Heliothis Larvae Research Articles

Populations of Arthropod Predators and Heliothis Spp. After Applications of Systemic Insecticides to Cotton123

populations of arthropod predators, certain groups of hymenopterous insects, and Heliothis spp. including the bollworm, Heliothis zea (Boddie), and the tobacco budworm, Heliothis virescens (F.), were sampled in experiments following in-furrow applications of disulfoton and Temik®, a 10% formulation of UC-21149 (2-methyl-2-(methylthio)propionaldehyde O-(methylcarbamoyl)oxime); sidedress soil applications of phorate, American Cyanamid CL-47031 (cyclic ethylene (diethoxyphosphinyl)dithioimidocarbonate), and Temik; stem applications of Azodrin® (3-hydroxy-N-methyl-cis-crotonamide dimethyl phosphate) and CL-47031; and foliar applications of toxaphene plus DDT. Results indicated that populations of certain predators, particularly those belonging to the order Hemiptera, may be reduced by applications of systemic insecticides. Spiders (order Araneida and certain groups of hymenopterous insects (families Braconidae and lchneumonidae) Were less affected. In 2 experiments, the number of eggs and larvae of Heliothis spp. increased as the population of predators decreased. These results demonstrated the importance of natural populations of predators in regulating populations of Heliothis spp.

Metabolic Fate of Carbaryl-Naphthyl-C14 in Boll Weevils and Bollworms1

Adult boll weevils. Anthonomus grandis Boheman, were treated topically and bollworm, Heliothis zea (Boddie), larvae and adults were treated by injection with carbarylnaphthyl-C14 Hydrolytic as well as oxidative mechanisms were involved in the degradation of the carbamate in both species. Chloroform-extractable metabolites tentatively identified were: 1-naphthol; 1-hydroxy-5, 6-dihydro-5, 6-dihydroxynaphthalene; 5, 6-dihydro-5, 6-dihydroxy-lnaphthyl N -methylcarbamate; and 1-naphthyl N -hyclroxymethyl carbamate. Unknown metabolites of a water-soluble nature were predominant in both insect species.

Comparative Seasonal Abundance of Heliothis Larvae in Cottonfields in Texas and Arkansas During Summer 19641

The seasonal incidence of larvae of the bollworm, Heliothis zea (Boddie), and the tobacco budworm, H. virescens (F.), in the test fields at Weslaco, Texas, and Little Rock. Arkansas, were similar as both had 2 distinct generations and only the bollworm increased in numbers sufficient to cause yield losses of cotton. The largest numbers of both the bollworm and the tobacco budworm larvae occurred during the same periods of the cotton-growing season. Significant yield increases of cotton over the control were gained from use of Matacil® (4-(dimethylamino)- m -tolyl methylcarbamate), carbaryl, GUTHION M-E® (1:1 mixture of azinphosmethyl and azinphosethyl) plus methyl parathion, and Co-thion® (mixture of GUTHION M-E and parathion), when applied on a 5-day treatment schedule.

Seasonal Distribution of Heliothis virescens and H. zea on Tobacco in Kentucky1

In Kentucky tobacco fields the number of tobacco budworms, Heliothis virescens (F.), relative to the proportion of corn earworms, H. zea (Boddie), appears to have increased over the past decade, and H. virescens is no longer a relatively rare species. During June, July, and August 1965, H. virescens constituted 100% of the Heliothis population from tobacco for several samples in 2 widely separated regions of Kentucky. At the same time H. zea was abundant on sweet corn, indicating that corn silks are strongly preferred over tobacco by the moths of H. zea for ovipositional sites. Two population peaks of Heliothis eggs and larvae were found on tobacco in 1965: one in mid-August and the other in late September. Tobacco suckers in September and October may be a major food source for an over-wintering generation of these 2 species.

Aircraft applications of insecticides in East Africa. XV.--Very-low-volume treatment of a seed-bean crop with DDT in oil solution.

