Egg hatching of the soybean cyst nematode,Heterodera glycines, was not affected by millimolar concentrations of calcium sulfate or calcium chloride. However, zinc chloride and zinc sulfate caused strong and moderate increases in hatching, respectively. The inhibitors of calcium transport, ruthenium red and lanthanum chloride, and calcium ionophore A23187 had no effect on hatching in the presence or absence of 3 mM zinc chloride. Selected chelators decreased the zinc-induced hatching ofH. glycines eggs. Eggs exhibited a formation constant with zinc between 5.5 and 11.2. The addition of zinc chloride after chelation with EDTA and rinsing caused expected hatching rates. Concentrations of calcium chloride, manganese chloride, and magnesium chloride had no effect on hatching of eggs in zinc chloride, but reduced hatching at higher concentrations, possibly by osmotic influences. Hatching of eggs was increased as the time of exposure to zinc chloride was increased and was maximal at 28 °C and a pH of 5.3. Picrolonic acid, a known hatching stimulant, increasedH. glycines hatching, while sodium metavanadate had no effect. Analysis of seasonal hatching during 1981-1982 in untreated control eggs indicated that hatching was most pronounced in May.

Second-stage larvae of the soybean cyst nematodeHeterodera glycines Race 3 were attracted in an in vitro bioassay to pooled leachates of soybean roots that were expressed as root gram-hours (1 g of root/hr/vol). Their responses were dosage dependent with maximal attraction to a 5 root g-hr/ml source. Optimal bioassay conditions used 24 hr for gradient formation and 1.5 hr for larval movement. Individual plants produced leachate with little variation in biological activity. Production was constant for five days of preparation. The attractive activity of root leachate declined with storage at 4 °C and heating over 30 °C, but loss of activity was reduced by freezing. Extraction and Sep-Pak fractionation indicated that the attractions(s) was water-soluble. Larvae were attracted also to several ionic solutions.

The cuticle of Haemonchus contortus, Nippostrongylus brasiliensis and Trichostrongylus colubriformis contained N-acetylgalactosamine and N-acetylglucosamine, based on the binding of fluorescein-labelled lectins. Binding of the lectins varied between the sexes and body regions of the nematodes. Treatment of male T. colubriformis with the lectin Lens culinaris agglutinin (LcA) reduced the feeding by helminths that was stimulated by histamine and the male's response to their female's pheromone, based on in vitro assays. Mannose residues may be involved in the helminth's chemoreceptors for feeding and sexual attraction, based on the specific binding of LcA.

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A toxin from Bacillus thuringiensis kurstaki was lethal to eggs and first- and second-stage larvae of the ruminant nematode Trichostrongylus colubriformis. Sheathed and exsheathed third-stage larvae were also killed by the toxin. However, susceptibility of the ova to the toxin decreased after several hours of development. Heating at 65 C for 1 hr or freezing at 0 C for 3 mo did not affect stability of the toxin. Ovicidal activity of the toxin was not altered by treatment with 13 microbial or mammalian enzymes, but toxicity was reduced by the antibiotics streptomycin or penicillin G and the enzyme inhibitor L-1-tosylamide 2-phenylethylchloromethyl ketone. Cuprous, ferrous, and zinc chlorides also inhibited the ovicidal activity of the toxin. Increased osmolarity of the assay media or solubilization of the toxin from pH 3 to 11 had no effect on toxicity for eggs. The membrane agents sodium vanadate and 4,4'-diisothiocyano-2,2' disulfonic acid stilbene increased (9-fold) and decreased (333-fold) toxicity, respectively. N-acetylneuraminic acid was the only tested sugar that reduced the toxicity of B. t. kurstaki.