Arthropods were collected from flowering dogwoods infected with Discula destructiva Redlin, causal agent of dogwood anthracnose, to evaluate their ability to transport viable conidia. During 1994, 7.2% of all arthropods collected (n = 375) from diseased trees at three sites in the Great Smoky Mountains National Park were carrying viable conidia of D. destructiva. Most [92.6% (25/27)] of the conidia-infested arthropods were collected during June when sporulation and spread of dogwood anthracnose were increasing. From July through September, the expansion of disease severity and incidence of sporulation diminished and the frequency of conidia-infested arthropods decreased. Several species of arthropods with viable conidia of D. destructiva were collected lending support to the hypothesis that insects and other arthropods may play a role in the spread of dogwood anthracnose.

The Nantucket pine tip moth, Rhyacionia frustrana (Comstock) (Lepidoptera: Tortricidae), is a common pest of Christmas tree and commercial pine plantations in the eastern United States (Yates et al. 1981). During the mid-1980's, a spray timing model for contact insecticides was developed to predict optimal spray dates for controlling R. frustrana in the southeastern Coastal Plain (Gargiullo et al. 1985). Although the model provided for generally acceptable control, analysis of the original degree-day predictions revealed that some errors occur in degree-day accumulation values used to predict insecticide spray dates. We report here the corrected values for both within-generation and cumulative year-long spray date predictions to control R. frustrana in locations where four generations occur annually in the southeastern United States. A similar model for the Piedmont region of Georgia where three generations occur annually accurately predicts spray dates in its current version (Gargiullo et al. 1983).

Fractions obtained by open-column flash chromatography of a crude methanolic extract of the rind of a bitter mutant of Hawkesbury watermelon, Citrullus vulgaris Schrad, were further purified by preparative high-performance liquid chromatography (HPLC) to isolate chemical component(s) that elicit a visitation/feeding stimulancy response to the southern corn rootworm, Diabrotica undecimpunctata howardi Barber. Activity of chromatographic fractions were followed with a laboratory bioassay involving total insect-response counts. The chemical structure of the most active component in C. vulgaris was confirmed by chemical ionization mass spectrometry and proton nuclear magnetic resonance spectroscopy to be cucurbitacin-E glycoside. Two other cucurbitacin-like compounds were isolated and structures for them postulated. A procedure to prepare a crude, biologically active, extract of C. vulgaris is reported. Dose-response data for the crude extract in laboratory tests against two diabroticite beetles D. undecimpunctata howardi and D. virgifera virgifera LeConte are also reported.

Laboratory and field-cage experiments evaluated the efficacy of a water-soluble bait for control of adult diabroticites. The bait was composed of a water-soluble feeding stimulant derived from a bitter mutant of Hawkesbury watermelon (Citrullus vulgaris Schrad), a dye toxin (phloxine B: D & C Red Dye No. 28), and a modified food starch (Mira Sperse 626). In the laboratory, southern corn rootworm, Diabrotica undecimpunctata howardi Barber adults, were exposed to separate bait components and combinations thereof. Eighty percent of adults exposed to the complete bait formulation died within 24 h. Adult mortality increased with higher concentrations of dye and increasing light intensity. Incorporation of the feeding stimulant with the dye reduced the lethal time. The complete bait was most active in sunlight, killing 90% adults in 1 h. Under fluorescent lights, the LT90 for the adults was 48 h. In field cages, using corn plants treated with the bait formulation, numbers of live western corn rootworm, D. virgifera virgifera LeConte, adults were reduced by 80% compared with the untreated control. This new water soluble toxic bait appears suitable for testing on a larger scale in the field as a component of an IPM program for corn rootworm pests.

Diet incorporation and spray chamber assays compared the activity of three commercial formulations of Bacillus thuringiensis Berliner against Heliothis virescens (F.), Helicoverpa zea (Boddie), Pseudoplusia includens (Walker), and Spodoptera exigua (Hübner). The commercial products evaluated were Condor OF® (Ecogen Inc., Langhorne, PA), Dipel ES® (Abbott Laboratories, North Chicago, IL), and Javelin WG® (Sandoz Crop Protection Corp., Des Plaines, IL). Variation in results of the diet incorporation studies illustrated the importance of including a standard reference formulation in the design of the studies and suggested that some standardization of insect strains used in such assays may be important also. Overall results of the diet incorporation studies were similar to those obtained in the spray chamber studies where insects were assayed on sprayed cotton and soybean. Dose-mortality regressions were developed for each B. thuringiensis formulation applied against each insect species on cotton and soybean over a 28-day observation period. These regressions may be helpful in the development of recommendations for the use of B. thuringiensis on cotton and soybean. They may also have value in establishing base-line levels of susceptibility for future resistance monitoring efforts. Median lethal concentrations (LC50s) tended to be slightly higher on cotton than on soybean. The most susceptible insect species was H. virescens, and the least susceptible was S. exigua. LC50s for H. zea and P. includens were similar and intermediate between those of H. virescens and S. exigua. Javelin WG tended to exhibit the highest activity per unit weight of commercial product, but the relative differences among the commercial formulations were influenced by insect species.

