Granular Systemic Insecticides
By Charles F. Scheer Jr.
Cooperative Extension Agent (Nursery)
Cooperative Extension, Suffolk County, New York
Ornamental horticulturists grow a large variety of plant materials which may become infested with many different insects and mites that require different types of control measures. This complexity of hosts, insects, mites, insecticides, miticides and time and method of application has led horticulturists to search for better ways to control ornamental plant pests. Researchers have begun to investigate the use of granular systemic insecticides as soil applications. In a number of cases granular systemics applied to the soil and taken up by the plant will protect it for a much longer period than conventional foliar sprays. To date most of these granular systemic insecticides used have been highly toxic to man. Research is presently underway to produce more effective systemics which have lower mammalian toxicities.
This type of treatment can reduce the amount of environmental contamination and number of beneficial insects killed. Therefore, with the possible development of safer granular systemic insecticides in the future a new technique for insect and mite control may be possible.
Below is a report of research work done using the more toxic systemics to control aphids on newly rooted rhododendrons. This report points out some of the recent developments in this field. It must be noted that these systemic insecticides are presently registered for use by commercial growers only and are not recommended for use by anyone else.
APHID CONTROL ON NEWLY ROOTED RHODODENDRONS
On Long Island, New York, hybrid rhododendrons which are propagated from cuttings in late summer and early fall are generally grown in greenhouses after rooting to develop a better plant for spring planting. During this growing period these newly rooted rhododendrons can become repeatedly infested with aphids. Repeated foliar insecticide sprays have been necessary to control these aphid infestations. This study was designed to determine if granular systemic insecticides applied after the newly rooted rhododendrons are planted in the greenhouse benches would effectively control aphids until the plants were removed from the greenhouse.
Materials and Methods
Rooted cuttings of Rhododendron catawbiense (hybrid) varieties 'Roseum Elegans', 'Catawbiense Album', and Nova Zembla with the majority 'Roseum Elegans' were used in this experiment. The study was conducted in two greenhouses, one glass and one polyethylene. The experiment was replicated in each house with test plots containing 250-275 rooted cuttings. The rhododendrons were planted on October 15-17 in raised wooden benches in a medium of nearly equal parts German peat and coarse perlite.
Treatments using 10% granules of Di-Syston, Thimet and Temik were applied on January 4, 1968 using a randomized design. Di-Syston and Thimet were applied at 5, 10 and 20 lbs. toxicant per acre and Temik at 3, 6 and 12 lbs. All treatments and checks were replicated three times in each house except Temik treatments which were only replicated twice in the polyethylene house. Granulars were applied with a small hand duster and after treatment all plots were lightly watered. The plants were fertilized with 20-20-20 liquid fertilizer when necessary and pruned to develop better branching.
The rhododendrons were infested with aphids (Masonaphis azaleae Mason) on February 20, 1968 in the polyethylene house and on April 17, 1968 in the glass house.
Table 1 Control of aphids, Masonaphis azaleae (Mason) on rooted rhododendron cuttings in a polyethylene greenhouse, Huntineton, L.I. N.Y. Number of Aphids1 All 10%
Active Ingred. Per Acre
April 17, 1968 April 29, 1968 %
% Reduction Total2 From Check From Check Temik 12 4 99.6 1 * 99.9 6 6 99.4 6* 99.2 3 38 96.7 29* 96.6 DiSyston 20 2 99.8 3* 99.6 10 9 99.2 3* 99.6 5 51 95.5 46* 94.6 Thimet 20 72 93.7 180* 78.9 10 116 90.7 127* 85.1 5 226 80.1 330 61.2 Check 1133 850 1On 60 leaves, 20 leaves per plot. 2All treatments significant over check at 0.01 level by t test *Significant over check at 0.001 level by t test.
The total number of aphids were tallied on 20 young leaves taken randomly from the new growth of each plot. On April 17th the effects of the insecticides in the polyethylene house were apparent (Table I). By April 29th the effect of the Thimet treatments had weakened so that these plots could easily be picked out visually. By May 31st Thimet treatments at 5 lbs. toxicant per acre were little better than no treatment in the glass house. (See Table 2)
Table II Control of aphids, Masonaphis azaleae (Mason)
on rooted rhododendron cuttings in a glass greenhouse. Huntington, L. I., N.Y. May 31, 1968
All 10% Granular
Active Ingred. Per Acre
Number of Aphids1 Total % Reduction
Temik 12 1* 99.8 6 0* 100.0 3 0* 100.0 DiSyston 20 1 * 99.8 10 2* 99.6 5 33* 94.3 Thimet 20 56* 90.3 10 78* 86.5 5 558 3.3 Check 577 1On 60 leaves, 20 leaves per plot. *Significant over check at 0.001 level by t test.
These experiments indicate that DiSyston at 10-20 lbs. toxicant per acre or Temik at 3-12 lbs. toxicant per acre applied as 10% granular are effective in controlling aphids on rooted rhododendrons in 50-50 peat-perlite media from January to June under green house conditions including normal cultural pruning. The materials used in this experiment are highly toxic to man and chemical cartridge respirators which would absorb toxic organic vapors, rubber gloves and boots plus protective clothing should be worn when working with these materials.
Johnson, W. T., 1960, Studies with several systemic insecticides for control of azalea lace bugs, J. of Econ. Entomol., Vol. 53 (5): 839-841.
Schread, John C., 1968, Control of lace bugs on broad leaf evergreens, Bulletin No. 684, Conn. Agric. Experiment Station, New Haven, Conn.
Streu, H. T., 1966, Systemic control of mites and nematodes in azaleas, American Nurserymen, June 1, 1966.
Treece, R. E. & J. G. Matthysse, 1959, Use of systemic insecticides of woody ornamental plants, Bulletin 945, N. Y. S. College of Agriculture.