Earworms, corn

FIGURE 4 Proposed model for the interaction of PBAN with a receptor on the sex pheromone gland of a corn earworm female, and the resulting stimulation of acetyl-CoA carboxylase of the pheromone biosynthetic pathway. 

Cuts from the silica gel column were incorporated into artificial diets optimized for several economically-important agricultural pest insects, the pink bollworm Pectinophora gossypiella> the tobacco budworm Heliothis virescens> the corn earworm H. zea and the fall armyworm Spodoptera frugiperda. > Monitoring with this artificial diet bioassay, further column chromatography and preparative TLC on silica gel in diethylether-petrol yielded five... 

Zea mays Maysin (C-glycosyl flavone) Corn earworm, Helicoverpa zea 369... 

Byrne, P.F. et al.. Quantitative trait loci and metabolic pathways genetic control of the concentration of maysin, a corn earworm resistance factor, in maize silks, P. Natl Acad. Scl USA, 93, 8820, 1996. 

The development of natural resistance in corn (Zea mays) to the corn earworm (CEW) Helicoverpa zea) received many contributions. The CEW is a major insect pest of maize and other crops (cotton, soybeans, etc.) the eggs are laid on the silks, and the larvae access the ear by feeding through the silk channel. 

Snook, M.E. et al.. New flavones from corn Zea mays L.) silk including a novel biflavone that contribute resistance to the corn earworm Helicoverpa Zea (Boddie)), Abs. 222nd ACS Nat. Meeting, Chicago, 26, 2001. 

Figure 1.1 The three major types of hormones that regulate pheromone production in insects. A Juvenile Hormone III (C16 JH), B 20-Hydroxyecdysone and C PBANs from the corn earworm, Helicoverpa zea (Raina et al., 1989), the silkworm moth Bombyx mori (Kitamura et al., 1989) and the gypsy moth, Lymantira dispar (Master et al., 1994). The minimum sequence (pentapeptide) required for activity is indicated.

Kingan T. G., Bodnar W. M. and Hunt D. F. (1995) The loss of female sex pheromone after mating in the corn earworm moth Helicoverpa zea identification of a male pheromonostatic peptide. Proc. Nat. Acad. Sci. USA 92, 5082-5086. 

Unfortunately, Bt toxin doesn t work very well for the corn earworm making it difficult to control this pest on organic farms. Researchers continue to work on this problem, and hopefully a more effective organic solution will be found. I recently learned that injecting vegetable oil and Bt toxin into the silks of each ear with a special applicator was very effective and not overly time-consuming. I can t wait to try this technology (Diver et al. 2001). 

A number of insect species, including corn earworm, Heliothis zea (Boddie), and tobacco budworm, Heliothis virescens (F.), contain and C,g aldehydes (C al and C al) in their pheromone blends (22, 23). The release rate of a C. al would be expected to be higher than that of a Cj al because of the molecular weight difference. A mixture containing 10% n-tetradecanal (CjA°al) in Z)-ll-hexadecenal [(J0-Il-Cj al] was formulated in four laminates, each made from a different type of polymeric membrane as the top and bottom layers vinyl, Mylar -coated vinyl, acrylic, and rigid vinyl film. (The saturated C,.°ol was used as a model because of availability.) The total alaehyde content was approximately 2.3 mg per cnr of laminate 0.7% (of the pheromone weight) of 2,6-di-tert-butyl-4-methylphenol (BHT) was added as an antioxidant. Table II gives the thickness of the polymers. 

The object of the work described here was to measure the amount and distribution of pheromone vapor in the air under woodland canopies after aerial applications of slow release formulations of disparlure, and the rate at which these declined with time. A limited number of experiments have also been done Z-9-tetradecenol formate (TDF), a mating inhibitor for the corn earworm moth (Heliothis Zea). 

We observed that when adult females of the corn earworm moth (Heliothis zea) were ligated between the head and thorax so that normal hemolymph circulation between the brain and the rest of the body was interrupted, they did not produce sex pheromone. However, the ligated females could be stimulated to produce pheromone, in amounts not different from that produced by normal females, by an injection of a saline extract of the female brain. Our studies with this nocturnal moth indicate that the neurohormone is stored in the brain and released into the hemolymph in the scotophase causing timely production of pheromone by the female. 

Adding to the puzzlement of this system, we found that pheromone production could also be induced in the glands of ligated corn earworm females by injection of brain extracts of the male corn earworm and extracts of females from four different families of moths (Pyralidae, Lymantriidae, Geometridae, and Psychidae) (27). The sex pheromones of females representing these families have little or no chemical similarity to the corn earworm sex pheromone... 

Recent publications 0,4) in regard to the latter two plants indicate that they were also toxic to two bacteria which occur in the gut of the tobacco budworm Heliothis virescens (Fab.) and the corn earworm Heliothis zea (Boddie). The compounds, rhamnetin 3-0-glucoside and isoquercitrin, were isolated (3) from H camporum based upon their activity against Pseudomonas maltophilia and Enterobacter cloacae Also, a procyanidin was isolated (4) from Mj floribundum on the basis of activity against P. maltophilia. 

Ryania is made from the ground roots of the tropical shrub Ryania speciosa. The active principle of ryania is the alkaloid ryanodine (C25H35NOu). Ryania is used for controlling aphids, cabbage loopers, Colorado potato beetles, diamondback moths, cucumber beetles, leafhoppers, corn earworms, European corn borers, codling moths, citrus thrips, and so on. Its oral LD30 in rats is 1200 mg/kg so it is practically nontoxic to mammals. 

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