nasike watakila (1)-1-2.docx

232 distribution the cabbage aphid is native to

Info icon This preview shows pages 4–6. Sign up to view the full content.

View Full Document Right Arrow Icon
2.3.2. Distribution The cabbage aphid is native to Europe, but now has a worldwide distribution (Kessing and Mau 1991). Severe damage to various plants in the family Brassicaceae has been reported in many areas including Canada, The Netherlands, South Africa, India and China. The cabbage aphid is widely distributed throughout the U.S. and has been found to be more of a pest in the southern states (Carter and Sorensen 2013). 2.3.3. Identification The cabbage aphid is difficult to distinguish from the turnip aphid (Lipaphiserysimi (Kaltenbach)). The cabbage aphid is 2.0 to 2.5 mm long and covered with a grayish waxy covering, but the turnip aphid is 1.6 to 2.2 mm long and has no such covering (Carter and Sorensen 2013). The cabbage aphid and green peach aphid (Myzuspersicae (Sulzer)) can be confused when they are both found feeding on cabbage plants. However, they have distinguishing morphological characteristics. For instance, the cabbage aphid is waxy with short cornicles. On the other hand, the green peach aphid lacks a waxy covering, and has long cornicles (Opfer and McGrath 2013). Moreover, green peach aphids mainly attack cabbage before heading (after transplanting, the cabbage seedling starts producing leaves, and eventually the cabbage plant begins to produce a small, tight head at the center of the group of leaves) begins, but cabbage aphids may attack the crop at any stage (Elwakil and Mossler 2013). 2.3.4. Hosts The cabbage aphid has a host range restricted to plants in the family Brassicaceae (=Cruciferae), which include both cultivated and wild cruciferous crops (Gabrys et al. 1997).
Image of page 4

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Major economically important host crops where significant losses have been found include cauliflower (Brassica oleracea L. var. botrytis L.), brussels sprouts (Brassica oleracea L. var. gemmifera DC), broccoli (Brassica oleracea L. var. italicaPlenck) cabbage (Brassica oleracea L.), oilseed rape (Brassica napus L.) and other members of the genus Brassica (e.g., Indian mustard (Brassica juncea L.), white mustard (Sinapis (= Brassica) alba L.), black mustard (Brassica nigra L.), toria (Brassica rapa L.). It also attacks Chinese broccoli, Chinese cabbage (Brassica rapa, subspecies pekinensis and chinensis), radish (Raphanussativus L.) and kale (Brassica alboglabra L.H. Bailey) (Kessing and Mau 1991). Cabbage aphid is an especially big problem in broccoli and cabbage production (Opfer and McGrath 2013). Life History Aphids can reproduce two ways. In warm climates (e.g., in Florida and Hawaii), females give birth to female nymphs without mating. In this case, an aphid colony consists of females only. This occurs during warmer periods in temperate climates as well. In temperate climates, however, the mode of reproduction changes during the autumn as temperatures begin to drop. In response to low temperature or decrease in photoperiod, males are also produced (Blackman and Eastop 1984). Mating takes place and females lay eggs. The egg stage is the overwintering stage of aphids. Generations are overlapping, with up to 15 generations during the crop season (Hines and Hutchison 2013). The total life cycle duration ranges between 16 to 50 days depending on temperature. The life cycle is shorter at higher temperatures (Kessing and Mau
Image of page 5
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern