Contact Hours :  3 hours  of  lectures  per week plus  a 3 hour practical for a 13 week semester.

Course Content
 

  1.      Weed evolution and origin

  2.      Characteristics of weeds Definition of a weed in relation to
          occupation of disturbed habitats. Characteristics related to
          seed behavior - seed output, dormancy, seedbanks, longevity
          and periodicity of weed seed germination. Adaptation/
          characteristics related to plant growth rate - RGR of weeds
          versus crops, relationship between seed size and growth site,
          C3/C4 pathways and competitiveness weed crop mimicry.

  3.      Vegetative reproduction and methods of dispersal - vegetative
          propagules, advantages and disadvantages of vegetative
          reproduction to weeds, methods of seed dispersal

  4.      Weed identification - Weed identification keys. Weed
          classification. Importance of identification of young growth
          stages.

  5.      Weed crop interference - Definition of interference,
          competition and allelopathy. Types of competitiori. Effects
          of increasing weed density on crop biomass and economic yield.
          Period when weeks are present and length of weed free period
          effect on yield. Factors affecting weed crop competition -
          weed factors, crop factors and environmental factors.
          Allelopathy - true/functional, source and nature of
          allelechemicals.  Methods of studying allelopathy.

  6.      Biology of problem weeks in Zimbabwe - Cyperus esculentus
          protundus, Commelina benghalensis, Rottboellia
          cochinchinensis, Oxalis latifolia, Richardia scabra others.

  7.      Aguatic weeds of Zimbabwe - Water hyacinth, Kariba weed, water
          lettuce

  8.      Parasitic weeds in tropical crops - Striga spp, Electra
          vogelli, dodder. Biology - germination, attachment,
          stimulation and growth. Parasitic weed problems in Zimbabwe,
          general control strategies.

  9.      Poisonous plants of Zimbabwe - Datura spp, Solanum spp
          Ricinus communis, Lantana camarra, Cucumis spp etc.

  10.     Introduction to Weed Control methods - A brief outline of mechanical/chemical/biological cultural
            weed control methods.

Practicals
1. Weed identification using keys, and collection.

2. Effect of depth of burial on weed seed germination.

3. Effect of longevity of storage/soaking for various periods on
   weed seed germination.

4. Effect of dessication on survival of perennating  structures of
perenial weeds.

5. Crop weed competition experiment/allelopathy experiments.

6. Aquatic weeds and evaporation rates.