Tomislav Curkovic

Courtship Behavior in Choristoneura rosaceana and Pandemis pyrusana (Lepidoptera: Tortricidae)

Abstract The characterization of courtship behavior in two sympatric and synchronic leafroller species, Choristoneura rosaceana (Harris) and Pandemis pyrusana Kearfott, indicated that only pheromone permeated airflow was needed as a releaser to initiate the male mating sequence. Mating ethograms demonstrate that males of both species perform six observable, discrete, and homogeneous steps: 1) wing fanning; 2) first contact; 3) male next to female (mostly in C. rosaceana), head-to-head (only P. pyrusana); 4) curled abdomen; 5) genitalia engagement; and 6) end-to-end position (mating). The sequences were highly stereotypic, suggesting that once a male starts the mating sequence, the rest of the steps will most likely follow. First contact with the female was a preprogrammed response, not requiring further cues. Copulation was more likely when the female remained stationary after first contact. Unsuccessful mating sequences were frequent during the study because females escaped by walking away, turning around, or jumping away. Because courtship behavior is a mechanism to select sexual partners, it is possible to hypothesize that responses resulting in an unsuccessful mating (assumed to be rejection) validate this mechanism. The mating sequence of C. rosaceana best matches the simple courtship behavior model, whereas the sequence in P. pyrusana resembles an interactive courtship. Overall results indicate that courtship behavior in both species would be compatible with attracticide (i.e., sex pheromone + insecticide) technology that requires direct contact between males and the pheromone source.

Evidence that Cerambycid Beetles Mimic Vespid Wasps in Odor as well as Appearance

We present evidence that cerambycid species that are supposed mimics of vespid wasps also mimic their model’s odor by producing spiroacetals, common constituents of vespid alarm pheromones. Adults of the North American cerambycids Megacyllene caryae (Gahan) and Megacyllene robiniae (Forster) are conspicuously patterned yellow and black, and are believed to be mimics of aculeate Hymenoptera, such as species of Vespula and Polistes. Adult males of M. caryae produce an aggregation-sex pheromone, but both sexes produce a pungent odor when handled, which has been assumed to be a defensive response. Headspace aerations of agitated females of M. caryae contained 16 compounds with mass spectra characteristic of spiroacetals of eight distinct chemical structures, with the dominant compound being (7E,2E)-7-ethyl-2-methyl-1,6-dioxaspiro[4.5]decane. Headspace samples of agitated males of M. caryae contained five of the same components, with the same dominant compound. Females of M. robiniae produced six different spiroacetals, one of which was not produced by M. caryae, (2E,7E)-2-ethyl-7-methyl-1,6-dioxaspiro[4.5]decane, and five that were shared with M. caryae, including the dominant (2E,8E)-2,8-dimethyl-1,7-dioxaspiro[5.5]undecane. The latter compound is the sole spiroacetal produced by both males and females of a South American cerambycid species, Callisphyris apicicornis (Fairmaire & Germain), which is also thought to be a wasp mimic. Preliminary work also identified spiroacetals of similar or identical structure released by vespid wasps that co-occur with the Megacyllene species.

SELECTIVE ATTRACTION OF Vespula germánica (Hymenoptera: Vespidae) TO FEEDING BAITS ENHANCED WITH ISOBUTANOL AND ACETIC ACID

