Vol. 16—1962 - NorthEastern Weed Science Society

u.s. #1 potatoes and weed control estimates are shoWnin table 1. The sources
of the herbicides and their chemical compositions are in the appendix.
Table 1. Average yields of Katahdin potatoes and weed ratings from posthilling
herbicide applications (R.I. 1960).
!J:J!A Bu/A WeedRat7n gs*
Active U.S. 8/24 60 Annual
Herbicide Toxicant # 1 Ladyatthumb Grasse$
1. Falone spray 4 364 7.4 8.8
2. Falone gran. 4 376 8.6 5.5
3. DNBPgran. 3 379 8.4 4.0
4. Dalapon gran. 2.5 364 7.4 3.8
5. Alanap gran. 4 364 8.0 7.9
6. Dalapon spray 2.5 358 6.5 2.0
7. Zytron spray 10 403 9.4 9.5
8. Zytron gran. 10 387 8.8 7.4
9. Trietazine spray 2 399 9.5 4.8
10. Tr~etazine gran. 2 373 9.4 6.0
11. Casoron 4 323** 9.4 3.2
12. Casoron gran. 2 329** 9.6 2.2
13. No treatment 399 7'.1 2.0
14. Dalapon &DNBPgran. 2.5 + 3 342 9.0 3.8
15. Falone &DNBPgran. 3 +4 361 9.0 7.9
16. Alanap &Falone gran. 4 +4 352 8.8 8.5
ISD at 0.05 56
*10 =no weeds, 1 =no control **some physical damage to tubers
167
Someweeds were already established on the crowns of the hills previous
to applying the herbicides. These were disregarded in the estimates of percent
weed control. Only the weeds which sprouted from the freshly stirred soil
after hilling were rated. The annual grass popUlation was mostly foxtail and
barnyard millets from the broadcast seeding. Ladysthumbwas the prevalent
broadleaved weed.
The following chemicals produced a marked reduction of the ladysthumb populationl
zytron spray at 10 lb/A, trietazine spray or granular at 2 lb/A, and
casoron at 2 and 4 lb!A. The casoron which was applied before hilling caused
considerable pitting'of the potato tubers. Granular DNBPalone, or combined
either with dalapon or falone, produced fair control of ladysthumb. Alanap,
falone or dalapon alone were not effective in preventing growth of this weed.
Results with the herbicides that usually inhibit grasses were disappointing
in the control of the millets. Falone spray at 4 lb/A of toxicant gave
good control while the granular preparation was only fair. A combination of
granular alanap and falone each applied at a rate of 4 lb/A produced a satisfactory
reduction of the annual grasses. Dalapon at the 2.5 lb/A was ineffective
during the 1960 season. Likewise 2 Ib/A of trietazine was not as effective
as in former seasons. Zytronspray at 10 lb/A produced a marked reduction
_ ~ __ 11 ... _.L _ ,. __ • ••