James W. Todd

MALE‐MEDIATED AGGREGATION OF MALE, FEMALE AND 5TH‐INSTAR SOUTHERN GREEN STINK BUGS1 AND CONCOMITANT ATTRACTION OF A TACHINID PARASITE, TRICHOPODA PENNIPES2

In 124 days of field tests, 88.7% of male, 87.3% of female, and 90.2% of 5th‐instar Nezara viridula were caught on cages containing male N. viridula rather than on female or control cages. Likewise, 92% of the female and 86% of the male parasite, Trichopoda pennipes (F.), were caught on cages containing male N. viridula. Attraction of N. viridula occurs throughout the daylight hours, but is strongest in a 5‐min period immediately prior to complete darkness. The data suggest the presence of a male‐emitted aggregation pheromone in N. viridula, acting concomitantly as a kairomone for T. pennipes females.

TEMPORAL AND NUMERICAL PATTERNS OF REPRODUCTIVE BEHAVIOR IN THE SOUTHERN GREEN STINK BUG, NEZARA VIRIDULA (HEMIPTERA: PENTATOMIDAE)

Through hourly observations of 370 individuals in two 11‐day test periods, the temporal and numerical patterns of mating and oviposition behavior in Nezara viridula (L.) were investigated in the laboratory. There was large variation in copulatory durations (1–165 hr), number of copulations per individual (1–9), and time in copulo prior to oviposition (1–176 hr). Number of copulations and mean copulatory duration were negatively correlated for both sexes. Number of copulations was positively correlated with percent of total test time spent mating. Neither males nor females exhibited definitive refractory periods. Oviposition followed a marked diel periodicity.

Nectaried and nectariless cotton cultivars as nectar sources for the adult soybean looper

Moths of the soybean looper (SBL), Pseudoplusia includens (Walker), were released into 1.8 × 3.7 m field cages (10 male:female moth pairs/cage) containing nectaried (floral and extrafloral nectarie...

Kairomones and their use for management of entomophagous insects: VII. The involvement of various stimuli in the differential response ofTrichogramma pretiosum riley to two suitable hosts

The response ofTrichogramma pretiosum Riley to stimuli fromHeliothis zea (Boddie) and fromTrichoplusia ni (Hübner) was examined in the laboratory. Kairomones were responsible, at least in part, for the greater response to naturally depositedH. zea eggs.

Dynamics of spring tobacco thrips (Thysanoptera: Thripidae) populations: Implications for tomato spotted wilt virus management

Abstract The purpose of this study was to monitor tobacco thrips populations during the early spring in Georgia and to determine the role of brachypterous tobacco thrips in epidemics of tomato spotted wilt virus (TSWV). Potted peanuts were placed into fields at four locations in south Georgia throughout the spring of 2000 and 2001. During March 2001, half of all potted peanuts were covered with exclusion/inclusion cages. Tobacco thrips were collected from terminals and flowers on a weekly basis and were identified as macropterous or brachypterous. Nonstructural protein enzyme-linked immunosorbent assay (ELISA) was performed on individual thrips to determine the proportion of brachypterous and macropterous viruliferous thrips in the population. Macropterous thrips were more abundant than brachypterous thrips, except at the Coffee County location during late February and early March. Peaks in thrips abundance and percentage of viruliferous thrips shifted approximately 2 wk later for 2001 than for 2000 at the Tift County location. In laboratory transmission experiments, no difference was found in the ability to transmit TSWV for the two wing morphs. Macropterous thrips appear to be more capable of colonizing and subsequently transmitting TSWV to newly emerged crops. Therefore, it appears that brachypterous tobacco thrips may help to perpetuate the disease cycle of TSWV by harboring the virus over the winter, and by keeping inoculum in the population until temperatures rise and the percentage of macropterous thrips in the population increases.

