an increase in host-derived stimulants. Drought did not negate the compromising effects of elevated [CO2] on the accumulation of maize phytohormones and metabolites. However, since elevated [CO2] does not influence the drought-induced accumulation of abscisic acid (ABA) or root terpenoid phytoalexins, the effects elevated [CO2] are negated belowground, but the stifled defense response aboveground may be a consequence of resource redirection to the roots