Ron Cherry

SURVEY TRAPS FOR PARASITOIDS, AND COCCINELLID PREDATORS OF THE CITRUS BLACKFLY, ALEUROCANTHUS WOGLUMI1

The attractiveness of sticky traps of eight colors for two parasitoids Amitus hesperidum Silvestri and Prospaltella opulenta Silvestri, and seven species of coccinellid predators of the citrus blackfly, Aleurocanthus woglumi Ashby (Homoptera: Aleyrodidae) was evaluated in insectory and field tests.

Role of Leaf Sheath Lignification and Anatomy in Resistance Against Southern Chinch Bug (Hemiptera: Blissidae) in St. Augustinegrass

ABSTRACT 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.

Temperature-Dependent Development of Elasmopalpus lignosellus (Lepidoptera: Pyralidae) on Sugarcane Under Laboratory Conditions

ABSTRACT 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°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°C to 120.7 ± 2.8 d at 13°C. Lesser cornstalk borer required 543.48 DD to complete development. Developmental time decreased with increase in temperature from 13 to 33°C and increased markedly at 36°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 r2, 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°C, respectively. The optimal temperature estimated for the total development was 31.39 ± 0.9°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.

Resistance to Two Classes of Insecticides in Southern Chinch Bugs (Hemiptera: Lygaeidae)

Abstract Southern chinch bugs were tested from 10 locations in Florida to determine possible resistance to 4 insecticides. Resistance of varying degrees was found in all 4 insecticides: bifenthrin, deltamethrin, imidacloprid, and lambda-cyhalothrin. This study is the first to show southern chinch bug resistance to the latter 3 insecticides. Our data also show that multiple locations are necessary for insecticidal testing for southern chinch bugs since results from 1 location can be very misleading.

Abundance and Spatial Distribution of Wireworms (Coleoptera: Elateridae) in Florida Sugarcane Fields on Muck Versus Sandy Soils

Abstract Wireworms are important insect pests of Florida sugarcane. Our objective was to determine the abundance and spatial distribution of wireworms in Florida sugarcane on muck versus sandy soils. Fourteen commercial sugarcane fields were sampled for wireworms on farms in southern Florida. Melanotus communis (Gyllenhal) was the most abundant wireworm found in both soil types. Other less abundant wireworms found and discussed are Conoderus spp., Ischiodontus sp., and Glyphonyx bimarginatus Schaeffer. There were no significant differences in densities of G. bimarginatus, M. communis, or total wireworms of all species in muck versus sand fields. Significantly more Conoderus spp. were found in sandy fields and significantly more Ischiodontus sp. were found in muck fields. The spatial distribution of the wireworms within fields was similar in both soil types. In muck, wireworms in 4 fields were randomly distributed, aggregated in 3 fields, and uniformly distributed in no fields. In sand, wireworms in 3 fields were randomly distributed, aggregated in 4 fields and uniformly distributed in no fields.

REPELLENCY OF THE BIOPESTICIDE, AZADIRACHTIN, TO WIREWORMS (COLEOPTERA: ELATERIDAE)

ABSTRACT The neem tree Azadirachta indica A. Juss produces numerous allelochemical compounds. The most effective active ingredient in A. indica based insecticides is azadirachtin. We found that azadirachtin did not cause mortality, antifeeding responses, or change growth rate of Melanotus communis (Gyllenhal) wireworms. However, azadirachtin treated soil was repellent to the wireworms. This is the first report of azadirachtin being repellent to any of the large and economically important family of Elateridae.

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

ABSTRACT 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 insuhris Barber, feeding on St. Augustinegrass, and western chinch bug, Blissus occiduus Barber, feeding on buffalograss. This is only the third time a heteropteran 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 1010 &OHgr;, plus 1013 &OHgr;, 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 &KHgr; 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 107 &OHgr;, with either DC or AC applied voltage, is optimal to detect all resistanceand 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.

SEASONAL POPULATION DYNAMICS OF WIREWORMS (COLEOPTERA: ELATERIDAE) IN FLORIDA SUGARCANE FIELDS

Abstract Wireworms are important insect pests of Florida sugarcane. The objective of this study was to determine the seasonal population dynamics of wireworms in Florida sugarcane. In a preliminary test, significantly more total numbers of wireworms were found under sugarcane stools than between stools in a row or between rows. Hence, the sugarcane stool was used as the sampling site for wireworms in the population dynamics study. A sugarcane field was sampled for wireworms monthly from Jun 2004 to Jun 2006. The total number of wireworms was significantly less in the summer than other seasons and these wireworms were also significantly smaller at this time. Data in this study should be useful to southern Florida growers in understanding expected wireworm damage in different seasons.

