Aphidoletes aphidimyza (Diptera: Cecidomyiidae). The aphid midge, Aphidoletes aphidimyza, is a cecidomyiid fly whose larvae are effective predators of aphids. Aphidoline biological control agent contains the predatory midge, Aphidoletes aphidimyza. This voracious midge lays its eggs in colonies of aphids, and the. Aphidoletes aphidimyza is gall midge whose larvae feed on over 60 different species of aphids. These gall midges are mainly used to control aphid colonies.
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The aphidophagous midge Aphidoletes aphidimyza Diptera: Cecidomyiidae is used in biological control programs against aphids in many crops. Short-term trials with this natural enemy demonstrated that that females prefer to oviposit among aphids colonizing the new growth of plants, leading to differential attack rates for aphid species that differ in their within-plant distributions.
Thus, we hypothesized that biological control efficacy could be compromised when more than one aphid species is present. We further hypothesized that control outcomes may be different at different crop stages if aphid species shift their preferred feeding locations. Here, we used greenhouse trials to determine biological control outcomes using A. At all plant stages, aphid species had a significant effect on the number of predator eggs laid. More eggs were found on M.
This translated to higher numbers of predatory larvae on M. In contrast, control of A. An additional experiment demonstrated control of A. Our study illustrates that suitability of a natural enemy for pest control may change over a crop cycle as the position of prey on the plant changes, and that prey preference based on within-plant prey location can negatively influence biological control programs in systems with pest complexes.
Careful monitoring of the less-preferred pest and pahidoletes relative position on the plant is suggested. Although multiple prey species can potentially have positive outcomes for biological control programs using natural enemies [ 1 ] the reverse can also be true e.
Negative outcomes can occur through preferential attack of predators on one herbivore in a food web, deflecting predation away from other pests [ 3 ]. Interestingly, this phenomenon can be mediated by preferred feeding locations of different prey species, rather than an inherent apihdimyza of the natural enemy for one prey type over another.
For example, the presence of the bird-cherry oat aphid, Rhopalosiphum padidecreases the efficacy of lacewings for controlling the Russian wheat aphid, Diuraphids noxiaas a direct result of R.
Within the time-scale of a crop cycle, such unbalanced predation due to within-plant distribution differences of aphid species could lead to apparent aphidmyza. Specifically, repeated attacks on the preferred pest lower the fitness of the first pest species, while simultaneously resulting in reduced control apbidoletes increased fitness of the second aphido,etes 34 ], leading to differential species control.
In systems where multi-species pest outbreaks are common e. Otherwise, failure of biological control for one or more species may occur. Concerns about failure of biocontrol programs is cited as one reason growers hesitate to adopt this pest control technique [ 6 ]. Aphidoletes aphidimyza Rondani Diptera: Cecidomyiidae is a commercially available natural enemy of aphids Hemiptera: Aphididae that is released in a surprisingly broad array of crops.
These include certain field crops e. In greenhouses, it is mostly released in crops such as pepper and tomato, potted ornamentals, and woody ornamentals [ 7 ]. However, a collection of previous research demonstrates that A. Specifically, Jandricic et al. These results suggest that M. Currently, however, the ability of A.
Extrapolations from oviposition-preference studies of predators alone cannot be relied upon, since factors such as prey suitability aphidoleted. Further complicating biological control in a program relying on a predator with prey preferences based on prey feeding locations is that within-plant prey distributions can change over time. Previous greenhouse studies show that aphids often apbidimyza up the plant when the plant becomes reproductive [ 212223 ].
A greater understanding of how a specific natural enemy responds to different pest distributions is needed if a biological control program is to be reliable over entire cropping cycles. This is especially needed situations where crops are of high value, where multi-species outbreaks occur frequently, and where crop cycles are short—all descriptions of greenhouse floriculture crops. Thus, the aphidoletez of this paper were to determine 1 how distributions of our model aphid species changed when infesting a greenhouse ornamental crop at different growth stages; 2 the response of A.
Studies were of longer duration than Jandricic et al. These results are then aphidimhza to practical aphid control in floriculture greenhouse crops.
Mixed clonal populations of both aphid species M. Adult aphids for all experiments were selected directly from colonies, and were therefore of unknown age. Pansies were chosen as they are readily accepted as hosts by both aphid species, and are aphidoletew type of spring bedding crop that regularly sees aphid infestations in commercial operations. Victoria, BC, Canada for all experiments.
