Preserving the utility of new and old management options will continue to depend on a thorough understanding of WCR biology, even as the ecological circumstances and geography of WCR problems become more complex.
Spotted Cucumber Beetle
Keywords Chrysomelidae, Coleoptera, crop rotation resistance, maize, mating, movement, nutritional ecology, ovipostion, semiochemicals, Zea mays. Introduction as a pest in Gillette, Today, it is the most im- portant pest of maize Zea mays L. Corn Belt. After emergence from overwin- This article reports the result of research only.
Mention of a pro- tering eggs, larvae feed on maize roots. Apart from maize, prietary product does not constitute an endorsement or recommenda- larval development to adult is also possible on a number non- tion for its use by the USDA, The University of Illinois, The Illinois maize grasses Oyediran et al. Spencer et al. During the that this review of WCR behaviour and ecology is undertaken.
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Annually alternating maize planting with that ment is faster than that of females Branson, Despite of a nonhost plant i. Writing male emergence period overlaps with that of females. After in the report of the State Entomologist of Illinois, Stephen males emerge, approximately 5—7 days of post-emergence de- A.
WCR females are sexually mature upon adult Forbes, Corn Belt, with some notable exceptions Levine et al. Subsequent to , rootworm-resistant volved in WCR reproduction. The major active The success of crop rotation highlights the importance of component of the WCR sex pheromone is 8R-methyl-2R- understanding pest biology to improve pest management. Yet, decenyl-propanoate Guss et al. The WCR sex pherom- even within an integrated pest management IPM frame- one was the first to be identified and synthesized from a work, broad adoption of annual crop rotation ultimately se- chrysomelid Guss et al.
A desire to avoid Reid, The same molecule is also the active component rapid resistance to rootworm-resistant transgenic maize hy- of the sex pheromone of the Mexican corn rootworm brids expressing insecticidal proteins from the soil microbe, Diabrotica virgifera zeae MCR ; the two closely-related sub- Bacillus thuringiensis Bt Vaughn et al. The rootworm IRM plan includes the use of nontrans- of gas-liquid chromatographic fractions of volatiles collected genic maize refuges within or adjacent to fields where a from virgin female WCR, southern corn rootworm Diabrotica rootworm-resistant hybrid is grown.
Refuges are sites where undecimpunctata howardi Barber SCR , and Diabrotica susceptible genotypes can survive. It is expected that Bt- longicornis. One active fraction was found for each species, susceptible refuge males will disperse throughout the transgenic corresponding to structurally known sex pheromones for crop and out-compete the relatively less abundant, but poten- WCR and SCR. Sex pheromones are probably not a repro- tially-resistant, transgenic-field males for mating opportunities.
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Global warming presents new challenges for maize pest management - IOPscience
Guss et al. Ball, Dobson and Teal characterized a slow hovering flight In the hours after adult emergence, young females crawl with the body held in a vertical orientation as a positive up nearby maize plants or fly short distances to nearby plants response to pheromone. The exposed area is hind legs rest on the substrate. If not immediately rejected, the WCR abdomen. During the pre- ceptive to males than those who were not. In the spotted cucumber However, Hammack noted con- bursa copulatrix and begin delivering the liquid spermatophore siderable calling-pattern variability between individuals; only components Tallamy et al.
In field studies using sticky traps baited with virgin cepted as a mate Tallamy et al. Lew and Ball females, Bartelt and Chiang could not identify any report that WCR antennal tapping quieted the female allowing calling pattern based on trap capture data. Once in copulo, the male bends mate-seeking males Hammack, Although unmated fe- his abdominal segments downward and his antennae cease males continued to call for several days in the Hammack moving and are folded backward over the male elytra. In SCB, study, an extended period of virginity for field females posterior folding of the antennae over the elytra is a sign that is unlikely given a normal abundance of males.
Several authors a spermatophore is being successfully transferred Tallamy report that calling females are rapidly mated Ball, ; Hill, et al. A high proportion of teneral females stroke the sides of the female with the mesothorascic legs; [i. Quiring dislodge him by anchoring his metathorascic legs under the tip and Timmins reported that Hairless, planar ovoid patches found were teneral When in copulo, the female may walk about and male flagellum Staetz et al.
There is also a sexual feed or groom; males have no opportunity to feed. The At its conclusion, the male may remain atop the female structure and distribution of sensilla on the male antennnae in a mate-guarding posture until she disturbs or dislodges him. Other studies the first hour of mating, and a pale pink spherical portion report pre-ovipositional periods ranging from Within 2. The fecundity-enhancing effect of mating was ob- Based on production of viable eggs, stored sperm crosses Krysan et al.
