Cabbage Integrated Pest Management : An Ecological Guide.

Cabbage Crop Development2.2 Susceptibility of growth stages to cabbage pestsWhether various pest and disease species that attack cabbage plants will cause yield loss dependspartly on the growth stage of the plant. Injury to the older leaves at a late stage in crop development forexample, will not influence the final yield. Spraying a fungicide to control a slight Alternaria leafspotinfection occurring at the older leaves, is simply a waste of money.For fresh market cabbages for example, the quality could be reduced if even slight injury occurs on thewrapper leaves or the head. In earlier stages, stages 1 to 6 however, the wrapper leaves are not yetpresent and injury need only be prevented if a loss in head weight (yield) is expected. The cabbage plantcan compensate for a lot of injury by producing more leaves.In the TOT and FFS, studies on defoliation and removal of the growing point can be conducted to obtaininformation about compensation ability of the cabbage plant. An example is given in the box below.Compensation study result from Ban Nongkeo, Vientiane, Lao PDRDuring a field study by farmers of the village of Ban Nongkeo, farmers defoliatedcabbage plants for 25% and 50% at both 14 and 28 days after transplanting(DAT) and looked at resulting yields compared to an undefoliated control.Defoliation simulates the effect of leaf damage due to leaf-eating insects like diamondbackmoth.L A O SFarmers found that all 4 defoliation treatments had no effect on yield compared to the control,in fact, yields were the same or slightly higher in the treatments. Farmers concluded thatlimited defoliation in the first month after transplanting did not affect yield.(from: FFS on IPM in tomato and cabbage, Lao PDR, Nov 98 – Mar99).Some pests are present throughout the season and can affect cabbage at any growth stage. They willonly affect the quality or yield at susceptible growth stages. Damage, and impact of damage on yield, willalso depend on the cabbage variety grown, and other elements of the ecosystem like natural enemies,weather conditions, fertilizer, water availability and so on.Always analyse all components of the agro-ecosystem andtheir interactions when making crop management decisions!The following table (2.2) shows when potential injury from common cabbage pests and diseases mayoccur at specific growth stages. Please note that these are general values. There may be considerabledifference in each region!Cabbage Ecological Guide - 20008