Optimization of 13-tetradecenyl acetate sex pheromone for trapping Melanotus communis (Coleoptera: Elateridae).

Corn wireworm, Melanotus communis Gyllenhal (Coleoptera: Elateridae), is an economically important larval pest of root and tuber crops in the United States. Previous work to estimate field-level abundance of M. communis has focused on grain-based larval baits placed in soil. However, this sampling method is labor intensive and may not estimate population size accurately. Recent discovery of the M. communis sex pheromone, 13-tetradecenyl acetate, provides a new method to monitor this pest during the adult stage. Early studies with this pheromone showed that different trapping methods might enhance catch and improve trap servicing. We hypothesized that placing lures on elevated traps would increase M. communis capture relative to the in-ground pitfall trapping that is currently used. We had 2 objectives for this study: (a) to compare pheromone captures among in-ground pitfall traps, on-ground pitfalls, elevated pitfalls (1 m), or elevated sticky cards (1 m) and (b) test lure longevity by aging the lures outdoors at 8-, 6-, 4-, 2-, and 0-wk intervals prior to trap deployment in the field. Experiments were conducted in North Carolina, Virginia, South Carolina, and Florida during the 2021 and 2022 field seasons. Results highlight large variation in M. communis abundance across the 4 states. We showed that 1 m elevated pheromone traps caught the most beetles. The age of the lure prior to deployment had a significant effect on trap catch. The lures that were aged for fewer weeks attracted significantly more beetles, with 0- and 2-wk-old lures capturing the greatest numbers.

Abundance of the Sugarcane Borer (Lepidoptera: Crambidae) and Foraging Ants (Hymenoptera: Formicidae) in Sugarcane Grown on Organic and Mineral Soils in Florida.

A study was conducted in Florida to determine sugarcane borer, Diatraea saccharalis (F.), injury and infestation levels in sugarcane (Saccharum spp. hybrids), D. saccharalis parasitism rates, and ant foraging activity in 32 commercial fields as affected by soil type (shallow organic vs deep organic vs mineral). In 2017 and 2018, each field was sampled four times during the summer for D. saccharalis by inspecting 100 sugarcane stalks and for foraging ants using plastic tubes baited with hot dog at 12 locations. One non-parasitized D. saccharalis larva was collected in 2017 and in 2018 out of 12,100 and 12,600 stalks sampled, respectively. Additional sampling of 50 stalks per field in October showed that 0.6% (2017) and 0.1% (2018) of the sugarcane stalks had bored internodes, and one Cotesia flavipes (Cameron) (Hymenoptera: Braconidae) cocoon mass was observed. Seven ant species foraged in sugarcane fields, including the red imported fire ant, Solenopsis invicta Buren, which was the most abundant ant. Solenopsis invicta was not affected by soil type; however, sugarcane fields on shallow organic soils might represent a more suitable environment. The third most abundant foraging ant, Nylanderia bourbonica (Forel), was more abundant in mineral soil fields than in shallow and deep organic soil fields. Results suggest that D. saccharalis population levels in Florida sugarcane are extremely low under current production conditions regardless of soil type. In addition, the observation of C. flavipes, S. invicta, and six other ant species suggest that biological control contributes to these low D. saccharalis population levels.

Relative Abundance of the Stink Bug (Hemiptera: Pentatomidae) Complex Infesting Rice in the Everglades Agricultural Area of Florida.

Florida's rice stink bug complex comprises three species; Oebalus pugnax (F.), O. insularis (Stal), and O. ypsilongriseus (DeGeer), the latter two of which are invasive and exclusive to Florida within the United States. A series of surveys were conducted in 2017 and 2018 to determine the relative abundance of the three species throughout Florida's rice growing region within the Everglades Agricultural Area, in addition to comparing their seasonality within crop and noncrop habitats. Sampling occurred in commercial rice fields and adjacent transects of graminaceous noncrop hosts using sweep nets. Oebalus pugnax (52.7%) and O. insularis (61.7%) were the most abundant species in 2017 and 2018, respectively. Both species were more prevalent in rice fields compared to transects of noncrop hosts. Oebalus ypsilongriseus remained in low abundance relative to O. pugnax and O. insularis, and did not differ in numbers collected among rice and noncrop hosts. Of the noncrop hosts in transects, Panicum dichotomiflorum (fall panicum) was the most abundant across both years. This study is the first report of Oebalus species feeding on Echinochloa crus-galli (common barnyardgrass) in Florida. This study shows that the invasive O. insularis continues to increase in abundance, and has surpassed O. pugnax in terms of regional populations. These results emphasize the need for additional studies to assess the interactions among O. insularis and other Oebalus species in addition to its feeding behavior in Florida rice.

The Sugarcane Borer (Lepidoptera: Crambidae) Infests Rice at Low Population Levels in Florida.

The sugarcane borer, Diatraea saccharalis (F.), rice stalk borer, Chilo plejadellus Zincken, and Mexican rice borer, Eoreuma loftini (Dyar), are stem borers (Lepidoptera: Crambidae) that infest rice (Oryza sativa L.) in the southern United States. A 2-yr study was conducted to determine stem borer injury, infestation, and parasitism levels in Florida. Thirty commercial rice fields were selected during the 2017 and 2018 growing seasons throughout the rice production region in southern Florida. Sampling for stem borer injury and infestations was conducted in each field between the milk and early maturation stages by observing plants at 10 locations, with three 1-m2 quadrats per location. In addition, monitoring for E. loftini adults was conducted using one pheromone trap adjacent to each field. In 2017, the number of rice tillers exhibiting stem borer injury averaged 0.024 tillers/m2 and infestation levels averaged 0.008 stem borers/m2, with only D. saccharalis being observed. In 2018, injury and infestation levels averaged 0.062 injured tillers/m2 and 0.023 D. saccharalis larvae or pupae/m2, respectively. The solitary parasitoid Alabagrus stigma Brullé (Hymenoptera: Braconidae) parasitized 33 and 40% of the collected D. saccharalis in 2017 and 2018, respectively. In addition, pheromone traps did not capture E. loftini adults. This study shows that D. saccharalis infests rice in Florida but at relatively low levels not threatening production and that rice fields are habitats for D. saccharalis parasitoids. This study also suggests that C. plejadellus and E. loftini do not occur in southern Florida.

Differential Probing Behavior of Blissus insularis (Hemiptera: Blissidae) on Resistant and Susceptible St. Augustinegrasses.

Southern chinch bug, Blissus insularis Barber, is a severe pest of St. Augustinegrass throughout the southern United States. Host plant resistance is an environmentally friendly method to manage chinch bug infestations and is increasingly important, as the southern chinch bug develops resistance to insecticides. In this study, in an effort to understand resistance mechanisms in two varieties of St. Augustinegrass ('FX-10' and 'NUF-76'), we used the electrical penetration graph method to quantify stylet probing behaviors in two resistant and two susceptible St. Augustinegrass varieties. Overall, chinch bugs spent less time probing on resistant FX-10 and NUF-76 than on susceptible 'Floratam' and 'Palmetto', and individual probes were shorter in average duration but more numerous in resistant varieties than in susceptible varieties. During probing, chinch bugs spent more time in pathway-associated stylet activities (i.e., penetration through epidermal and mesophyll tissue) in the resistant varieties than in the susceptible varieties, likely indicating difficulty in finding and accessing an ingestion site. As a consequence, chinch bugs spent proportionately much less time engaged in xylem ingestion in both resistant varieties than in susceptible varieties but only in FX-10 were phloem-associated activities significantly reduced compared with those in susceptible varieties. We conclude that there is evidence for non-phloem-associated chinch-bug resistance factors in both NUF-76 and FX-10, and phloem-associated factors in FX-10.

Effects of Elasmopalpus lignosellus (Lepidoptera: Pyralidae) damage on sugarcane yield.

Feeding by lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae), larvae on sugarcane (a complex hybrid of Saccharum spp.) causes leaf damage, dead hearts, and dead plants that can result in stand and yield loss. A 2-yr greenhouse experiment was conducted to examine sugarcane variety and plant age-specific feeding responses to E. lignosellus. Plants growing from single-eye setts of three varieties were exposed to a single generation of E. lignosellus larvae beginning at the three-, five-, and seven-leaf stages. Results indicated that the physical damage and resulting yield loss of plants attacked by E. lignosellus larvae were dependent on the variety and leaf stage at which they were infested. Significantly more plant damage was observed in all three varieties when infested at the three- than at the seven-leaf stage. Larvae caused significantly more plant damage and reduced yield in CP 89-2143 than in CP 78-1628. Tiller production increased in CP78-1628 and CP 88-1762 when infested at the three-leaf stage, whereas tiller production, biomass and sugar yield decreased in CP 89-2143 when infested at all leaf stages, compared with the untreated control. There was no reduction in yield when CP 78-1628 was infested at the three- or five-leaf stages. Biomass was reduced in CP 88-1762 when plants were infested at any of the leaf stages, but sugar yield was reduced only when infested at the seven-leaf stage. These results indicate that compensation in response to E. lignosellus damage was variety dependent and declined with the delay in infestation time.

Effects of harvest residue and tillage on lesser cornstalk borer (Lepidoptera: Pyralidae) damage to sugarcane.

Lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) is an important pest of sugarcane (a complex hybrid of Saccharum spp.) in southern Florida. Cultural controls for E. lignosellus were evaluated in preparation for the potential loss of effective insecticides. Field studies conducted in 2006 compared the effects of harvest residues from green-harvested sugarcane (no preharvest burning to remove leaf matter) on E. lignosellus stalk damage and yield. Damage by E. lignosellus was significantly lower in plant cane plots that were covered with harvest residues collected from a green-harvested field before shoot emergence compared with plots without harvest residue. There were no yield differences between plots with and without harvest residues in plant or ratoon sugarcane fields in the 2006 study. The effects of three postharvest tillage levels (conventional, intermediate, and no tillage) were evaluated in preharvest burned and green-harvested fields in 2008 and 2009. Significantly less E. lignosellus damage was observed in the green- versus preharvest burned fields in both years. Intermediate and no-tillage plots had very little damage in green-harvested field. Conventional tillage plots had the greatest damage in the green-harvested field and the lowest damage in the preharvest burned field. In 2008, biomass yield was greater in the intermediate than conventional tillage in the green-harvested field, but it was greater in the conventional than in other tillage levels in the preharvest burned field. These studies demonstrated that cultural controls could greatly reduce E. lignosellus damage in sugarcane without the use of insecticides.

Temperature-dependent development of Elasmopalpus lignosellus (Lepidoptera: Pyralidae) on sugarcane under laboratory conditions.

Lesser cornstalk borer, Elasmopalpus lignosellus Zeller (Lepidoptera: Pyralidae), is an important sugarcane pest in southern Florida. Development of immature stages (eggs, larvae, prepupae, and pupae) of lesser cornstalk borer was observed on sugarcane at constant temperatures (13, 15, 18, 21, 24, 27, 30, 33, and 36 degrees C), 65-70% RH, and a photoperiod of 14:10 (L:D) h. Total development (from egg deposition to adult emergence) ranged from 22.8 +/- 0.3 d at 33 degrees C to 120.7 +/- 2.8 d at 13 degrees C. Lesser cornstalk borer required 543.48 DD to complete development. Developmental time decreased with increase in temperature from 13 to 33 degrees C and increased markedly at 36 degrees C in all immature stages. One linear and six nonlinear models used to model insect development (Briere-1, Briere-2, Logan-6, Lactin, Taylor, and polynomial models) were tested to describe the relationship between temperature and developmental rate (d(-1)). Criteria used to select the best model were the greatest r (2), lowest residual sum of squares (RSS), and Akaike information criterion values. The Briere-1 model fit the data best and provided the best estimates of developmental temperature thresholds for all immature stages on sugarcane. The estimated lower and upper developmental thresholds for total development were 9.3 +/- 1.8 and 37.9 +/- 0.7 degrees C, respectively. The optimal temperature estimated for the total development was 31.39 +/- 0.9 degrees C. Based on these results, we can forecast the different stages of lesser cornstalk borer at different times in sugarcane. This will enable us to choose the best time to control this pest with greater precision.

Life table studies of Elasmopalpus lignosellus (Lepidoptera: Pyralidae) on sugarcane.

The lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) is an important pest of sugarcane (a complex hybrid of Saccharum spp.) in southern Florida. Reproductive and life table parameters for E. lignosellus were examined at nine constant temperatures from 13 to 36 °C with sugarcane as the larval food source. The pre- and postoviposition periods decreased with increasing temperatures and reached their minimums at 33 and 36 °C, respectively. The oviposition period was longest at 27 °C. The mean fecundity, stage-specific survival, stage-specific fecundity, intrinsic rate of increase, and finite rate of increase were greatest at 30 °C and decreased with increasing or decreasing temperature. The net reproductive rate was greatest at 27 °C. The Logan-6 model best described the relationship between temperature and intrinsic rate of increase. The generation and population doubling times were longest at 13 and shortest at 33 and 30 °C, respectively. The most favorable temperatures for E. lignosellus population growth were between 27 and 33°C. Life table parameters for E. lignosellus reared on sugarcane were greater than for the Mexican rice borer [Eoreuma loftini (Dyar) (Lepidoptera: Crambidae)] reared on an artificial diet at 30 °C. The intrinsic rates of increase for the sugarcane borer [Diatraea saccharalis (F.) (Lepidoptera: Crambidae)] reared on sugarcane or corn were the same as for E. lignosellus reared on sugarcane at 27 °C, but the net reproductive rate was four times higher for the former than the latter borer species.

Oxidative responses of St. Augustinegrasses to feeding of southern chinch bug, Blissus insularis Barber.

