Xing Ping Hu

Seasonal Variation of Critical Thermal Limits and Temperature Tolerance in Formosan and Eastern Subterranean Termites (Isoptera: Rhinotermitidae)

Abstract Critical temperatures and the upper lethal limit (ULL) of field collected workers of Formosan subterranean, Coptotermes formosanus Shiraki, and eastern subterranean termites, Reticulitermes flavipes (Kollar), were measured monthly from September 2001 to August 2002. Monthly mean critical thermal maxima (CTMa), ULL, and critical thermal minimum (CTMin) fluctuated significantly throughout the year. Seasonal variations of CTMax and ULL of both species were slightly, but significantly, statistically correlated with seasonal variation of habitat soil temperatures at 15-cm depth. Regression analyses revealed a significant linear relationship between CTMin and habitat temperatures for both termites as well. The two termite species responded positively to temperature changes in a similar manner. The values of all three parameters were significantly greater for C. formosanus (CTMax: 44.8–45.9°C, ULL: 49.1–50.4°C, CTMin: 7.2–9.0°C) than R. flavipes (CTMax: 43.5–44.9°C, ULL: 46.9–48.3°C, CTMin: 1.0–4.9°C). R. flavipes had a wider range between the upper and lower critical temperatures than C. formosanus. The three thermal tolerance parameters were not correlated with worker body mass. The significance of the critical and lethal temperatures and comparisons with previous studies are discussed.

Attracticidal spheres for controlling apple maggot flies: commercial-orchard trials.

Wooden pesticide‐treated red spheres and biodegradable sugar/flour pesticide‐treated red spheres were compared with wooden sticky‐coated red spheres and insecticide sprays for controlling apple maggot flies, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), in small blocks of apple trees in Massachusetts commercial orchards in 1997, 1998 and 1999. Pesticide‐treated spheres received a coating of 70% latex paint, 20% feeding stimulant (sucrose), and 10% formulated insecticide (containing 20% imidacloprid). To replenish sucrose lost during rainfall, wooden spheres were capped with a disc comprised of hardened sucrose that seeped onto the sphere surface, whereas the surface of sugar/flour spheres received sucrose that seeped from the interior. Each year, each of the 24 perimeter trees of each non‐sprayed block received a sphere baited with butyl hexanoate (an attractive component of host fruit odor), with the intent of intercepting immigrating flies. Based on captures of flies on unbaited sticky‐coated red spheres placed near the center of each block and on periodic samples of fruit for injury, there was a consistent pattern of treatment performance. Each year, sticky‐coated spheres were only slightly less effective than two or three sprays of organophosphate insecticide, sugar/flour pesticide‐treated spheres were only slightly less effective than sticky spheres, and wooden pesticide‐treated spheres were least effective. Versions of pesticide‐treated spheres used in 1999 were more durable than those used in previous years, but further improvement is needed before either wooden or sugar/flour pesticide‐treated spheres can be recommended for grower use.

Toxicity and Residual Effectiveness of Insecticides on Insecticide-Treated Spheres for Controlling Females of Rhagoletis pomonella (Diptera: Tephritidae)

Abstract This study evaluated the toxicity of five technical-grade insecticides of four different classes to apple maggot females, Rhagoletis pomonella (Walsh), following a 10-min exposure period in insecticide-coated glass jars, with or without a feeding stimulant (sucrose) present. According to LC90 values for toxicity by ingestion and tarsal contact, imidacloprid was 1.5 times more toxic than dimethoate or abamectin, diazinon was less toxic, and phloxine B (a phototoxic dye) least toxic. Based on LC90 values for tarsal contact alone, dimethoate was 2.3, 4.0, and 18.4 times more toxic than imidacloprid, abamectin, and diazinon, respectively. Contact alone with phloxine B caused no mortality. When exposure was assessed using spheres coated with a latex paint mixture containing sucrose and formulated dimethoate (Digon 400 EC) or imidacloprid (Provado 1.6 F) at concentrations ranging from 5 to 70 g (AI)/cm2, both insecticides showed reduced effectiveness compared with toxicities from glass jar tests, with Digon two times more toxic than Provado. After exposure to artificial rainfall and retreatment with sucrose, Digon- and Provado-treated spheres exhibited greatest residual effectiveness, with diazinon-treated spheres less effective. Spheres treated with formulated abamectin (Agri-Mek 0.15 EC) at 1.0% (AI) performed only slightly better than phloxine B-treated spheres, which completely lost effectiveness after exposure to rainfall. Spheres treated with formulated imidacloprid (Merit 75 WP) at 1.5% (AI) showed equal or better residual efficacy in killing apple maggot flies (>80% mortality, shorter lethal duration of feeding) over a 12-wk exposure period to outdoor weather than spheres treated with Digon at 1.0% (AI) after both types were retreated with sucrose. Our results indicate that imidacloprid is a promising safe substitute for dimethoate as a fly killing agent on lure-kill spheres. Imidacloprid formulated as Merit 75 WP had greater residual efficacy than imidacloprid formulated as Provado 1.6 F.