Clark Larger et al. Peak male mating activity of the Mississippi River. Branson et al. Surprisingly, mean spermatophore size It is speculated that old WCR females may remate if was not different between large 0.
By males 0. When males mated twice a day, mean initially pairing females with sterile irradiated males and spermatophore size was not different from that when only one later presenting untreated males, Branson et al. Depending on male size, deposition of the ovipositing. These Rarely, females with two spematophores are found Branson et al.
Spencer, unpublished data. Hammack characterized for the SCR Tallamy et al. Invoking a similar mechanistic behavioural and posture. When matings are terminated before sperm were chemical ecology-based approach, including attention to the transferred, Sherwood and Levine found that females fate of cucurbitacins bitter compounds that are strong had an increased likelihood of laying eggs compared with phagostimulants for diabroticite beetles of tribe Lupernini in unmated females.
However, interrupted females laid signifi- WCR mating studies, could yield valuable insights into the cantly fewer eggs than females from completed matings or intersection of WCR reproduction and cucurbitacin pharma- interrupted matings where some sperm were transferred.
Invasive Species Compendium
Studies by Sherwood and When females mated for just 1 h, an expected increase Levine and others provide evidence for male-contributed in egg development typically observed at approximately fecundity-enhancing substances. Females mated for 1 h laid Branson and Krysan con- tified Yapici et al. It may be possible to use molecu- cluded that females lay eggs wherever they are feeding.
Current in soybean Shaw et al. In retrospect, some of that in- IRM plans for rootworm-resistant transgenic corn hybrids in- jury was probably due to natural variability in WCR oviposi- corporate the assumption that mate-seeking refuge males will tional site selection Spencer et al. European studies out-compete the scarce transgenic field males for opportuni- of invasive WCR in maize and rotated crops reveal their pres- ties to mate with females emerging from transgenic corn. However, this occur- However, the literature contains little about WCR reproduc- rence is explainable based on normal patterns of movement tion in the field.
The maximum distance from which field and incidential oviposition; rotation resistance is not present males respond to calling females, or the impact of calling fe- Kiss et al. Knight et al.
Methods for the Study of Pest Diabrotica
The effect of high versus low adult density soybean from South Ontario, Canada. In Other significant questions are also related to assumptions studies of rotation-resistant WCR in Illinois, Rondon and about mating and refuge function. How frequently do males Gray found gravid females in maize, soybean, oat mate in the field and how long must the refractory period be- Avena sativa L.
Schroeder et al. Do males seek mates when they are incapable of de- adults and found eggs in maize, soybean, wheat and wheat positing a full spermatophore? How would a limited male mat- double-cropped with soybean, although egg densities were ing potential affect IRM assumptions for transgenic maize highest in corn.
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Pierce and Gray b determined that systems? In what proportion and at what age do fe- fields. An earlier Iowa study by Gray and Tollefson males in the field remate, if ever?
Pierce and Gray b concluded that the rotation-resistant WCR oviposits in maize, soybean, oat stubble and alfalfa. Thus, the lack of a distinct ovipositional preference among rotation-resistant WCR prob- Oviposition ably contributes to widespread oviposition in all crops. Bayar et al. Under normal conditions, females passed have enabled a broadened ovipositional host range.
Kirk through a day pre-ovipositional period, eggs were then et al. Lance, Because the homogenates were deactivated Mean lifetime fecundity of once-mated WCR females held by sorbate, a bacteriostatic agent, most treatments were prob- under realistic, but close to optimal nutritional conditions, ably active due to enhanced levels of CO 2. Elliott et al. WCR do not dig burrows Kirk, If diet is supplemented, very high mean fecundity [i.
Adult emergence or in- Seevers, ; Naranjo, b; Isard et al.
Witkowski trafield flight activities, for which expression is probably et al. Dobson and Teal described how peaks of greatest flight occurring during the hours just before evening and nighttime temperatures near thresholds for bee- sunset and the hours just after sunrise. An expected flight activity. Naranjo b used a vertical flight mill de- period of NCR activity was shifted to the next morning where sign Wales et al.
Ball found that adult WCR insecticide diazi- Although the activity peaks and troughs in this well-replicated non sensitivity varied with photopheriod; field-collected study are not distinctly resolved, bimodal morning and evening WCR were most vulnerable to insecticide from midday to peaks of flight activity remain evident.
Where populations are late evening. Extrapolation of captures from eight malaise traps positioned at the borders of a 1.