New Source of Southern Chinch Bug (Hemiptera: Lygaeidae) Resistance in a Diploid Selection of St. Augustinegrass

Over 400,000 ha of St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze, are managed as a turfgrass in the southern United States, and the southern chinch bug, Blissus insularis Barber, is it...

SEASONAL WING POLYMORPHISM IN SOUTHERN CHINCH BUGS (HEMIPTERA: LYGAEIDAE)

St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntze lawns are used throughout the southern United States for their climatic adaptation and their ability to tolerate full sun to moderate shade. The southern chinch bug, Blissus insularis Barber is the plants most damaging pest (Crocker 1993). The adaptability of this insect is shown by its developing resistance to insecticides (Reinert & Portier 1983) and overcoming host plant resistance (Busey & Center 1987; Cherry & Nagata 1997). Southern chinch bugs (SCB) can occur as either macropterous or brachypterous adults. However, other than anecdotal reports, there are little field data on the occurrence of these wing forms in SCB. Also, reasons for the occurrence of brachypterous versus macropterous adults in SCB are poorly understood. Wilson (1929) reported that both macropterous and brachypterous SCB adults occur in Florida and these vary in relative numbers during the year, but no data were given. Komblas (1962) reported that population density was a factor in SCB wing form, noting that a larger percentage of nymphs raised under crowded conditions developed into macropterous adults than did uncrowded nymphs. Leonard (1966) discussed migration as an important factor in SCB wing formation. Lastly, Reinert and Kerr (1973) noted that although macropterous and brachypterous adults may be found in SCB, the latter predominates. However, reasons for the occurrence of the two wing forms were not discussed. The objectives of this study were to determine the seasonal occurrence of wing polymorphism in SCB in southern Florida and to determine if wing polymorphism is correlated with field population density. Chinch bugs were collected from infested St. Augustinegrass lawns in Palm Beach County, Florida from December 1999, to December 2000. Five new SCB infestations were located each month by looking for damaged yellow grass and then visually confirming the presence of SCB. Insects were collected by suctioning for 5 minutes a 1 x 1 m area at each infestation. Nymphs and adults were collected by suction into a gasoline powered modified WeedEater? Barracuda blower/vacuum (Poulan/WeedEater, Shreveport, LA). The use of a suction technique for sampling SCB was described by Crocker (1993). After collection, samples were frozen for later counting in a laboratory. Samples were passed through as U.S.A. Standard Testing Sieve #10 (2 mm opening) to remove large debris. Microscopic examination was used to determine the sex and wing form of each adult and count nymphs. In order to determine possible seasonal differences in wing polymorphism, samples from 3 month periods were pooled. For the purposes of this paper, winter is defined as December, January, and February, spring is March, April, and May, summer is June, July, and August, and fall is September, October, and November. These definitions correspond to seasonal definitions for the North Temperate Zone (Guralnik 1982). Mean differences in population density (nymphs + adults per sample) between seasons were determined using Tukeys test. Mean differences in percentage macropterous adults (macropterous adults/total adults per sample) between seasons were also determined using Tukeys test (SAS 1996). Pearsons correlation (SAS 1996) of percentage macropterous adults versus SCB density (adults, nymphs, or total = adults + nymphs) in all samples (N = 60) was conducted to examine possible relationships between wing form and field population density. Pearsons correlation for percentage macropterous males (macropterous males/ total adults) versus percentage macropterous females in all samples (N = 60) was also conducted to determine if both sexes were responding similarly to the factor or factors causing macroptery in the field. There was no significant difference in population density between the four seasons (Table 1). However, means during the winter-spring were lower than the summer-fall. Hence, data from winter and spring were pooled and compared against pooled data from summer and fall. The summer-fall population density (mean = 1746, SD = 3447) was significantly greater (alpha = 0.05) than winter-spring population density (mean = 431, SD = 682) by t-test analysis (t = 2.1, 58 DF). These data are in general agreement with Komblas (1962) and Reinert and Kerr (1973). Komblas (1962) reported that SCB populations decreased during winter in Louisiana. Reinert and Kerr (1973) also reported that field populations of SCB decrease drastically in cooler weather. There was no significant difference in percentage of macropterous adults between the four seasons (Table 1). However, as with population density, means during the winter-spring were again lower than the summer-fall. Hence, data from the winter and spring were again pooled and compared against pooled data from the summerfall. The summer-fall macroptery (mean = 22.3, SD = 18.1) was significantly greater (alpha = 0.05)