Weed Science

TPSS 481


Joseph DeFrank

Semesters taught:

Fall 2014, Fall 2015, Fall 2016


The goal of the lecture portion is to provide students with an understanding of weed biology and ecology as related to characteristics associated with weediness, and an understanding of the principles of weed control, properties, action, and uses of herbicides.

The goal of the Weed Science Laboratory is to provide hands on experience for the management weeds with both chemical and biological methods. The main object of the lab is to provide students with skills needed to take on the job of weed management in variety crops produced in Hawaii using both conventional and no-tillage methods.

Skills and knowledge to be acquired:

Students will gain an understanding of characteristics associated with weeds, weed control methods and herbicides, and to use this knowledge to support their analysis of weed problems and formulate control strategies. An important skill that students will take away from the lab section is the ability to understand pesticide labels and deliver an effective dose of crop protection chemicals using a variety of both large and small equipment. Students will also obtain an understanding of IPM methods for weed management.

Computer skills to be acquired:



TPSS 200 and CHEM 152, or consent

Cross-Listed courses:

PEPS 481


Weed Science: Principles and Practices. (3rd edition), Ashton and Monaco. 1991.

Handbook of Hawaiian Weeds (eds. E. Haselwood and G. Motter this text is currently out of print), company literature on spray system parts and agricultural spray pumps.

Recommended text for the lab is "Wayside Plants of the Islands" (W. Whistler).

Films and videos:

Vegetable Farmers and their weed-control machines; No-till farming

Guest Speakers:

Dr. Philip Motooka

Field Trips:

NB Field demonstrations conducted at Magoon Greenhouse facility

Course organization:


  • Losses from weeds and types of damage
  • Weed classification, ecology, adaptations for weediness
  • Weed propagule longevity, dormancy, germination
  • Concept and examples of noxious weeds
  • Weed control methods: cultural, crop competition, mechanical, biological, chemical
  • Herbicide formulations and applications
  • Herbicide behavior in plants: absorption, translocation
  • Herbicide behavior in soils: adsorption, degradation, leaching
  • Herbicide selectivity
  • Weed species/biotype shifts and herbicide resistant weeds
  • Action and uses of herbicides
  • Weed management strategies for some crops of Hawaii


  • Weed Identification and collection, grasses/ broadleaf and sedge weeds
  • No-tillage farming and allelopathy in agroecosystems.
  • Herbicide injury and diagnosis
  • Spray equipment: nozzles, pumps and specialized applications systems
  • Sprayer calibration, small sprayers, controlling spray drift.
  • Living sods for weed control in tropical cropping systems.
  • Pesticide labels and safety



General: Approximate values on course requirements

  Points % of Total
Lecture examination I 50 10 %
Lecture examination II 70 14 %
Lecture examination III 70 14 %
Lecture examination IV 80 16 %
Lecture student presentation/outline 30 6 %
Laboratory 200 40 %
Total 500

100 %


  Points available % of Final Grade
Weed I.D. quiz 30 15
Calibration homework 10 05
Calibration quiz 40 20

Written reports

1. Herbicide performance 20 10

2. Selected group reports

a) Oral seminar, group grade 10 05
b) Written report, group grade 10 05
Weed collections 30 15
Lab. Final 50 25
Totals 200 100


Relationship of points earned to final laboratory grade

200-181 4.0
180-161 3.0