APRIL 1982 IN INsecticides Applied at Planting Time or as Foliar Sprays to Control Chinch Bugs on Grain Sorghum

In recent years large areas of the sorghum crop in central and eastern Kansas have been damaged repeatedly by chinch bugs. The outbreak was more severe than at any time since the 1930's and overwintering numbers (as counted in the spring of 1981) were higher than at any time in recorded history. Research has been underway since the mid-1970's to identify ways of preventing or reducing damage. One approach has been to apply systemic insecticides to sorghum or corn at planting time to provide protection to the emerging seedl ing. The most promising method in that approach has been to apply granular carbofuran (Furadan) infurrow. With adequate soil moisture, it has protected the seedling plants about 3 weeks. Another approach has been to use rescue treatments by applying insecticides as foliar sprays directed toward the base of the plants where the bugs are congregated. In previous studies we have obtained an excellent degree of knockdown with carba-ryl (Sevin) or carbofuran (Furadan) applied in this manner. Observations and data do indicate, however, that most foliar applied insecticides have a relatively short period of residual performance and must be applied frequently under conditions of reinfestation. In 1981 we continued our studies on both plantingtime and foliar treatments using both labeled and experimental nonlabeled compounds. Results for 1981 are presented here.

In recent years large areas of the sorghum crop in central and eastern Kansas have been damaged repeatedly by chinch bugs. The outbreak was more severe than at any time since the 1930's and overwintering numbers (as counted in the spring of 1981) were higher than at any time in recorded history. Research has been underway since the mid-1970's to identify ways of preventing or reducing damage. One approach has been to apply systemic insecticides to sorghum or corn at planting time to provide protection to the emerging seedl ing. The most promising method in that approach has been to apply granular carbofuran (Furadan) infurrow. With adequate soil moisture, it has protected the seedling plants about 3 weeks. Another approach has been to use rescue treatments by applying insecticides as foliar sprays directed toward the base of the plants where the bugs are congregated. In previous studies we have obtained an excellent degree of knockdown with carba-ryl (Sevin) or carbofuran (Furadan) applied in this manner. Observations and data do indicate, however, that most foliar applied insecticides have a relatively short period of residual performance and must be applied frequently under conditions of reinfestation.
In 1981 we continued our studies on both plantingtime and foliar treatments using both labeled and experimental nonlabeled compounds. Results for 1981 are presented here.

Results with the use o f planting time insecticides
In the first test on sorghum planted next to wheat on june 5, granular applications were applied at planting and evaluated at 11 a nd 18 days af terwards ( Table 1 ). The infurrow treatment of carbofu ran and Tattoo significantly reduced chinch bug numbers and increased plant survival. In the second test on sorghum planted June 17, granular and liquid formulations were evaluated at 10, 20 and 29 days after planting (

Results with foliar applied insecticides
In two tests involving grain sorghum at Manhattan in 1981, we evaluated vario us labeled and experimental nonlabeled compounds in foliar applications for chinch bug control. In these studies, t he initial k nockdown of chinch bugs was indicated in the counts that were made one day after treatment, and residual performance noted 4, 8, and 14 days after the treatment counts. All insect icides significant ly reduced chinch bug numbers, as counted one day aft er treatment. The degree of reduction, howeve-r, ranged from 99.7% w ith f envalorat e (Pydrin) to 19.3% with phorat e (Thimet 15G) in Test 1 (Table 3); and from 100% with FC R 1272 t o 26% with Aspon at-the 1 'il lb. per acre rate in Test 2 (Table 4). Of t he in· secticides labeled for chinch b ugs on sorghum in the first t est, Lorsban at the .7.5":1b. rate gave the best residual performance as judged at ·4, 8, and 14 days after treatment FCR 1272, an experi mental compound t hat also provided good i nitial and residual control, deserves further st udy. I n Test 2, a few treatment s showed residual activity on the 4th day but by the 14t h day, only Endrin, Lorsban at 0.75 lb. A l/acre, and FCR 1272 at 1.0 lb. AI/ acre were con· tinuing to p rovide some control,

Discussion
Our studies indicated that infurrow applications of liquid carbofuran are as effective as granular formu lations. The liquid m ight have a slight advantage under dry soil conditions; that difference, however, m ight not be enough t o warrant the additional hazard encou ntered in handl ing the liquid solu tions during the busy process of planting. The use of carbofuran as a liquid combined in a tank mix with a starter fertilizer, applied infurrow at planting time, appeared to offer some advantage in t erms This publication from Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information: http://www.ksre.ksu.edu.
of reduced injury to sorghum plants. The current Kansas 24(c) label, written so as to not prohibit it from being combined w ith starter fertilizer, allows Furadan 4F to be applied as a liquid infurrow treatment. But the user does that at his own risk, and a few growers have reported severe stand losses where Furadan 4F combined with certain starter fertil. izer mixtures had been used. Growers are advised to investigate that possibility closely with chem ical representatives and fertilizer dealers before elec ting to use this approach. The results of our foliar studies showed that carbaryl (Sevin), carbofuran (Furadan 4F), chlorpyrifos (Lorsban 4E), all of which are registered for controlling chinch bugs on sorghum, gave good initial control of chinch bugs under the conditions of these two studies, and showed that chlorpyrifos (Lorsban 4E) might have some advantage in residual performance in controlling infestations if a continuing migration into the field is expected. This publication from Kansas State University Agricultural Experiment Station and Cooperative Extension Service has been archived. Current information: http://www.ksre.ksu.edu.