The effects of irrigation and soybean maturity group (Group V ‘Forrest’ variety vs Group VII ‘Braxton’ variety) on the seasonal abundance of arthropod pest and beneficial population densities were examined in large-plot field tests at the Attapulgus Research Center in Attapulgus, GA, in 1987 through 1990. In general, soybean plant growth was more abundant, yields were higher, and canopy closure indices were lower in irrigated than in non-irrigated plots for both varieties. Irrigation and the resultant increased soybean vegetation supported a greater overall seasonal abundance of all five of the insect pests monitored: stink bugs, primarily Nezara viridula (L.), velvetbean caterpillars, Anticarsia gemmatalis Hübner, soybean loopers, Pseudoplusia includens (Walker), threecornered alfalfa hoppers, Spississtilus festinus (Say), and green cloverworms, Plathypena scabra (F.). No overall varietal effects were noted for N. viridula; however, each year, population densities were higher in the early-maturing ‘Forrest’ up to julian day 250 then densities were higher in the later-maturing ‘Braxton’ for the remainder of the grown season. Mean estimates of the seasonal abundance of A. gemmatalis and P. scabra populations were similar between the two varieties; however, P. includens and S. festinus were more abundant on Forrest than on Braxton. Total arthropod predators, including Nabis spp., Geocoris spp., and spiders, also were more abundant on irrigated soybeans, while overall varietal means were similar. Yearly analyses revealed significant irrigation and variety effects for most of the species sampled.

We examined the effect of varying thresholds for treatment of first generation European corn borer, Ostrinia nubilalis (Hübner), infestations in early-season fresh market sweet corn in eastern New York over a 3-year period. Seven treatment thresholds were compared: (1) 15% infested plants at whorl stage, 5% infested plants at tassel and silk stage, (2) 15% at whorl stage, 15% at tassel and silk stage, (3) 30% at whorl stage, 5% at tassel and silk stage, (4) 30% at whorl stage, 15% at tassel and silk, (5) 5% at tassel and silk stage, (6) 15% at tassel and silk stage, and (7) control (untreated). When thresholds were reached, permethrin was applied using an air-blast sprayer. Results indicated little difference in percentage marketable ears whether plants were treated or not at whorl stage, and the tassel stage threshold could be raised to 15% infested plants with no significant effect on percentage marketable ears. We found no difference in marketable yield among plots treated from one side or both sides with an air-blast sprayer.

Experiments were conducted using tritiated European corn borer, Ostrinia nubilalis (Hübner), pheromone, (Z)-[11,12-³H₂]-11-tetradecen-1-ol acetate, a tritiated fluorinated analog of the European corn borer pheromone, 2-fluoro-(Z)-[11,12-³H₂]-11-tetradecen-1-ol acetate, and methyl-4-bromocrotonate (MBC) to determine if pheromone catabolism proceeds on the moth's antennae via the β-oxidation pathway of fatty acid degradation. When antennae were treated with tritiated natural pheromone plus MBC (a precursor of the known β-oxidation inhibitor, 4-bromocrotonic acid), catabolism of the pheromone was significantly inhibited. When the 2-fluoro pheromone analog was applied alone to antennae, it was hydrolyzed to the corresponding alcohol but was not degraded. MBC had no effect on catabolism of the 2-fluoro analog, and 2-fluoro substitution inhibited entrance of the compound into β-oxidation. These results demonstrate that β-oxidation is the primary oxidative pathway by which pheromone is degraded on the antennae of European corn borer moths.

During 1992–1993, nine insecticides and eight mixtures of these insecticides at a 1:1 ratio were tested for their toxicity to adults of the B-strain whitefly, Bemisia tabaci (Gennadius), collected from cotton plants in a greenhouse in the Lower Rio Grande Valley of Texas. Synergistic, additive, or antagonistic properties of the mixtures were determined in a glass vial bio-assay. Endosulfan+bifenthrin was the most toxic mixture tested and was synergistic with a median lethal concentration (LC50) that was significantly less than the LC50s of either insecticide tested alone. Acephate+bifenthrin and amitraz+bifenthrin provided additive toxicity while amitraz+buprofezin and endosulfan+methyl parathion were antagonistic in their effect on adult whiteflies.

Median lethal concentration (LC50) values of bifenthrin and endosulfan were determined for dead and moribund + dead categories for adults of the silverleaf whitefly, Bemisia argentifolii (Bellows and Perring) (formerly sweetpotato whitefly, B. tabaci (Gennadius), strain B), in 3-h vial bioassays in Florida, Georgia, and Texas in 1991 and 1992. For the moribund + dead category in Florida, LC50 values for bifenthrin ranged from 0.00076 to 1.48 μg/vial, a 1,947-fold difference. An LC50 as high as 128.1 μg bifenthrin/vial for adults from cabbage in Texas was determined for the dead category. For endosulfan in Florida, LC50 values of the moribund plus dead categories for endosulfan ranged from 0.04 to 35.6 μg/vial, an 890-fold difference. An LC50 as high as 119.7 μg endosulfan/vial was determined for adults from cotton in Texas for the dead category. The wide ranges of LC50 values for both insecticides suggest the presence of resistant and susceptible whiteflies in all three states.