Experiments are described on the aerial application of very low volumes (0·5 gal./acre) of oil solutions of DDT to control two pests, Heliothis armigera (Hb.) (bollworm) and Acanthomia horrida (Germ.) (brown bug), of the seed-bean crop in northern Tanzania. The method was compared with an improved variant of the standard commercial method of aerial control, in which DDT emulsion is applied at 1·85 gal./acre. This improved variant was also compared with a standard commercial treatment. Very-low-volume (solution) treatments were made with rotary atomisers, normal volume (emulsion) treatments with boom-and-nozzle equipment. The results were assessed, by measuring the amount of DDT deposited on filter papers and on the leaves of the crop and by estimating pest mortality from counts made immediately before and 48 hours after spraying.A direct comparison of very-low- and normal-volume treatments under identical conditions was not possible, but it was established that under similar conditions the proportion of DDT emitted that was deposited at crop level (percentage recovery) was much the same for the two methods, varying between 41 and 62 per cent, according to conditions. The lower leaves of a fairly young crop of an open variety received about 60 per cent, of the deposit on the upper leaves, but in a mature crop of a tall dense variety this percentage fell to 35.Standard commercial practice, with the aircraft flying very close to the crop, gave a recovery of about 55 per cent, in moderately good conditions but with a variation in deposit density across the swath of over 7:1. An identical application from 10 ft. above crop, as in our method gave in rather better conditions a recovery of 62 per cent., with the deposit-density variation reduced to 2:1. This performance was much the same as that achieved by the type of emulsion application used in the other experiments described.In similar conditions, both very-low and normal-volume treatments gave very similar mortalities of Heliothis. Acanthomia was present in only one experiment and was less readily controlled; it required deposits at crop level of about 0·4 lb./acre to give satisfactory mortality, whereas in the same experiment 0·25 lb./acre gave 96 per cent, mortality in a relatively young Heliothis population containing only 10 per cent, of sixth-instar larvae.Older Heliothis larvae required higher dosages, 0·4 lb./acre at crop level killing only 53 per cent, of a population containing 62 per cent, of sixth-instar larvae. It was shown that there is a regular decrease in the kill inflicted by a given dosage on the successively later instars (from 92 per cent, of the third to 66 per cent, of the sixth) with a recorded deposit of 0·63 lb. DDT per acre.Except in the first experiment, mortalities were much below those claimed for commercial treatments, even at lower rates of DDT per acre. The reasons for this are discussed, together with the advantages to be expected from a change to the very-low-volume technique with solutions.

Seasonal Occurrence of Heliothis Larvae on Cotton in Louisiana2

The bollworm, Heliothis zea (Boddie), and the tobacco budworm, Heliothis virescens (F.), are becoming increasingly important as cotton pests in Louisiana. Resistance to DDT in H. zea was first detected during 1958 (Graves et al. 1963) and now occurs in all the major cotton-producing areas of the State. However, H. virescens collected from the same fields where H. zea exhibited high levels of resistance to DDT showed no signs of having developed resistance to any of the insecticides used for cotton-insect control (Graves et al. 1964). As a result, the need arose for a thorough evaluation of the relative numbers of the 2 species on cotton throughout the growing season.

Estimates of the Numbers of Heliothis Larvae Per Acre in Cotton and Their Relation to the Fruiting Cycle and Yield of the Host

Populations of Heliothis larvae composed of the bollworm, H . zea (Boddie), and the tobacco budworm, H . virescens (F.), were studied in small field plots undergoing treatment with various insecticides. The occurrence of larval populations broadly paralleled that of the flowering cycle of the host. Greatest numbers of the insects were present during the period when the plants had the greatest numbers of flowers. As the cotton approached maturity and bolls began to open and terminals and squares to abort, the larval population declined drastically. There appeared to be little relationship between the numbers of eggs deposited in the cotton fields and the subsequent numbers of larvae that survived. It was estimated from the results of this study that an average of 2000 to 2500 larvae (or approximately 1.5 to 2.0 per 10 ft of row) per acre are required to cause significant yield losses to cotton.

Wild Host Plants of the Corn Earworm and the Tobacco Budworm in Eastern North Carolina1

Surveys were conducted to determine the species of wild plants utilized as hosts by the corn earworm (Heliothis zea (Boddie)) and the tobacco budworm (Heliothis virescens (Fabricius)) in eastern North Carolina. In addition, an estimate was made of the abundance of several of these hosts. the abundance of Heliothis larvae on these plants, and mortality factors operating in these communities were investigated Corn earworm and tobacco budworm larvae were collected from 10 species of wild plants. The vast majority were found associated with toad flax (Linaria canadensis var. texana(Steeled) Pennell) and several species of deergrass (Rhexia mariana Linnaeus, Rhexia alifanus Walter, and Rhexia nashii Small). Toadflax serves as an early-season host for both the corn earworm and the tobacco budworm. while the tobacco budworm also occurs on deergrass later in the seasoil The parasites, Campoletis perdistinctus (Viereck) and Netelia sp., were reared from corn earworm larvae associated with toad flax. Cardiochiles nigricep8 Viereck parasitizes tobacco budworm larvae feeding upon deergrass.