RESULTS AND DISCUSSION

 Excessive rainfall, delayed planting, and fall armyworm injury were

the major differences that we observed between the years of 1989 and

1985 through 1988. Rainfall from 21 May to 27 June 1989 was 20 inchs.

Rainfall during the tropical corn growing season of 1989 can be compared

with the rainfall for 1988 (Fig. 1). Only two fields of X-304C were

planted early in North Florida that we knew of, the rest, including the

tropical corn hybrid yield trial, were delayed until after 27 June.

 The yield of the early planted tropical corn in 1989 was 61 bu/A at

NFREC and 65 bu/A in the farmers field compared to 94 bu/A yield average

for 1986, 1987, and 1988 at NFREC. Fall armyworm damage in the 1989

early planted X-304C was only noticeable on leaves about the same as

observed in 1985 to 1988. The 1989 late planted, fall armyworm infested

X-304C (planted 29 June) yielded 42 bu/A. Therefore, we have suggested

a window between 24 May and 10 June where fall armyworm damage is at a

low risk.

 Under severe infestations as observed in 1989 late planted tropical

corn, the fall armyworm will skeletonize leaves in early instars or

produce ragged holes in later instars and eat the tassels and silks. We

have not observed much fall armyworm damage on the ears or stems of the

ears of X-304C, but grain fails to develop from lack of pollination.

Percent tasseling and silking curves for early planted X-304C in

relation to day of year for 1988 show little observable fall armyworm

damage, but percent tasseling and silking curves for late planted X-304C

in 1989 show extensive fall armyworm damage. The 1989 change in

tasseling pattern was observed on 240 day of year (28 Aug) when fall

armyworm consumption of tassels made it appear that tasseling had

 5