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SCES Mimeo Series 70-11
CITRUS EXPERIMENT STATION
LAKE ALFRED, FLORIDA
QUARTERLY CITRUS INSECT AND MITE OUTLOOK
CAUTIONARY NOTE: This Outlook is based on the assumption that weather beyond the
period of the current U.S. Weather Bureau 30-day Outlook will be normal. Therefore, the
forecasts given below cannot be viewed with the same degree of confidence as those in the
"Insect and Disease Summary" usually released twice each month by this Station.
Each pest has more or less regular periods of increase and decrease throughout the
year. Weather conditions (temperature, rain, humidity) may affect populations directly,
or indirectly through effects on predators, parasites and tree growth. Departures from
the average population level may be caused by conditions that occurred months before.
Other fluctuations may reflect recent weather changes. The latter influences can be
forecast only to the extent that weather forecasts are available.
RECENT SITUATION JULY THROUGH SEPTEMBER 1969
Several pests were at high levels of abundance during the period. Rust mite was the
pest of greatest concern to growers in all districts.
Rust mite reached a very high level on both leaves and fruit the first week of July.
Throughout the period populations approached or exceeded the highest levels attained in
the prior 18 years. Highest population was recorded for the last half of July when 42%
of fruits were infested and 62% of groves harbored heavy infestations. These figures
refer to the 56% of survey groves not treated for rust mite control within the 30 days
prior to inspection. The other 44% of survey groves had received treatment so were not
included in the calculations.
Citrus red mite and Texas citrus mite both attained their summer population peaks
early in July. However, populations were at low to moderate level throughout the period
and much below normal most of the time. Less than 18% of groves developed heavy infestations
Black scale was the only scale that attained a high population level and exceeded
normal abundance. It peaked at mid-July, at which time 24% of terminal twigs were in-
fested and 35% of survey groves had heavy infestations. Population gradually decreased
but was still above normal and moderately high at the end of September.
Snow scale continued to become more abundant in July and August than in any prior
month, then decreased slightly in September. Although heavy infestations occurred, they
were very localized. The statewide population was in the low range.
Whitefly population was much above normal throughout the period. It was in the high
range all July and in early August, then decreased until late September when it again
reached a high level. At the July peak, 72% of survey groves were infested and 9% harbored
Mealybug population was much above normal through August and was at high level during
July and early August. At the mid-July peak, 28% of groves had heavy infestations.
Yellow scale and Glover scale were slightly below normal in July and only moderately
abundant during the period. Purple and chaff scales were below normal and at low level.
Green scale, although of little importance and of limited distribution, was more abundant
than usual July through September.
GENERAL FORECAST OCTOBER THROUGH DECEMBER 1969
Rust mite: Population will continue in the high range until mid-November, then
gradually decrease to moderate level. Heavy infestations may be expected to develop in
15 to 20% of groves in all districts.
Citrus red mite and Texas citrus mite will gradually increase from current low levels
but are not expected to exceed normal abundance. Damage will be restricted mostly to
Black scale is expected to occur in above normal numbers but will not be of concern
to growers until spring.
Snow scale will continue to produce crawlers until cold weather suppresses activity.
Some spread to uninfested areas is likely due to transport of crawlers by picking crews
Whiteflies are expected in above normal numbers as flat, nearly transparent larvae
feeding on the undersides of leaves. Decrease is expected about mid-November. Feeding
will contribute to build-up of sooty mold.
Other pests are expected to be at low to moderate levels and of little concern except
in very limited areas.
600 October 22, 1969 WAS
W. A. Simanton