Application of Pluronic gel to the study of root-knot nematode behaviour

Pluronic F-127 is a stable, non-toxic, copolymer that forms a gel at room temperature and a liquid at 15°C when the concentration is 20-30%. Root-knot nematode (Meloidogyne spp.) second-stage juveniles can move freely through the gel and display attraction toward roots of tomato, Medicago truncatula, common bean and Arabidopsis. The excellent clarity of the gel allows examination of behavioural changes in the nematode as it reaches and infects its host. Attraction assays showed that Meloidogyne javanica and M. incognita move to roots much more rapidly than does M. hapla. Nematodes form aggregates when in contact with root tips suggesting that the presence of a signal from the nematode or from the root is involved in the attraction. Nematodes suspended in Pluronic gel without roots aggregate into balls after 1 to 2 days. A coverslip placed on the gel accelerates and serves as a focus for the aggregation, suggesting that lower oxygen, or perhaps a volatile attractant, is involved in this behaviour. These observations demonstrate that Pluronic gel is a useful medium for dissecting attraction of root-knot nematodes to their hosts and for studying additional aspects of their behaviour.

Responses of Diabrotica speciosa to a semiochemical trap characteristics

Responses of Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) to a semiochemical trap characteristics were investigated in the field. The trap consisted of plastic bottles with several perforations (0.5 cm diameter and 2.0 cm distance each other) and containing Lagenaria vulgaris L. (Cucurbitaceae) powder as cucurbitacin (arrestant and phagostimulant) source (0.28%). In common bean fields, transparent green traps caught significantly more males and females beetles than yellow, transparent and white traps. Yellow traps caught significantly more females than white traps. Transparent green and yellow traps baited with the volatile attractant 1,4-dimethoxybenzene caught 4.08 and 2.72 times more beetles than unbaited, respectively. Higher number of beetles was caught by 2L bottle traps than 1, 0.5 and 0.25 mL. In corn fields, transparent green bottle traps caught significantly more beetles in Campo Mourão and similar captures were found in Londrina field.

Trap attributes influencing capture of Diabrotica speciosa (Coleoptera: Chrysomelidae) on common bean fields

Refinements in trap characteristics may improve ability to monitor and mass-trap beetles. Field assays were conducted in common bean fields to assess responses of Diabrotica speciosa (Germar) to some trap characteristics. Golden yellow plastic cups (750 mL) traps caught more D. speciosa females and males than did clear traps. Carrot slices in Petri dishes baited with Lagenaria vulagaris L. powder (cucurbitacin source - 0.28%) caught more beetles than did dishes with carrot alone. Dispensers for the floral volatile attractant 1,4-dimethoxybenze were also compared. Rubber septa dispenser attracted more beetles than did control (dental wicks saturated with acetone). Captures on dental wick, starch matrix and feminine pad dispensers were intermediate and did not differ from those on rubber septa and unbaited controls. Perforated bottle traps (2000 mL), when baited with the floral attractant, caught more beetles than did window bottle traps (both traps contained L. vulgaris powder) in most assessments done from two to ten days after trap placement in the field. Traps with the insecticide carbaryl captured more beetles than did traps without it, 2-4 and 8-10 days after trap placement in the field, but not in the remaining periods (0-2, 4-6 and 6-8 days). Traps baited with 1,4-dimethoxybenzene captured more beetles than did the unbaited ones in all assessments (each other day from two to ten days after trap placement in the field). Finally, similar amounts of beetles were captured using plastic bottle traps (2000 mL): perforated, window (both with cucurbitacin) and sticky (without cucurbitacin) traps, when were baited with the floral attractant.