CHEMOSTERILIZATION OF EUROPEAN CORN BORER' ADULTS WITH DIFLUBENZUR0N2·3

A. A. Faragalla,' E. C. Berry, 5

L. C. Lewis,5 and W. D. Guthrie 5

Abstrad: Hatchability of egg masses from moth pairs of Ostrinia nubilalis (Huhner) originating from larvae reared on a meridic diet treated with 7.8 and 15.6 ppm of diflubenzuron was less than was hatchability of egg masses from moths originating from larvae reared on untreated diets. Only one sex of a cross originating from larvae reared on treated diet was sufficient to cause los9 of hatchability. Rearing larvae on treated diet for only 1 d was 8S effective in reducing subsequent egg hatch from the resulting adults as was rearing IlUY'ae on treated diet for 3, 5, 7. 9, or 11 d.

Key Words: European corn borer, Ostrinia nubilalis, chemosterilization, dillubenzufon

J. Agric. Entomol. 1(4), 371·375 (Oclobe, 1984)

European corn borer (ECB). Ostrinia nubiJalis (Hubner). is a major pest of corn, Zea mays (Linnaeus), and applications of conventional insecticides remain the primary defense for preventing economic damage. Insecticides are applied either for systemic activity at planting time (Edwards and Berry 1972) or as foliar treatments (Berry et aI. 1972; Harding et aI. 1968). Either technique is designed, however, to suppress the larval stage of the ECB. Investigations have shown, however, that female and male ECB can be sterilized by rearing larvae on diet treated with tepa and apholate (Harding 1967) or by dipping adults in an aqueous solution of metepa (Jackson and Brindley 1971).

Diflubenzuron is regarded as an insect growth regulator because it interferes with cuticle deposition in immature insects (Mulder and Gijswijt 1973). It has also been used as a chemosterlizing agent for some insects (Elings and Dieperink 1974; Ivie and Wright 1978; Mitlin et aJ. 1977; Moore and Taft 1975; Moore et al. 1978; Oliver et al. 1977; Taft and Hopkins 1975; Verloop and Ferrell 1977). We, therefore, designed an experiment to determine if dinubenzuron has a chemo· sterilizing effect on the ECB.

MATERIALS AND METHODS

Our experimental design was a split-split plot with concentrations of dilluhenzuron 85 the whole plot, number of days the larvae were allowed to feed on treated or nontreated diet prior to being transferred as the subplot, and moth crosses as the sub·subplot. Each treatment. was replicated fOUf t.imes.

We used 7.8 and 15.6 ppm as our concentrations of diflubenzuron. In exploratory experiments we showed rate responses between 7.8 and 15.6 ppm of

I LEPrDOPTERA: P)'Talidal' 2 Joint contribution: United Statu Department of Al:Ticulture, Agricultural Reaearch Service. and Journal Paper No.

J·9641 of the lown Agriculture end Home EconornicH Elperiment Stlltion, Amea 50011: Project 26L3. Itecnived for publicntion 9 April L9S4; accepted 24 .July 1984.

3 Mention of • propriolliry producl doct not constilute an endOl1lemenl by the USDA or coopernting llgenciu. " I'reannl nddresH: College of Agriculture, RiYlll! Unh·crHity. Riynd, Saudi Arabia 6 Com InaecU! Re~an::h Unit, USDA·ARS. Ankeny. lA SQO:l1.

371

372 J. Aerie. Entomol. Vol. 1, No.4 (1984)

diflubenzuron as measured by viability of eggs aud the production of othen'lise normal moths. ECB diet was prepared as described by Lewis and Lynch (1969). The two concentrations of diflubenzuron were prepared in the laboratory by methods described by Harding and Dyar (l970). ECB diet was topically treated by adding 0.2 ml of the 7.8 or 15.6 ppm concentrations of diflubenzuron to ca. 5 m1 of diet in 30 ml jelly cups. 'We introduced neonate larvae into a group of cups (one larva/cup) that had previously been treated with one of the concentrations of diflubenzuron. On day I, 3, 5, 7, or 11, 50 larvae from each concentration were transferred to untreated diet with a small brush and allowed to develop to pupation. Also, reciprocal transfers were made, i.e., larvae were transferred on day 1, 3, 5, 7, or 11 from untreated to dinubenzuron treated cups. Larvae used as controls were transferred from untreated to untreated diet.