Vespula germanica (F.) has a negative impact on agriculture, beekeeping, and tourism in Chile. Therefore, environmentally-friendly strategies need to be implemented to control this serious pest. The objective of this study was to evaluate the response of adults of V. germanica to different types of baits with acetic acid + isobutanol (AAIB) added. The selected baits were: blood and bone flour (BF), raspberry jam (RJ), and sweet condensed milk (CM). The trial was conducted in a severely infested site in central Chile. Mixtures were placed in bottle traps. All of the traps were monitored daily from Monday to Friday during 5 weeks, and rebaited every week. A randomized complete block design, with 12 treatments and 4 replicates was used. Captures of V. germanica and other social hymenopterans were identified and data were recorded; V. germanica individuals approaching the trap openings (= visits) were also counted. A number of 15,480 V. germanica individuals, which were mostly workers, were captured. The most attractive baits were CM and BF + 2 mL AAIB. Feeding baits attracted significantly more workers with increasing concentrations of chemicals (AAIB), and significantly more wasps than the feeding baits alone. Lesser captures occurred of Apis mellifera workers (1,046), while the preference trend differed from that observed for V. germanica in several treatments. A number of 854 Polistes buyssoni workers were captured, but no differences were found between treatments. In addition, a number of 466 V. germanica visited the traps, but the trend observed with captures only occurred in traps baited with BF + AAIB, whereas no preference trend was observed for mixtures with RJ and CM. The results indicate that these attracting baits can be used not only to massively and selectively capture and destroy adults of V. germanica, but also to develop feeding baits not attractive for A. mellifera.

EFFECT OF AN INSECTICIDE FORMULATION ON Hippodamia convergens (GUÉRIN) AND NYMPHS OF Aphis craccivora (KOCH) IN THE LABORATORY

The toxicity of an insecticide formulation containing triazamate and alpha-cypermethrin (120 and 38.4 g L-1, respectively) was evaluated on Hippodamia convergens (Guérin), and its prey, the aphid Aphis craccivora (Koch). Both insects were collected on alfalfa, Medicago sativa L., and reared on faba bean (Vicia faba L.). The formulation was sprayed on alfalfa leaflets in a Potter tower at the maximum dose recommended (400 mL ha-1) and at 50, 25, 15, 10, 5 and 1% of that dose. The eggs and pupae of H. convergens were left on the leaflets after treatment. The mobile stages of both insects were set on the leaflets once they had dried at room temperature to prevent them from escaping. Mortality during the growth stages of H. convergens and adult aphids was evaluated 24 and 48 h after treatment application. The LC50 for both insects was determined by Probit analysis. The maximum dose was moderately toxic (mortality from 80 to 99%) for adults, pupae, and eggs of H. convergens, but toxic (> 99%) for A. craccivora and the ladybird larvae. The LC50s for adults, eggs, larvae, and pupae of H. convergens were 0.405; 341.2; 0.163; and 1.057 mL L-1, respectively, and 0.013 mL L-1 for A. craccivora. The lowest dose (1% of the maximum) caused 93% aphid mortality, indicating that low doses are sufficient to control this pest by spraying. Therefore, the commercial dose could be reduced to this amount and still control A. craccivora, resulting in lesser effects on H. convergens.

Toxicity of Field-Aged Permethrin-Loaded Attracticides on Choristoneura rosaceana (HARRIS) and Pandemis pyrusana Kearfott (Lepidoptera: Tortricidae) Adult Males and Females

Lethal and sub lethal effects were evaluated in the laboratory on Choristoneura rosaceana (Harris) and Pandemis pyrusana Kearfott males exposed to an attracticide loaded with permethrin and aged in the field. The effect of pairing conspecific females with previously intoxicated males was also evaluated. In both species a significantly greater mortality of male moths (≥ 95%) was observed 24 h after exposure to the attracticide formulation. Likewise, high levels of knock down (≥ 75%) were observed in males of both species 1 h after attracticide exposure. In females, knock down was ≥ 2.5% and mortality ≥ 3.3% after pairing with intoxicated males. Leg autotomy in males was at least 73% in C. rosaceana and ≥ 41% in P. pyrusana, 24 h after attracticide exposure; whereas it was only ≥ 10% among females of both species after pairing with intoxicated males. Moths exposed to an attracticide blank (permethrin-free) showed significantly lower effects in all parameters (0-3.3%). Fecundity and fertility were also significantly affected after pairing females with intoxicated males. There was no significant decrease in mortality, leg autotomy, and fecundity associated with age of the attracticide. Results suggest a high potential for the use of attracticides against these two tortricid species.