Use of Wild Crucifers as Trap Crop for the Control of Plutella xylostella in Broccoli (Brassica oleracea var. italica)
Humberto Carranza Bazini (Guatemala); Stephen Weller (US)
This study focused on determining if wild crucifer species attract Plutella xylostella moths, and to evaluate them as potential trap crops. Two completely enclosed (in anti-aphid cloth) test plots were established, one located at the “Centro Universitario de Oriente” (CUNSURORI) in the Department of Jalapa (October 1997 to February 1998), and the other at the ICTA station at Chimaltenango from (April to July 1997). A completely randomized design with 5 treatments and 10 replications was utilized. The wild crucifer species included Raphanus raphanistrum (mustard, wild raddish), Brassica rapa = Brassica campestris (mustard, white mustard, “mostacilla”), Brassica napus (mustard, wild beet), Brassica nigra (“castilla” mustard, “colocha” mustard) and Brassica oleracea var. italica (broccoli) as the control. Approximately 250 adult laboratory-reared P. xylostella moths were released into each of the enclosures at the time broccoli was transplanted. Counts of eggs, larvae and pupa/plant were taken twice a week from the transplant date until the beginning of harvest operations.
The objective of this study was to determine if wild crucifer species attract Plutella xylostella moths, and to evaluate them as potential trap crops.
Results indicate that P. xylostella prefers B. napus to deposit eggs and complete the larval and pupal stages, with a general mean of 30 P. xylostella eggs per plant, surpassing by 53% the general P. xylostella mean found on broccoli. B napus was also the species that hosted more P. xylostella larvae and pupa, surpassing broccoli by 60% and 51%, respectively. Compared to the rest of the wild crucifers, B. napus was also statistically more attractive to Plutella xylostella; however B. nigra and B. rapa also showed acceptable attraction values and were superior or similar to broccoli's attracting capacity. Further evaluation of B. napus as a potential trap crop under field conditions has begun by H. Carranza Bazini (ICTA) and is reported in this annual report. Studies will also be designed to further evaluate several spatial distribution of B. napus in the field in order to maximize its potential as a trap crop. B. nigra and B. rapa also have potential as trap crops and will be evaluated in the eastern areas of Guatemala where they are most prevalent.