No abstract

Mealy plum, Hyalopterus pruni, and leaf-curl plum, Brachycaudus helichrysi, aphids are the primary arthropod pests in orchards that produce dried plums (i.e., prunes). The sexual stage of their respective lifecycles occurs on prune trees in the fall, during which time males respond to sex pheromones produced by oviparous females. Air-entrainment collections confirmed that oviparous H. pruni and B. helichrysi emitted combinations of (4aS, 7S, 7aR)-nepetalactone and (1R, 4aS, 7S, 7aR)-nepetalactol. The responses of H. pruni and B. helichrysi to these compounds in ratios of 1:0, 0:1, 1:1, 2.6:1, 3.4:1, 5:1, 7:1, and 0:0 (no-pheromone control) using water traps were determined in field experiments conducted in prune orchards during the fall. The greatest number of male H. pruni was caught in traps releasing a 1:1 ratio of (4aS, 7S, 7aR)-nepetalactone and (1R, 4aS, 7S, 7aR)-nepetalactol, while male B. helichrysi were caught in similar numbers in traps releasing any of the two-component ratios tested. There was no evidence that any of the pheromone treatments influenced trap catches of gynoparae of either species. Results suggest that addition of sex pheromone lures increases trap catches of male H. pruni and B. helichrysi, and that this approach may improve monitoring and management of these pests in prune orchards. Knowledge gained from this study contributes to the understanding of the ecology of insect pests in prune orchards.

Three isofemale lines of Myzus persicae (Sulzer), two lines collected from and reared on a brassicaceous host, and one line collected from and reared on a malvaceous host, were evaluated for their efficiency of transmitting Zucchini yellow mosaic virus (family Potyviridae, genus Potyvirus, ZYMV). In the first experiment, the transmission efficiencies of two clones from Brassicaceae (B1 and B2) were 52.0 and 60.8%, respectively, and these transmissions were not significantly different. In a second experiment, the transmission efficiencies of the clone on Malvaceae (M1) and clone B2 were significantly different at 35.6 and 55.7%, respectively. Further experiments evaluated host-related mechanisms that may have contributed to the differential transmissions observed between clones M1 and B2. Studies on short-term feeding showed that aphids continuously reared on okra, Abelmoschus esculentus (L.) Moench (malvaceous host), and those that were reared on okra and allowed a 24-h preacquisition feeding period on mustard, Brassica juncea (L.) Czern (brassicaceous host), had significantly lower transmission than aphids continuously maintained on mustard. Aphids reared on mustard and allowed a 24-h preacquisition feeding period on okra had intermediate transmission efficiency. In long-term host association studies, we found that aphids reared on mustard had significantly higher transmission efficiency than those reared on okra, and aphids reared first on okra and then switched to mustard had a transmission efficiency that was intermediate and not significantly different from the other two treatments. Our study reveals the existence of intraspecific variation in the transmission of ZYMV by M. persicae, and it suggests that to accurately assess the transmission capability of ZYMV by this species, multiple clones should be examined. Furthermore, the host plant on which the aphid is reared as well as the host plant on which it feeds just before virus acquisition contribute to ZYMV transmission efficiency of M. persicae.

The direct current electrical penetration graph (DC‐EPG) technique was used to identify stylet penetration behaviors of Myzus persicae (Sulzer) (Hemiptera: Sternorrhyncha: Aphididae) that are related to successful acquisition and inoculation of the non‐persistently transmitted potyvirus, Zucchini yellow mosaic virus (ZYMV), to melon, Cucurbita pepo L. (Cucurbitaceae). Stylet penetration behaviors of two sources of M. persicae that differ in their ZYMV transmission efficiency were examined to determine if behavioral differences were related to their differing ZYMV transmission efficiencies. Successful acquisition of ZYMV by M. persicae was significantly related to longer total time in intracellular subphase II‐3 of potential drops. Successful inoculation of ZYMV by M. persicae was related to a greater number of intracellular punctures, shorter durations of intracellular punctures, and longer total time in intracellular subphase II‐1. Of these variables that were related to ZYMV transmission, the two aphid sources differed in the total time spent in subphases II‐1 and II‐3. These results suggest that the differences in ZYMV transmission efficiencies between the aphids may be at least partially caused by behavioral differences during stylet penetrations of the host plant tissue, specifically behaviors that occur during intracellular punctures.

Three isofemale lines of Myzus persicae (Sulzer), two lines collected from and reared on a brassicaceous host, and one line collected from and reared on a malvaceous host, were evaluated for their efficiency of transmitting Zucchini yellow mosaic virus (family Potyviridae, genus Potyvirus, ZYMV). In the first experiment, the transmission efficiencies of two clones from Brassicaceae (B1 and B2) were 52.0 and 60.8%, respectively, and these transmissions were not significantly different. In a second experiment, the transmission efficiencies of the clone on Malvaceae (M1) and clone B2 were significantly different at 35.6 and 55.7%, respectively. Further experiments evaluated host-related mechanisms that may have contributed to the differential transmissions observed between clones M1 and B2. Studies on short-term feeding showed that aphids continuously reared on okra, Abelmoschus esculentus (L.) Moench (malvaceous host), and those that were reared on okra and allowed a 24-h preacquisition feeding period on mustard, Brassica juncea (L.) Czern (brassicaceous host), had significantly lower transmission than aphids continuously maintained on mustard. Aphids reared on mustard and allowed a 24-h preacquisition feeding period on okra had intermediate transmission efficiency. In long-term host association studies, we found that aphids reared on mustard had significantly higher transmission efficiency than those reared on okra, and aphids reared first on okra and then switched to mustard had a transmission efficiency that was intermediate and not significantly different from the other two treatments. Our study reveals the existence of intraspecific variation in the transmission of ZYMV by M. persicae, and it suggests that to accurately assess the transmission capability of ZYMV by this species, multiple clones should be examined. Furthermore, the host plant on which the aphid is reared as well as the host plant on which it feeds just before virus acquisition contribute to ZYMV transmission efficiency of M. persicae.