The upper 30 cm of soil in a field infested with purple nutsedge (Cyperus rotundus L. #3 CYPRO) contained 4900 to 5100 corms and tubers/m2 6 weeks after soil rotovation and irrigation. The upper 4, 8, 12 and 16 cm of soil had 45, 79, 95 and 99%, respectively, of the corms and tubers. Lower depths of soil contained larger tubers with higher percent dry matter than the shallow depths. Of the total number of corms and tubers, 51% were from the parent population. At 6 weeks, only 15% of the total tuber and corm population were not connected to aerial parts. Tubers from the parent population had a higher fresh weight than those from the new population. Parent tubers occurred singly or in chains of up to eight tubers.

Bulbous oatgrass, a weed in parts of the United States and Europe, is an unusual grass, which forms corms at the stem base. Growth and development of this creeping perennial grass was investigated in the field and in pots outdoors. Under the mild climate of the Willamette Valley, Oregon, shoots emerged in early autumn. Plants grew vegetatively and formed corms during the winter and spring. Aboveground portions of the plant stopped growing and senesced in the summer. The absolute growth rate of the plants was highest in early May, shortly before the onset of flowering. In early May, the growth rate of corms was higher than that of the shoot.

A simple technique is described for rapid determination of weed seed, rhizome, corm, or bulb populations in soil. Soil samples were placed in nylon mesh bags. The soil was washed from the bags by machine leaving only a small residue including the desired propagules. These were hand separated and the soil population of a given plant species calculated. The total manipulation time per sample was approximately 10 min.

Multiple applications of several preemergence herbicides were evaluated for weed control and for phytotoxicity to gladiolus (Gladiolus X hortulanus L.) grown from cormels in 1984 and 1985. Oryzalin [4-(dipropylamino)-3,5-dinitrobenzenesulfonamide] consistently provided acceptable control of southern crabgrass [Digitaria ciliaris (Retz.) Koel. # DIGSP], goosegrass [Eleusine indica (L.) Gaertn. # ELEIN], and smooth pigweed (Amaranthus hybridus L. # AMACH) and had minimal effect on gladiolus plant growth even after four applications. Pronamide [3,5-dichloro (N-1,1-dimethyl-2-propynyl)benzamide], alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] provided erratic weed control and reduced yields of gladiolus corms.

Introduction. Small-scale bananaproducers in Tanzania are facing constraints caused by the destructiveactivities of the banana weevil (Cosmopolites sordidus Germar).Many currently used methods of addressing the problem are ineffective ortoo expensive for local farmers to implement. Materials and methods.A combination of two integrated pest management (IPM) tools (regulartrapping in combination with field sanitation) was tested at twofarmer-managed sites (Bujela and Kyimo) and one researcher-managedsite (SUA-Morogoro). Treated areas were surrounded by untreatedcontrol areas where no trapping and limited sanitation was done.Changes in population densities were estimated by the mark-recaptureprocedure and the Lincoln index. Results and discussion. Aftereight months, weevil populations in the cleaned and trapped areashad been reduced by 33% (Bujela), 33% (Kyimo) and 74% (SUA). Thechange in population sizes in the control areas differed greatly,possibly due to discrepancies in field management between farmers’ andresearchers’ practice. Trap types, areas and sites affected thenumber of weevils captured. Disc-on-stump (DOS) traps captured moreweevils than corm disc (CD) and pseudostem (PS) traps. Weevils respondedmore strongly to traps in the clean area at SUA compared with theother two sites, probably because the more rigid sanitation practicesat SUA meant that volatiles from the traps were less likely to bemasked by volatiles from surrounding residues. Conclusion.Regular trapping with field sanitation can greatly reduce populationsof banana weevils, but strict adherence to method execution is requiredin order to gain favourable results.