Occurrence of powdery mildew disease of Gerbera in Kerala

A purposive sampling survey on the hilly tracts of Wayanad, Kerala revealed the existence ofpowdery mildew disease in gerbera crops, grown under both protected and open field condition.Among the other fungal diseases of gerbera, powdery mildew disease causes decisive damageto the ornamental cut flower crop, thereby decline in the industrial value of the crop. Symptomof the disease include as white powdery mat on the upper surface of leaf lamina that graduallyturned pale yellow to brown. Powdery mildew existed in two locations of Wayanad viz.,Ambalavayal and Chulliyode where highest per cent disease severity (PDS) of 50.72 wasobserved at Chulliyode and 47.2 per cent was observed at Ambalavayal during November-December. In Ambalavayal, the disease was non-significant and no correlation existed betweenweather parameters and disease progress. But, in Chulliyode, correlation studies revealed thatit was significant with positive correlation to relative humidity and a reverse relation existedwith temperature and rainfall. The weather data clearly depicts that at a low rainfall of 96 mmand above average relative humidity of 80.27 per cent during November-December was thecongenial factor influencing the disease development. But during summer, decline in relativehumidity (78.37%) and rainfall (63.13 mm) caused a slight reduction in mean per cent diseaseseverity of 49.12 per cent and 33.6 per cent at Chulliyode and Ambalavayal respectively.Morohological and cultural characters of the pathogen depicts presence of two distinct organismviz., Golovinomyces cichoracearum (Erysiphe cichoracearum) and Podosphaera sp. as thecausative organism of the disease. Golovinomyces cichoracearumproduced hyaline, septatemycelia with globose conidia with irregular peripheral end formed in a chain and Podosphaerasp. produced superficial, hyaline, coenocytic mycelium with oval or ellipsoidal, catenate conidiawith dimension ranging from 22.1-30.18 x 13.36-18.08ìm formed in unbranched erectconidiophores.

Seasonal dynamics and life cycle of Heterotrissocladius marcidus (Diptera: Chironomidae) in high altitude lakes (High Tatra Mts, Slovakia)

We estimated the seasonal dynamics and life cycle of the chironomid Heterotrissocladius marcidus (Walker, 1856) in three alpine lakes in the High Tatra Mountains (Central Europe). H. marcidus had univoltine cycle in all lakes surveyed and seasonal changes of density showed an early summer and an autumn peak interrupted by a mid-summer decline of larval abundance. Our results indicate that phenology of H. marcidus is sensitive to thermal regime and local differences in lake water temperature can lead to differences of the life history within the same population

Response of birch (Betula pendula Roth) phytophages to liming

: In the course of 2004–2007, the effects of compensation liming at the application dose of 1.5–3–6 t/ha dolomitic limestone on the elimination or activation of phytophages or other types of damage resulting in the loss of assimilatory organs did not become evident yet. A shift was noted in the fluctuation expressed indirectly by the extent of damage to the assimilatory area in feeding caused by an undetermined hymenopterous larva (summer increase), weevils (spring and summer decline and increase in 2007), <I>Coleophora serratella</I> (decline), <I>Eriocrania</I> sp. (increase), mites <I>Acalitus rudis</I> (increase), <I>Eriophyes leionotus</I> (increase in 2006–2007). Only signs of a positive response to higher doses of dolomitic limestone characterized the mite <I>Eriophyes leionotus</I>.