FIELDAND
FORAGE
CROPS
FIELD
The information and recommendations in this newsletter are applicable to
North Carolina and may not apply in other areas.
As of May 16, I have not seen or heard of thrips causing significant damage to this year's cotton crop. Our cotton crop and insects, in general, are off to a late start. However, some high levels of thrips have been reported in Georgia, mostly adults invading slow-growing seedlings.
A reduced rate of an at-planting insecticide is advised for the treatment of thrips. Last week's advice (i.e., the need for an at- planting insecticide as some planting continues into the final third of May) still holds. Much of our cotton is just coming into the thrips-vulnerable (expanded cotyledon) stage. Also, migrating adult thrips populations can increase rather dramatically over a short period of time. Although at this time of year, the insecticide rate can be cut by 40 percent due to the shorter anticipated time in which the seedling must be protected from thrips damage (quicker plant growth and typically declining thrips populations in early June). This at-planting insecticide treatment should not abandoned.
Continue scouting on a weekly basis for live thrips and their
damage. The terminals of 25 to 50 randomly-selected, widely-
scattered plants can be picked for closer inspection and evaluated
for both crinkled or possum-eared leaves. The presence of
immature thrips should also be confirmed prior to remedial
treatment. Pay particular attention to the youngest leaves as
older leaves indicate little about the present situation. Again,
magnification via a 15 to 30x hand lens may be required to find the
tiny, wingless, immature thrips. As mentioned in last week's
newsletter, several seedlings may carefully picked and rapped
sharply against either a white or a dark flat surface (an index
card or a shallow box will work). A treatment threshold of 2
immature thrips per plant is suggested.
At present, no reports of significant or even moderate insect
problems on cotton in North Carolina have been brought to my
attention. Plant bugs should be only a minor or non-existent
problem, except for a few isolated areas in several northeastern
North Carolina counties. Natural control of aphids (2 mummifying
parasites and a fungus, along with predators such as lady bird
beetles) has been excellent for the last 6 years, and approximately
6 percent the state's cotton acreage has been treated for
June/early July budworms during the last 4 years. I will attempt
to remain informed of potentially-developing insect problems as
they occur.
Some of our early cotton scouting schools are now being scheduled; more details will be provided in the coming weeks.
Hoke, Robeson and Scotland counties: June 19 at 10:00 a.m. at the O.P. Owens Center. Contact David Morrison, Area Agriculture Agent, Scotland County, for more information.
Craven County and Cove City area: June 23 at noon. Primarily offered for consultants and their scouts, although everyone is welcome. Contact Curtis Fountain, Area Specialized Agent (Cotton), Craven County, for more information.
Jones, Onslow and Craven counties: June 23 in the afternoon or evening, probably in Jones County. Contact Curtis Fountain for more information.
Sampson, Cumberland, Johnston, Harnett and surrounding counties: June 24 at 9:30 a.m. at Fann's Restaurant (6 miles from Spivey's Corner on Highway 13). Contact Bill Ellers, Agricultural Extension Agent, Sampson County, for more information.
Pitt County: June 25 at 9:30 a.m. at the Pitt County Agriculture
Center. Contact Sam Uzzell, Agricultural Extension Agent, Pitt
County, for more information.
Peanuts are going in the ground rather late this year. One
positive aspect to the delay in planting is thrips are usually less
severe on late-planted peanuts. Late-planted peanuts appear to be
attacked by fewer thrips and the warmer temperatures usually help
to get the peanut crop up and growing, thus avoiding some of the
thrips damage. If there was ever a time to consider omitting your
at-plant insecticide and taking a wait and see approach, it is
this year. However, it is important to be prepared to scout for
thrips injury and to apply a foliar insecticide if more than 25
percent of the leaflets show signs of thrips injury. Growers with
little or no experience in scouting for thrips may consider the
option of leaving a few streaks without the at-plant insecticide to
get a feel for this thrips management option.
A few reports have been received from eastern North Carolina of
adult vegetable weevils damaging tobacco. The adult weevils feed
at night on the stems and leaves of plants, usually near the field
margins. Damage to plants can be extensive. The threshold for
this pest is 5 percent of plants heavily damaged or killed.
However, spot treatments with insecticide along the damaged edge(s)
of the field may be adequate since these pests do not fly and move
only slowly into fields from the margins. For the best results,
insecticide treatments should be made in the late afternoon or
early evening. Growers may have to wait for two or three days
before new damage.
Reports and observations indicate that flea beetles are a problem for many growers in the central Coastal Plain and elsewhere. It is difficult to determine whether beetle numbers are higher than average or whether problems are more a result of growing conditions. Tobacco growing slowly during cool weather tends to accumulate flea beetle damage. This magnifies the apparent damage.
The treatment threshold for flea beetles is an average of four or
more beetles per plant. If tobacco continues to grow slowly and is
less able to compensate for beetle damage, growers should use their
judgement regarding the threshold. However, there is probably no
justification for treating with insecticide at less than 2 or 3
beetles per plant under any circumstances. Flea beetles are not
typically a significant problem once tobacco begins to grow rapidly
at about four weeks following transplanting. One other note,
growers who have used the insecticide Admire for the first time
this year may find flea beetles on the plants but see little damage. Admire
causes the beetles to be lethargic for some time before they die,
thus, they may still be on the plants but are causing little or no
damage.
Web page last updated on May 19, 1997 by Stephen J. Toth, Jr..