Controlled release of sugar and toxicant from a novel device for controlling pest insects

A novel biodegradable device, designed for long-lasting residual effectiveness of feeding stimulant (sugar) and insecticide (dimethoate) against apple maggot files and other insects, was formulated. The device is an 8-cm diameter fruit-mimicking sphere, consisting of 42-50% sugar entrapped in a mixture of gelatinized corn flour and wheat flour in the presence of glycerin, and coated with a layer of latex paint containing dimethoate and sugar. We found that the outer layer of paint prevents cracking of the sphere upon drying and creates a barrier to control the release of both sugar and dimethoate. Releases of each ingredient were screened first by chemical analysis and then by bioassays in the laboratory and in field cages against apple maggot flies. Chemical analysis demonstrated strong potential for controlled release of water-soluble feeding stimulant and water-insoluble insecticide measured as a function of the amount of rainfall and duration of exposure time. Field results showed greater than 70% insecticidal activity after 11 weeks of sphere exposure in an orchard. This device has the potential to be used for a variety of insect-control applications through manipulating its shape, color and texture into forms known to be attractive to target insects, and by employing various toxicants designed to be effective against such insects.

Attraction of mature Ceratitis capitata females to 2-heptanone, a component of coffee fruit odor

In indoor laboratory-cage and outdoor field-cage assays, we evaluated the attraction of released, protein-fed, mature Mediterranean fruit fly females to six volatile compounds emitted by attractive crushed ripe coffee fruit: 3-methyl-1-butanal, decanal, 3-methyl-1-butanol, 2-(Z)-pentenol, 2-(E)-hexenol, and 2-heptanone. Previous tests in a wind tunnel indicated that each of these six compounds was more attractive than clean air to females. In laboratory cage assays, none of the compounds elicited a response significantly greater than that to water. In field-cage assays, 2 or 4 μl of 2-heptanone in 5 ml of water (but none of the other compounds at 2 or 4 μl in 5 ml of water) consistently attracted protein-fed medflies at significant levels that averaged about five times greater than attraction to water alone, although about 40% less than attraction to odor of coffee fruit extract. All types of mature protein-fed females tested (laboratory-cultured virgin, laboratory-cultured mated, wild mated) in field-cage assays responded similarly to 2-heptanone, whereas same-age (9- to 11-day-old) protein-deprived females did not respond significantly to 2-heptanone. Response of protein-fed females to 2-heptanone increased progressively with increasing dose (1, 2, 4, or 8 μl in 5 ml of water). Addition of 2 μl of 2-heptanone or 2 μl of any of the other compounds tested to 5 ml of water extract of coffee fruit did not enhance attractiveness of the extract. Relative to response to water, protein-fed females consistently exhibited a significant positive response to odor of coffee fruit extract but no significant response to odor of Nulure (a proteinaceous food attractant). Together, our findings suggest that mature protein-fed females were responding to 2-heptanone as though it were an oviposition-site stimulus rather than a feeding-site stimulus.

EFFECTS OF SUGAR/FLOUR SPHERES COATED WITH PAINT AND INSECTICIDE ON ALIGHTING FEMALE CERATITIS CAPITATA (DIPTERA: TEPHRITIDAE) FLIES

We studied the behavior and fate of mature, wild-origin Ceratitis capitata (Wiedemann) females allowed to feed on 7-cm-diam spheres comprised of a mixture of sugar, flour and glycerin and coated with yellow latex paint containing either no insecticide, dimethoate (1.5% a.i.) or imidacloprid (1.5% a.i.). Females feeding on imidacloprid-treated spheres for 20 sec exhibited very little tendency to forage within host plants or to lay eggs either shortly after or 24 h after feeding, and suffered high mortality within 48 h. In contrast, females feeding on dimethoate-treated spheres for 180 sec exhibited, shortly thereafter, a tendency to forage within host plants and to lay eggs about equal to that of females feeding on untreated spheres, although they suffered high mortality within 24 h. In a field test, imidacloprid-treated sugar/flour spheres provided a significant level of protection of fruit from oviposition by C. capitata during 24 h periods (equal to that provided by sticky yellow spheres), whereas dimethoate-treated spheres did not. Further research on long-term activity of pesticide residue and on sphere performance under natural conditions will be necessary, however, before sugar/flour spheres coated with yellow latex paint and insecticide can be recommended for control of C. capitata.

Effects of indoxacarb concentration and exposure time on onset of abnormal behaviors, morbundity, and death in eastern subterranean termite (Isoptera: Rhinotermitidae).

