ENTOMOLOGICAL PROBLEMS SCALES
SCALES
When trees are
planted 264 to the acre, pest control
obviously becomes difficult. Even at greater
spacings, including the prevalent 7 X 7
meters, canopies soon join and make impossible the use of
machinery in the rows. Pesticides are
applied by station- ing sprayers at
the edges of the groves and by
"dragging garden-type hoses from the tanks to positions between the rows. Inadequate pressure and faulty coverage result in poor control; in addition, there is the custom
of using 1 percent medium oils, when what obviously is needed is a 2
percent oil.
Aonidiella
aurantii (Mask.) is the most prevalent scale. In recent years, it appears to have
crowded out the "black" scale, Chrysomphalus
aonidum (L.). Also present, but only
of moderate concern, is Ceroplastes sp.
Rust mite
Present practice
calls for the application of one sulfur dust annually to
prevent russet. Rust mites are present, the species being Phyllocoptruta Olievora Ashm. The whole
citrus-growing area is dusted between June and October. ..Control of russet is
obtained in variable degrees; about
10 percent of the fruits on the local
narket are russetted.
Applications of
sulfur are generally made with knapsack
dusters. Deposits are uneven; some leaves are
-so heavily coated that appreciable
quantites of sulfur persist for as long as half a
year, especially during the dry summer months. Heavy residues cause further troubles when oils are later applied on top of them. Much oil-sulfur burning of the fruit was in evidence, and one of the factors responsible for the many recently killed twigs and branches in some groves, as well as the prevailing thinness of the foliage, is probably the toxic interaction of these two
pesticides.
Zineb (zinc
ethylene bisdithiocar-bamate), a material
found in Florida to be exceedingly effective for
the control of russet (2), has not been used. This
material would provide better control of
russet and would not damage the
fruit and foliage as does oil and sulfur.
No comments:
Post a Comment