Southern chinch bug, Blissus insularis Barber (Hemiptera: Blissidae), is a serious insect pest of St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze, a turfgrass commonly grown in the southeastern United States. Resistance to southern chinch bug has been identified in the polyploid St. Augustinegrass varieties 'Floratam' and 'FX-10', and the diploid 'Captiva'. However, southern chinch bug in Florida and elsewhere has overcome Floratam's resistance. This research investigated the potential role of selected plant oxidative enzymes in resistance/susceptibility to southern chinch bug in two polyploid varieties (FX-10 and Floratam) and two diploid varieties (Captiva and Palmetto). Oxidative enzyme activity was estimated spectrophotometrically from plant samples collected 1, 3, 5, and 8 days after southern chinch bug infestation and from uninfested control plants. Resistant FX-10 and Captiva had significantly higher peroxidase activity, while Captiva had significantly higher polyphenol oxidase activity 5 and 8 days after infestation compared to uninfested controls. FX-10 had higher lipoxygenase activity 3, 5, and 8 days after infestation compared to uninfested controls. Catalase activities did not differ between infested and control plants in any of the varieties tested. Native gels stained for peroxidase indicated that certain isozymes in FX-10 and Captiva were induced 5 and 8 days after infestation. Isozyme profiles of polyphenol oxidase and lipoxygenase did not differ between control and infested FX-10, Floratam, Captiva, and Palmetto. Potential mechanisms to explain the correlation of resistance to southern chinch bug in FX-10 and Captiva with higher activities of oxidative enzymes are discussed.

Role of leaf sheath lignification and anatomy in resistance against southern chinch bug (Hemiptera: Blissidae) in St. Augustinegrass.

Southern chinch bug, Blissus insularis Barber (Hemiptera: Blissidae), is the most serious insect pest of St. Augustinegrass Stenotaphrum secundatum (Walter) Kuntze, a common lawngrass grown in southeastern U.S. states. Host plant resistance to southern chinch bug has been identified in the polyploid St. Augustinegrass 'FX-10' and the diploid 'Captiva'. The objective of this research was to identify possible physical mechanism(s) explaining chinch bug resistance in these cultivars. We studied the distribution of chinch bug salivary sheaths in the preferred tissue for feeding (the axillary shoot) of the two resistant cultivars and two susceptible cultivars, paired for ploidy ('Floratam', polyploid, and Palmetto, diploid). We also investigated the potential role of axillary shoot lignification and anatomy in chinch bug resistance. Salivary sheaths were more abundant on the outermost leaf sheath of axillary shoots of resistant cultivars compared with susceptible cultivars. In contrast, fewer salivary sheaths reached the innermost meristematic tissue in the axillary shoots of resistant St. Augustinegrass cultivars than in the two susceptible cultivars. The polyploid cultivars FX-10 and Floratam had higher total lignin in axillary shoots compared with the diploid cultivars Captiva and Palmetto. However, total lignin content was not correlated with resistance to southern chinch bug. Light microscopic studies found no differences in epidermal layer thickness among resistant and susceptible St. Augustinegrass cultivars. However, transmission electron microscopic studies revealed that the cell walls of the sclerenchyma cells around the vascular bundle of southern chinch bug-resistant FX-10 and Captiva were significantly thicker than the cell walls in susceptible Floratam and Palmetto. Our research suggests that the thick-walled sclerenchyma cells around the vascular bundle play a role in southern chinch bug resistance in St. Augustinegrass, possibly by reducing stylet penetration to the vascular tissue.

Arsenic hyperaccumulation in the Chinese brake fern (Pteris vittata) deters grasshopper (Schistocerca americana) herbivory.

Brake fern, Pteris vittata, not only tolerates arsenic but also hyperaccumulates it in the frond. The hypothesis that arsenic hyperaccumulation in this fern could function as a defense against insect herbivory was tested. Fronds from control and arsenic-treated ferns were presented to nymphs of the grasshopper Schistocerca americana. Feeding damage was recorded by visual observation and quantification of the fresh weight of frond left uneaten and number of fecal pellets produced over a 2-d period. Grasshopper weight was determined before and after 5 d of feeding. Grasshoppers consumed significantly greater amounts of the frond tissue, produced more fecal pellets and had increased body weight on control plants compared with grasshoppers fed arsenic-treated ferns. Very little or none of the arsenic-treated ferns were consumed indicating feeding deterrence. In a feeding deterrent experiment with lettuce, sodium arsenite at 1.0 mm deterred grasshoppers from feeding whereas 0.1 mm did not. In a choice experiment, grasshoppers preferred to feed on lettuce dipped in water compared with lettuce dipped in 1.0 mm sodium arsenite. Our results show that arsenic hyperaccumulation in brake fern is an elemental defense against grasshopper herbivory.