A regression approach for comparing field resistance of peanut cultivars to tomato spotted wilt tospovirus

Relationships between one TSWV susceptible peanut cultivar (Georgia Runner), one moderately resistant peanut cultivar (C-99R), and the current standard cultivar (Georgia Green) in the southeastern United States were examined. Both moderately resistant cultivars had greater field resistance and higher yields than the susceptible cultivar, Georgia Runner, regardless of the level of disease pressure. Linear regression revealed that under heavy disease pressure, C-99R appears to exhibit greater disease resistance than has been previously reported for Georgia Green and other currently available cultivars. Only 13% and 33% of the variation in yield difference between cultivars could be explained by differences in TSWV incidence for C-99R and Georgia Runner, respectively, when compared by linear regression with Georgia Green. Although the correlations were weak for these relationships, the relationships were still significant (P<0.05). Linear regression equations allow us to designate TSWV risk assesment index scores for cultivars relative to scores for the standard Georgia Green. Such a comparison allows for an examination of the relative levels of resistance observed among cultivars under varying levels of disease pressure. This type of analysis would be most useful under heavy disease pressure situations, when the predictive power of this analysis is greater and differences in field resistance between cultivars would be most significant.

LONGEVITY AND REPRODUCTION OF THE SOUTHERN GREEN STINK BUG, NEZARA VIRIDULA, AS AFFECTED BY PARASITIZATION BY TRICHOPODA PENNIPES

A comparative study of 618 field‐collected Nezara viridula (L.) (Hemiptera: Pentatomidae) snowed that parasitization by Trichopoda pennipes (F.) (Diptera: Tachinidae) caused a 49% reduction in the longevity of male and female N. viridula. Egg fertility and egg‐mass size were not reduced by parasitization. Fecundity of parasitized females was not reduced relative to that of unparasitized females during a time period equal to the lifetime of parasitized females. However, lifetime fecundity of unparasitized females was 3.8 times the lifetime fecundity of parasitized females. Since N. viridula mate and oviposit throughout their lives, parasitization by T. pennipes can cause significant reductions in population levels of this pest.

COMPARISON OF SOYBEAN LOOPER (LEPIDOPTERA: NOCTUIDAE) POPULATIONS IN SOYBEAN AND COTTON/SOYBEAN AGROECOSYSTEMS

During 3 years, soybean fields in southern Georgia were sampled for larval soybean looper (SBL), Pseudoplusia includens Walker. Soybean fields were sampled from 2 area types: areas in which cotton ...

Parasitoids and pathogens of the soybean looper, Pseudoplusia includens (Walker), in South Georgia soybean.

Larvae of the soybean looper (SBL), Pseudoplusia includens (Walker), were collected from soybean fields in south Georgia during the 1982, 1983, and 1984 growing seasons. Larvae were reared in the laboratory to determine levels of parasitism and disease incidence. Twelve parasitoid species including one hyperparasitoid were reared from SBL larvae. The three most common parasitoid species were Copidosoma truncatellum (Dalman), Meteorus autographae Muesebeck, and Cotesia marginiventris (Cresson). The most abundant pathogen was the fungus Entomophthora gammae Weiser, but the fungus Nomuraea rileyi (Farlow) Samson and a nuclear polyhedrosis virus also were present. Peak SBL densities were 73.5 larvae per rowmeter in 1982, 30.9 in 1983, and 19.8 in 1984. Total mortality of larvae collected from different locales due to parasitism and disease ranged from 36.5 to 77.6% during 1982, from 4.8 to 73.2% during 1983, and from 0 to 93.9% during 1984.

The impact of toxaphene applied as a post-emergence herbicide for control of sicklepod, Cassia obtusifolia L., on arthropods associated with soybean

Abstract The impact on arthropod populations of toxaphene (camphechlor) used as a herbicide was compared with cultivation and pre-emergence herbicide usage for control of sicklepod, Cassia obtusifolia L., in soybean. Soybean yields and weed control were also evaluated. Pest resurgence due to toxaphene was found to be limited, but significantly more soybean plants had main stems girdled due to the threecornered alfalfa hopper, Spissistilus festinus (Say), than those plants where toxaphene had not been applied. Both toxaphene usage and cultivation reduced early season predator abundance significantly compared with soybean where weeds were not controlled. However, the greater abundance of predators in soybeans with weeds appeared to be attributable to the increase in habitat diversity provided by the weeds and soybeans and not to a reduction in predator numbers caused by toxaphene in the treated plots. Neither soybean yields, nor the degree of sicklepod control, differed significantly between toxaphene usage and cultivation. Permethrin usage significantly reduced both pest and predator abundance in soybean.