Sugarbeet Root Maggot Control-1971

Richard D. Frye, Associate Professor of Entomology
Albin W. Anderson, Research Associate in Entomology
John A. Callenbach, Professor of Entomology

Field investigations on the sugarbeet root maggot during 1971 were concerned primarily with control of the pest. The main test involved chemical insecticides, including cleared (approved labels) and uncleared materials. Other work involved 1) experimental insecticides, 2) effect of planting date and time of insecticide application on maggot control, 3) insecticide-herbicide compatibility, and 4) resistance of beets to maggot attack. All work was conducted in the St. Thomas area. The following results and comments are preliminary but should be of interest.

Main Insecticide Test

The test was conducted at three locations. The maggot infestation in each plot is shown in Figure 1. Although the infestations were somewhat uneven in all plots, there were sufficient numbers to provide good experimental data in all parts of each plot. Thirty-four treatments were replicated four times at each location. Each treatment was applied to four100 foot rows in every replication. Granular formulations were applied in seven inch bands over the rows, and incorporated with drag chains.Liquid formulations were also applied in seven inch bands over the rows.Pre-emergence applications were made shortly after planting. Post-emergence applications were made after early fly emergence was observed.

Results are presented in Table 1 and Table 2, and arc based on yields from two adjacent 15 feet of row in each replication of each treatment.

Most of the insecticides increased yields. Increases ranged from 0.4 tons per acre with granular Di-Syston applied pre-emergence at 1 lb. actual insecticide per acre to 4 tons per acre with granular Temik at 1 lb. per acre pre-emergence followed by 1 lb. post-emergence. There was a decrease of one ton per acre from the check with Dylox at 2 lbs. per acre applied as a bait. For practical purposes, the results indicate that several treatments gave good maggot control.

In terms of actual insecticide, approximate cost per pound of the insecticides in Table 2 are $1.51 for Thimet, $2.93 for Dasanit, $3.03 for Diazinon and $9.00 for Temik.

Effectiveness of materials under different seasonal weather conditions, cost and phytotoxicity are some of the factors growers must consider. These data are for 1971, a good year for beet growth and insecticidal applications; they may change in another year with loss optimal conditions. An additional consideration is the ability of insects to build up resistance to insecticides. The sugarbeet root maggot is a good example. Between 1955 and 1964 almost complete resistance to the chlorinated hydrocarbon insecticide aldrin was developed. In view of this, perhaps available insecticides should be alternated from year to year. For example, use a phosphate (such as Diazinon, Thimet or Dasanit) one year, and a carbamate (Temik) the next year. Such a practice might prevent, or at least delay, development of resistance in the maggot.

Experimental Insecticides

Table 3 records the results of a non-replicated test of experimental insecticides used against the maggot. The results are based on maggot counts.

The best results were obtained with M-3573, Dursban 10G, Dursban 1G, and AC64475. The use of granules with a lower concentration of Dursban (1percent) seemed to give better control (91 percent) than Dursban granules with a 10 percent concentration (70 percent) when used at the same rate. Note also that 2 lbs Dursban 1G gave control equal to 5 lbs Dursban 10G. This may be be due to the use of more granules of Dursban 1G, the lower concentration. More uniform coverage may be obtained when applying the less concentrated material with its greater bulk. Most of the experimentals gave some control when compared to the untreated check. However, there was no control with Dylox bait and Orthene, and very little with AC84484 and AC72841.

Effect of Planting and Insecticide Application Times on Root Maggot Control

Results of a replicated test to determine the effect of planting time (first planting May 19, second planting June 1) and time of insecticide application (pre-or post-emergence) on maggot control are given in Table 4. The data are based on maggot counts. Stands were too uneven to obtain yield data.

Overall, the best maggot control was obtained with the early beet planting combined with post-emergence application of insecticides.

Insecticide-Herbicide Compatibility

Results based on yields indicate that there were no antagonistic affects of herbicides on insecticides. Insecticides used in the test included Dyfonate (at 1 lb), Temik (at 1\ lbs), Thimet (at 1 lb) and Dasanit at 2 lbs actual per acre. TCA, Avadex, Eptam, Ro-Neet, and Eptam plus Avadex were the herbicides used. All possible combinations of the insecticides and herbicides were tested. The work was done in cooperation with Dr. Allan Dexter.

Comparisons of Sampling Methods Used to Evaluate Insecticide Treatments

Yields based on large and small samples of beets are compared in Table 5.

The comparisons show that the small samples gave yield estimates very similar to estimates from larger samples. There was a strong mathematical correlation between the two types of samples. This is evidence that small samples are as reliable an estimate of yield as larger samples.

Several methods of assessing maggot control were compared. Included were 1) the number of maggots on the beet, 2) the number of maggots on the beet plus those in the soil in the area six inches around the beet, 3) maggot damage on the beet, and 4) yield. The comparisons indicated that in 1971 all of the sampling methods were equally useful for evaluating the effectiveness of insecticides.

Resistance of Sugarbeets to the Sugarbeet Root Maggot

Three hundred and forty different beets from various sources were tested for maggot resistance in a non-replicated test. Most of the beets were discarded after the first Year (1971). Selections which were retained are to be compared in a replicated trial in 1972. These are shown in Table 6.

All of the beets in Table 6 showed very little maggot injury. Beet number 285595 (Poland) was interesting. It had form and size similar to commercial sugar types, and also a relatively high sugar content when checked with a field refractometer.


1971 Sugarbeet Research and Extension Reports. Volume 2, pages 73 - 76.


Red River Trade Corridor
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