As soon as the larvae pupated, the pupae were placed in individual jelly cups. Moths originating from larvae reared on untreated diet (U1j were crossed and identified as cross 1 = UT female X UT male. Moths originating from larvae reared on diflubenzuron treated (1') diet and then transferred to untreated diet were identified as T-UT. The following crosses were made and identified as follows: cross 2 = T-UT female X T-UT male, cross 3 = T-UT female X UT male, and cross 4 = T·UT male X UT female.

Moths originating [Tom larvae reared on an untreated diet and then transferred to diDubenzuron treated diet were identified 8S UT-T. The following crosses were made and identified 8S follows: cross 5 = UT·T female X UT-T male, cross 6 = UT-T female X UT male and cross 7 = UT-T male X UT female.

Approximately 20 pairs of moths of each of the crosses were placed in small cages (one pair/cage). These mating cages were screen-\vire cylinders, ca. 8-cm in height and 8-cm in Diam, with screen-wire bottoms and hardware-cloth tops (4 mesh). Waxed paper was placed on top of each cage for oviposition. The waxed paper was changed each day. The larvae were reared and the egg masses were incubated at 27°C, 75 - 90% RH, and constant light

Viability of ECB egg masses was determined a week later. A rating scale similar to that reported by Lewis et a1 (1971) was used where 1 = egg masses with 0% hatch, 2 = egg masses \vith 1 - 50% hatch, 3 = egg masses with 51 - 99% hatch, 4 = egg masses with 100% hatch, 5 = % egg masses that embryonated (blackhead stage) without hatching, and 6 = % egg masses that were sterile (no visual indication of larval development).

Means were used for analysis of variance. The total sums of squares for percent.age of egg masses with 0% hatch, percentage of egg masses \vith 100% hatch, percentage of egg masses which embryonated without hatching, and percentage of egg masses which were sterile were each partitioned into components for replications (3 dJ.), concentrations of diflubenzuron (1 d.f.), error a (3 d.f.), number of days the larvae were allowed to feed on treated or nontreated diet prior to being transferred (5 d.f.). days X concentration (5 d.f.). error h (30 d.f.), moth crosses (6 d.f.), crosses X concentrations (6 dJ.), crosses X days (30 d.f.), crosses X concentrations X days (30 dJ.l, and error c (216 dJ.).

RESULTS AND DISCUSSION

There was no significant difference in viability of eggs produced by moths reared from larvae treated with 7.8 or 15.6 ppm of diflubenzuron. Therefore, the

X

FARAGALLA et a1.: Chemosterilization of European Corn Borer 373

data in Table 1 were averaged over the two concentrations of diflubenzuron. The time interval that larvae were allowed to feed on dinubenzuron-treated diet and

Table 1. Influence of dinubenzuron on F 1 European corn borer eggs (summed over concentration).

Moth crosst

Larval age- l 2 3 4 5 6 7

Percentage of egg masses with 0% hatch 1 0.0 15.3 31.3 15.3 23.0 22.6 16.0 20.6 3 0.0 21.6 25.5 11.5 17.8 23.5 16.4 19.4 5 0.0 26.9 18.8 14.1 14.8 19.5 18.9 18.8 7 0.0 13.0 14.9 25.5 17.6 24.6 15.5 18.5 9 0.0 21.3 19.6 21.5 21.5 23.9 16.1 20.7

11 0.0 15.3 19.8 25.3 11.8 26.1 19.6 19.7 X 0.0 18.9 21.7 18.9 17.8 23.4 17.1

Percentage of egg masses with 100% hatch 1 77.5 8.6 5.4 13.0 17.1 18.1 19.6 13.6 3 88.5 13.2 5.4 19.4 15.3 19.5 26.8 16.6 5 89.3 18.0 12.5 27.9 31.4 23.4 31.5 24.1 7 93.8 7.0 21.1 21.6 24.5 15.8 20.4 18.4 9 79.3 8.8 19.3 13.3 11.4 13.0 13.1 13.2

