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CES kMimeo Series 69-3
CITRUS EXPERIMENT STATION
3 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 APRIL THROUGH JUNE 1968
Two mites and two scales were abnormally abundant during the period, but several
other citrus pests were unusually scarce. Citrus rust mite was the pest of most concern
because population continued to be above normal and in the high range throughout the
period. Between 63 and 74% of groves were infested and 41 to 53% of groves had moderate
or heavy infestations. The high population changed very little despite an extremely dry
April (less than 1 inch of rain) and an extremely wet June (about 20 inches of rain).
In April, Texas citrus mite increased sharply to above average but moderate level. During
June, the rate of increase diminished and population did not exceed the high level normal
for the end of June. Citrus red mite held to normal low levels until mid-May. June popu-
lation was the lowest for June in 17 years of record and did not enter the high range.
Heavy infestations occurred in only 12% of groves. Six-spotted mite remained below normal
and unimportant throughout the period. Only 6% of groves harbored this pest.
Scale insects generally were delayed 3 to 4 weeks in starting the spring buildup due
to the persistent cool temperatures prior to April. Black scale increased rapidly from a
very low level at mid-May to a record high level for June. In June, 93% of groves were
infested and 50% had heavy infestations. Snow scale was present in more groves (16%) than
in prior years but infestations were slightly lighter than in the same period of 1967.
Glover scale was the next most common scale, being present in 77 to 88% of groves during
the period. However, infestations were the lightest since 1963. Purple scale population
was the lowest for June in 17 years of record. Chaff scale and yellow scale, although
present in a majority of groves, continued at subnormal levels and were of little importance
Whiteflies were in normal moderate abundance.
Mealybugs increased rapidly to high level after mid-May but June population was
slightly lower than the average of recent years. Aphids were much below normal abundance
due to late appearance and rapid hardening of the spring flush.
GENERAL FORECAST JULY THROUGH SEPTEMBER 1968
Rust mite population is expected to be in the moderate to high range until mid-August,
which is about normal for the period. Decrease to low level will occur mid-August to mid-
September. Heavy infestations on fruit will occur in 15 to 20% of groves.
Texas citrus mite and citrus red mite will decrease in July and hold at low level
through September. Scattered infestations may become important in young groves.
Black scale will remain abnormally high through July and contribute to heavy buildup
of sooty mold. Adults will diminish in August but crawlers will become numerous. High
mortality of young scale is expected in September.
Snow scale is expected to spread and intensify.
Glover scale, purple, chaff and yellow scales are all expected to be at or below
normal abundance and to decrease through September.
Mealybug will persist in moderate numbers until August and contribute to sooty mold
buildup, then drop to low level.
Whiteflies will decrease through August; then increase in September. The larval form
will be present in moderate numbers throughout the period and add to the development of
625 July 16, 1968 WAS
W. A. Simanton