Study on weevil pests of oilseed rape at Keszthely, Hungary.

One of the most important pests of rape in early spring are weevils (Ceutorhynchus spp.). The aim of our studies was to identify the occurring weevil species and to study their emergence, swarming, mating and damage. Our observations were performed on an experimental plot at Keszthely (Hungary, Zala County) in early spring of four consecutive years. Following species were collected and identified: Ceutorhynchus pallidactylus MARSHAM, Ceutorhynchus obstrictus MARSHAM, Ceutorhynchus napi GYLLENHAL, Ceutorhynchus pleurostigma MARSHAM. The obvious dominance of C. pallidactylus and C. obstrictus was detected. Their frequency of occurrence was 88-90% among the identified adults. We found that C. obstrictus was the last species to settle. Complete developmental period was 68 +/- 7 days in case of C. pallidactylus and 70 +/- 7 days in case of C. obstrictus. Average number of eggs laid by one female was 176 +/- 23 in case of C. obstrictus and 21 +/- 6 in case of C. pallidactylus.

Making soil containing numerous eggs of WCR for greenhouse and laboratory experiments.

In the course of our work we often faced to the problem that WCR lays its eggs unevenly (Berger, 2008) so it is impossible to find soils under field circumstances which contains eggs in homogenous distribution and in large numbers. Owing to the inhomogeneous distribution and low number of eggs it is quite difficult to study the effectiveness of soil disinfectant and seed-dressing insecticides on larvae of WCR in pot experiments. Therefore, the aim of our studies was to gain soil samples with known quantity and distribution of eggs. According to our prevailing idea, numerous adults are placed into a relatively small place under ideal environmental conditions and a small quantity of soil is provided for them to lay eggs.

Quick scouting of eggs of western corn rootworm (Diabrotica virgifera virgifera LeConte, 1868) from soil.

Main method to control the American Corn Rootworm is crop rotation (Camprag et. al., 1994) but we don't know how to determine the possible number of larvae under fall so we cannot use autumn cereals to change the row of cultivated plants. The pest spends almost 10 months in soil in egg and larval state (Chiang, 1973). There are two methods for scouting Diabrotica eggs and larval instars from soil over the winter. One of the two most important methods is holding soil samples on fixed temperature (Fromm et al., 1999). This method takes more than one and a half month but its result is highly reliable. The conventional egg-washing technique takes fewer days to count the number of Diabrotica eggs in soil but it has lower effectiveness than the other one because the eggs in a sample cannot be counted correctly. Our results show that the effectiveness of egg washing with high concentrated salty water (NaCl) is high and the method is quick enough to help planning the crop rotation even under the autumn period (Takács et al., 2004).

Effective control method of larvae of Diabrotica virgifera virgifera Leconte.

Larvae of WCR are feeding on the roots of corn while plants fall down. The egg hatching is continuous and soil insecticides are not effective to kill larvae. Unfortunately the recent control methods while we incorporate disinfectors Into the soil under seeding are not able to give enough effect on larvae of WCR under the whole period of larval development. We use to saw corn in the middle of April but eggs hatching start in the middle of May. The effectiveness of insecticides takes about one month so they are not able to protect plants from larvae are feeding on roots (Luckman et al., 1974 and Luckmann et al., 1975). They cause yield losses or in case of plant fall we can not harvest the corn. We have tested a material in greenhouse screening and field trips that is able to absorb insecticides and bind them into its body. This material is able to emit the agents continuously under the vegetation and we can protect our plants against the damages of WCR larvae. Our results shows that the material is able to elongate the effectiveness of the pesticides over 60 days and able to push the number of larvae under the economical threshold.

The ecological study of cotton bollworm (Helicoverpa rmigera Hubner 1808) in Hungary.

The cotton bollworm (Helicoverpa armigera Hbn.) is a poliphagous pest. Caterpillars feed on flowers, crops and seeds. In 2001 the meaningful catching-period was in August (Szeoke, 2001). In 2003 we detected the swarming already in June. We observed many caterpillars on its nutritive crops. It caused significant economic damage in this year. 1ST EXAMINATION: We collected larvae and reared pupae out of it in a pot. We took it into the soil. The swarming of the moths from the pots was in June. The mortality was high, more than 90%. 2ND EXAMINATION: We made cold tests with pupae. We examined 5 x 10 pupae in three treatments. In the first treatment we reduced the temperature to -2 degrees C for 4 weeks. 92% of the pupae survived this cold. In the second treatment we reduced the temperature to -2 degrees C for 3 weeks and to -7 degrees C for 1 week. 86% of the pupae survived this procedure. In the third treatment we reduced the temperature to -2 degreesbC for 3 weeks and -15 degrees C for 1 week. 100% of the pupae were perished. 3RD EXAMINATION: In the first treatment we raised caterpillars on 13 hours lighting and 24 degrees C. The swarming was from 20th April to 4th May 2004. In the second treatment we reared the worms on 20 hours lighting and 18 degrees C. The main swarming was on 3rd January 2004. So we could say that the cotton bollworm has diapause. The more effective factor of the diapause is the length of the lighting.

Colorado potato beetle larvae on potato plants expressing a locust proteinase inhibitor.

The natural defence system of plants often involves inhibitors of digestive enzymes of their pests. Modem and environmental-friendly methods try to increase this plant resistance by expressing heterologous protease inhibitors in crops. Here we report the effects of expressing a gene from desert locust (Schistocerca gregaria) encoding two serine protease inhibitors in potato on Colorado potato beetle (Leptinotarsa decemlineata) larvae. The gene encoding both peptides on a single chain was used for Agrobacterium-mediated transformation of potato plants. The presence of the active inhibitor protein in the leaves was verified. The feeding bioassays in the laboratory showed that despite the low level of the peptide in leaves, CPB larvae on transgenic plants have grown slightly but significantly more slowly than those on control potato plants. The results support the notion that expression of multifunctional proteinase inhibitors of insect origin in plants might be a good strategy to improve insect resistance.