ABSTRACT Onset of abnormal behaviors, morbundity, and death was evaluated in eastern subterranean termites, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), exposed to several concentrations (45, 90, 135, and 180 ppm) of indoxacarb and to several (5, 10, 20, 40, 80, and 160 min) exposure periods. Abnormal behaviors, morbundity, and death occurred in a predictable sequence: disorientation, ataxia, and morbundity followed by death. In general, higher concentrations and longer exposure periods resulted in faster onset of abnormal behaviors, morbundity, and death. The average onset time of abnormal behaviors, morbundity, and death was faster for groups of termites compared with individuals exposed to similar concentrations and periods of contact. The importance of onset times of abnormal behaviors as another important measure of the toxicity of slow-acting toxicants is discussed.

Preoverwintering Copulation and Female Ratio Bias: Life History Characteristics Contributing to the Invasiveness and Rapid Spread of Megacopta cribraria (Heteroptera: Plataspidae)

ABSTRACT Prewinter copulation, sperm storage, and oocyte development in overwintering adult Megacopta cribraria (F.) was examined in Alabama (Lee Co.). Microscopic examinations of the spermathecae and ovaries were made in females and of the testes in males that were collected approximately weekly from September 2013 through March 2014. The results indicated that approximately 15% of females mated before entering winter dormancy and sperm was stored in their spermatheca for up to seven months, oocytes in mated overwintering females proceeded to postblastoderm stage before the onset of spring feeding and mating in March, all of the overwintering males had sperm in their testes, and the ratio of females gradually increased in populations during overwintering. This study indicates that both males and females are capable of reproductive dormancy. The biological significance of these life cycle aspects is discussed from the viewpoints of invasiveness and adaptation.

Behavioral Response of Two Subterranean Termites (Isoptera: Rhinotermitidae) to Vibrational Stimuli

Behavioral responses to vibrational stimuli were examined in two subterranean termite species, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar). Termites habituated to vibrational stimulation when in social groups, but failed to do so individually, indicating that habituation is a collective action. In assays on termite groups, both species demonstrated a similar pattern of behavioral responses to vibrational stimuli: evanescent cessation of activity and movement, followed by withdrawal from the vibration source. Groups of both species then gradually moved back toward the vibration source as a consequence of continuous exposure. However, it took a significantly shorter period for C. formosanus to return (57 s) to the test arena and to resume (80 s) normal foraging activities in the test arena compared with R. flavipes, which took 97 and 227 s, respectively, when exposed to the vibration frequency of 120 bmpm. High vibration frequency (240 bmpm) increased the time required to return (C. formosanus, 80 s; R. flavipes, 153 s) and to resume regular locomotion (C. formosanus, 186 s; R. flavipes, 263 s). Our experiments demonstrate that workers play a crucial part in adjusting groups of termites to distressful vibrations. Soldiers of R. flavipes demonstrated similar behavioral responses as workers, however, C. formosanus soldiers exhibited a transient positive response before withdrawal.

Kudzu-deprived First-generation Megacopta cribraria (F.) (Heteroptera: Plataspidae) Are Capable of Developing on Alternative Legume Species1

ABSTRACT  The biology of Megacopta cribraria (F.) (Heteroptera: Plataspidae) is not well understood in its new North American distribution, especially its development on alternative host plant species. We investigated whether overwintered M. cribraria could directly feed and oviposit on other legume species (Fabales: Fabaceae) without feeding on kudzu, Pueraria montana (Loureiro) Merrill var. lobata (Willdenow) Maesen & S. Almeida, and subsequently complete a first-generation on these species in no-choice greenhouse assays. Overwintered M. cribraria successfully oviposited on mung bean, Vigna radiata (L.) R. Wilczek; black-eyed pea, Vigna unguiculata (L.) Walp; lima bean ( = butter bean), Phaseolus lunatus L.; soybean, Glycine max L. Merrill; and kudzu. There were no differences in oviposition or the hatch rates on different legume species, although hatch rate was highest for soybean followed by kudzu, lima bean, mung bean, and black-eyed pea, respectively. First-generation M. cribraria developed on all legume species except black-eyed pea in 55.6 ± 1.6 d with little variation in developmental time of the instars. However, there were significantly more first instars molting to second instars on kudzu (19.6 ± 3.3), soybean (14.7 ± 3.0), and mung bean (19.0 ± 1.0) than on lima bean (5.3 ± 2.4). Mean developmental days of the first, second, and fourth instars were consistent at about seven days, while the third and fifth instars took longer to develop. Mortality from egg to adult was greatest on black-eyed pea, followed by lima bean, kudzu, mung bean, and soybean. These results indicate that overwintered M. cribraria adults are able to bypass kudzu to directly develop on soybean, lima bean, and mung bean crops.