Holdaway, F.G.

Proceedings of the Hawaiian Entomological Society

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421Differential Susceptibility of Varieties of Garden Bean toOviposition by Melon Fly, Dacus Cucurbitae Coq.1BY F. G. HOLDAWAYBack and Pemberton (1917) have recorded garden or "string"beans as a host of melon fly, although melon fly is not ordinarilyconsidered to be a pest of this crop. In the present paper evidenceis advanced which indicates that under certain conditions a comparatively high proportion of pods may be attacked and also thatthere is a marked differential susceptibility of varieties to attack.The first observations were made at Koko Head, Oahu, June 27,1938, where four varieties of bean—Tendergreen, Lualualei, Mc-Caslan, and Kentucky Wonder—were growing in close proximity.The first-named variety is a bush green-podded type, while theothers are pole beans of the same color class. Melon fly was themost serious pest of beans at that time and place, and pods of allvarieties were being attacked. For several months prior to the observations cucumbers and tomatoes (crops susceptible to melon-flyattack) had been grown in the vicinity and had been seriously attacked. By late June few cucumbers or tomatoes remained. However, the melon fly population had reached a high level, for largenumbers of adult flies took wing when plants in the plot of bushbeans were disturbed. The quantitative data on oviposition arenot as complete as might be desired but are placed on record becauseof the evidence they yield of varietal susceptibility of beans to melonfly attack,Pods in which oviposition has occurred exude a small amount ofgummy material at the point of oviposition. Records of attack wereobtained by counting the number of pods exhibiting this condition.These counts were made during the first week in July on two rows,each 100 feet long, of each of the pole varieties. The two rows constituted the total planting of McCasland and Kentucky Wonder.There was a larger planting of Lualualei; the two rows used forthese records were the two growing next to the Kentucky Wonder.No records were obtainable from the variety Tendergreen, sincepicking had ceased; according to the grower this variety had beenmore heavily attacked than any one of the other three varieties.The data are presented in table 1.The percentage of pods exhibiting oviposition by melon fly washighest in the variety Lualualei, next in McCaslan, and lowest inKentucky Wonder. Lualualei is a heavy, comparatively tardy cropper, and the period of harvesting is longer than in the other varie-i Published with the approval of the director as Technical Paper No. 70, HawaiiAgricultural Experiment Station.Proc. Haw. Ent. Soc, X, No. 3, August, 1940.422Table 1.Date ofpicking1938July 1July 3July 5July 1July 3July 5July 1July 3July 5Showing Differences in Susceptibility of Varieties of StringBeans to OvipositionVarietyMcCaslanttKentucky WonderLualualeiu((((Picking3rd4th5thTotal3rd4th5thTotal2nd3rd4thTotalby Melon FlyTotal number ofpods producedand examined11600(10 lbs.)720(12 lbs.)270 ( 4ilbs.)1590 (26i lbs.)650(13 lbs.)950(12 lbs.)350 ( 7 lbs.)1950(32 lbs.)2368(39* lbs.)2407 (39i lbs.)990(16ilbs.)5765 (95i lbs.)Pods showingevidence of oviposition bymelon flyPer cent3.56.59.65.90.90.92.01.15.69.613.58.7a The writer acknowledges the assistance of Mr. Adaniya, the grower of the cropin making the counts.ties. The exceptionally large pickings recorded above for thisvariety is thus probably accounted for, to some extent, by thesefacts. It is of interest to note that Lualualei is known to be highlysusceptible to bean rust in Hawaii, while certain strains of KentuckyWonder have been shown, by Dr. G. K. Parris of the Hawaii Experiment Station, to be much less susceptible.SUMMARYEvidence is advanced that "string" beans may be comparativelyheavily attacked by melon fly if the fly population is high and thereis a paucity of crops more attractive to the flies. Further, varietiesof string beans are shown to exhibit differential susceptibility tomelon fly attack. Of three varieties on which records were obtained,Lualualei exhibited the highest percentage of attack, McCaslan thenext, and Kentucky Wonder the lowest.REFERENCESBack, E. A., and Pemberton, C. E. 1917. The melon fly in Hawaii.U.S.D.A. Bui. No. 491, 64 pp.

Differential Susceptibility of Varieties of Garden Bean to Oviposition by Melon Fly, Dacus Curcubitae Coq.

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Differential Susceptibility of Varieties of Garden Bean to Oviposition by Melon Fly, Dacus Curcubitae Coq.

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