Upon receipt, pupae were placed in emergence cages as described in Jandricic et al. Adult midges aphidolehes used instead of pupae to provide better management of the actual number of adult flies released. Adult midges were not used in experiments until ca.
For each experiment, adult midges were collected from emergence cages with a mouth aspirator using glass vials to prevent midges from being injured due to static electricity. A subsample of 50— individuals was also taken from the A. The average sex ratio over experiments in Section 2. However, a lower ratio of females was seen in the experiment assessing M. Plants were grown as in Jandricic et al.
Pansies were generally free of any additional ornamental pests e. Pansy crop stages tested apjidimyza vegetative, budding, and flowering produced under natural day length. Plants were considered vegetative as long as new growth at the meristem was not producing buds at the time of A. To be considered budding, plants had to have at least one distinct bud forming at the apical meristem with buds being developed enough to have distinct petal tissue. To test the flowering stage, aphidooletes potted for ca.
See Table 1 for details on experimental set-up. To determine what effect plant growth stage has on aphid distributions and A. This experimental design was repeated across three stages of plant growth: Experiments at different stages of plant growth were conducted separately due to experimental design constraints.
Experiments were conducted across 2—3 greenhouse compartments, each in either spring or fall to provide similar growing conditions. Details of experimental set-up of plant growth-stage experiments in greenhouse GH compartments.
There were two types of aphid infested plants within each compartment: These plants were then subjected to one of two treatments: Aphid species were not combined on the same plants since this would complicate choice results of the predator, and because this rarely occurs in commercial greenhouses ornamental crops. Specifically, multiple aphid species infestations can occur simultaneously within the same crop within the same greenhouse, but they hardly ever colonize the same plants [ 26 ].
To produce aphid infested plants, separate plants received either three adult M. Based on previous experiments, starting densities would result in ca. Aphids were added to the center of plants by fine brush and allowed to naturally distribute and reproduce on plants in the greenhouse for 1 week prior to the start of experiments day 0. Aphid infested plants were then placed in one of two locations: On day 0 of all experiments, adult A.
Thus, the same A. Predators were released at the center point of each grid of plants on each bench, as in Jandricic et al. The total release rate used per compartment was 2.
This is an intermediate rate among those that have been found effective in previous testing in greenhouse crops see [ 27 ]. Ventilation fans were turned off overnight to promote midge settling in the crop. To increase relative humidity RH to promote oviposition see [ 28 ]mist emitters, located beneath each bench, were operated for 5 min of every 60 min for the duration of the experiment. Aphid and predator numbers were then sampled across three separate dates in all four treatments see Insect Sampling, below, Section 2.
To determine if A. The number of infested plants was doubled within the A. As individuals of A. On day 9, counts of large larvae still foraging on the plant were made, as were counts of any small larvae present from later oviposition.
Though larval sizes were not distinguished during counts, the majority of larvae sampled on days 9—11 were large e. For vegetative plants, these locations consisted of bottom, middle, or top leaves or the center growing point of the plant.
The respective leaves were ca. Aphids were rarely found on mature, vegetative stem tissue. In the first compartment sampled with plants that were in the budding stage, aphids and A.
However, for the following two compartments, insects on flower buds were tallied separately to characterize the attractiveness of this plant organ this data is reflected in the distribution graphs in Section 3. For flowering plants, locations of flower buds, fully open flowers, and senescing flowers i. Average temperatures in the research greenhouse compartments from the point of A. In all cases, conditions in the cage were extremely close to ambient conditions in the greenhouse, and thus are not reported separately.
To analyze the initial within-plant distributions of our aphid species at different plant growth stages Section 3.
Aphidoletes. Aphidimyza: Pests Attacked over 60 species of aphids.
Plant stratum, aphidoleyes species and their interaction were tested. Proportions were used rather than numbers to facilitate comparisons between species even when at vastly different densities. The medium stratum was selected for exclusion because it generally contained the lowest number of aphids.
We also specified plant as the repeated measure from which location measurements were taken. The entire analysis was repeated with data subject to the empirical logit transformation, as recent simulations have indicated it may be an improvement over arcsine for proportions [ 29 aphidjmyza. However, we detected no significant differences in outcomes between the two transformations; the results of the arcsine are reported.
Predator response Section 3.