11 84.5 23.0 11.5 23.4 23.0 24.4 21.9 21.2 X 85.5 13.1 12.5 19.8 20.5 19.0 22.2

Percentage of egg masses which embryonated without hatching I 0.0 12.8 20.5 13.8 14.3 12.1 7.0 11.5 3 0.0 18.5 13.8 24.0 12.4 14.0 6.8 12.8 5 0.0 17.4 10.9 15.1 8.8 13.6 10.6 10.9 7 0.0 19.3 10.4 9.4 11.6 20.1 10.0 11.5 9 0.0 5.9 16.9 16.5 15.6 17.3 11.4 11.9

11 0.0 14.9 11.3 7.0 11.3 17.5 13.5 10.8 X 0.0 14.8 14.0 14.3 12.3 15.8 9.9

Percentage of egg masses which. were sterile I 0.0 30.0 40.6 35.9 35.3 30.0 37.6 34.9 3 0.0 35.1 48.8 23.9 33.5 30.0 41.5 35.5 5 0.0 25.6 33.4 20.5 29.6 27.6 23.4 26.7 7 0.0 39.9 33.9 32.6 22.8 32.6 34.9 32.8 9 0.0 52.4 41.5 31.4 33.0 35.9 43.9 39.7

11 0.0 36.8 43.4 26.5 31.5 21.6 29.6 31.6 X 0.0 36.6 40.3 28.5 31.0 29.6 35.2

• Aile of larvue (d) when transferred (rom trealed diet to untreated diet or (rom unlreated diet to treoted diel t I - untreated (liT) female X untreated (UT) male

2 - treated (T)·untrellted (trI1 female X treated rI)-unlreated (UT) mAle 3 - T-UT femole X tiT molt> 4 - T-UT mnle X UT femole 5 - tiT·T (emilie X tiT·T mAle 6 - tiT-T femAle X til' mule 7 - ti'l'·T mule X UT (emole.

374 J. Agric. Entomol. VoL 1, No.4 (1984)

the order in which they were transferred, either from diflubenzuron·treated diet to untreated diet or from untreated diet to treated diet, was significant (P = 0.05) only in the 100% hatch and sterile categories. The order in which the moths were crossed was significant for percentage of egg masses with 0% hatch, 100% hatch, percentage of egg masses which embryonated without hatching, and percentage of egg masses which were sterile categories. Significant interactions between larval age X moth pair occurred only in the categories of 0% egg hatch, 100% egg mass hatch, percent egg masses which embryonated without hatching, and percentage of egg masses which were sterile.

A summary of the influence of diflubenzuron on ECB F 1 egg masses is presented in Table 1. Although the larval age X moth cross interaction was significant for all categories, the data suggest these interactions were due primarily to the magnitude of response between the untreated female X untreated male cross as compared to the other crosses (2, 3, 4, 5, 6, and 7). Production of viable egg masses was reduced regardless of the length of time larvae were allowed to feed on the diflubenzuron-treated diet. Rearing larvae on treated diet for 1 d was as effective in reducing the percen~ge of nonviable egg masses as was rearing larvae on treated diet for 3, 5, 7, or 11 d.

Production of viable egg masses was independent of moth crosses. In cross 2, both male and female moths were from larvae that were fed treated diet; however, production of viable eggs was similar to crosses 3 and 5 (females from treated larvae) and crosses 4 and 7 (males from treated larvae).

The 1 - 50% and 51 - 99% hatch categories are not given in Table 1 because the time interval that larvae were allowed to feed on ditlubenzuron-treated diet and the order in which they were transferred, either from diflubenzuron-treated diet to untreated diet or from untreated diet to treated diet and the order in which the moths were crossed were not significant (P = 0.05).

The results show that diflubenzuron is an effective chemosterilant of the ECB. These results, along with those of Faragalla et al. (1980), and Berry et al. (1980), demonstrate that diflubenzuron functions as a chemosterillant, ovicide, and larvicide against the ECB.

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375 FARAGALLA et aL: Chemosterilization of European Corn Borer

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