Coleosporium inulae

EbrahimK, Walaa & BarbarK, Ziad, 2023, Mite fauna on Dittrichia species (Asteraceae) in Syrian costal region: new records and primary observations on the behavior of Typhloseiella isotricha (Athias-Henriot) (Meostigmata: Phytoseiidae), Acarologia 63 (2), pp. 529-538 : 535-536

Coleosporium inulae seems as eventual source of alimentation of T.

isotricha

Typhloseiella isotricha was observed on D. viscosa near or close to the opened spots of rust

( Figure 2 ). The highest density of this predator was observed on big leaves (mean ± SE mites per leaf: 2.13 ± 0.31) (Figure 3) having high density of rust spots (3.30 ± 0.24 spot per leaf).

It was significantly different from big leaves without rust spots (0.13 ± 0.06 mites/leaf) H (=

61.1; df = 1; P <0.001), but also from small leaves with low density of rust spots (0.13 ± 0.07)

(0.08 ± 0.04 mites/leaf) (H = 57.8; df = 1; P <0.001). No significant differences were recorded between small leaves with rust and big leaves without rust H (= 3.5; df = 1; P <1.00).

The distribution of T. isotricha on different groups of D. viscosa leaves follows a negative binomial distribution and very similar to this of rust spots (Figure 4). The value of the index of aggregation (I = 2.9; S 2 = 2.226 and m = 0.77) is> 1, and the k exponent of the negative binomial distribution k (= 0.41) suggests a highly aggregate distribution. Moreover, the presence of rust spots on leaves of D. viscosa seems a significant predictor of the number of T. isotricha on this plant. Actually, the coefficient estimate “B” = 0.752, SE = 0.01, P <0.001 and the incidence rate ratio, Exp (B) = 2.12, indicates that for every one unit increase on the predictor (rust spots),

the number of T. isotricha increases by a percent of 21.2%.

These results seem to show that T. isotricha prefers big leaves of D. viscosa that are highly infested by the rust spots of C. inulae . These results suggest that rust spores could be a potential food source for T. isotricha . The presence of all developmental stages of this predator on leaves infected by the rust and, the absence of other sources of feeding such as phytophagous mites on examined leaves would indicate that the predator could feed, survive, develop and probably reproduce on rust spores. As already reported, several phytoseiid species have the ability to feed on fungi: Typhlodromus pyri Scheuten and Amblyseius andersoni (Chant) , for example,

could survive, develop and oviposit on grape downy mildew Plasmopara viticola (Berk. &

Curtis) Berlese & De Toni ( Pozzebon and Duso, 2008) and Ricoseius loxocheles (De Leon)

can feed and develop successfully when feeding exclusively on coffee rust Hemileia vastatrix

Berk. & Broome ( Oliveira, 2012). Therefore, experiments under laboratory conditions should be carried out in order to clarify the biology and to test the predation ability and feeding habits of T. isotricha on different preys and sources of alimentation.

Figures

Figure 2 Typhloseiella isotrichaspecimens close to rust spots of C. inulae infested leaves ofD. viscosa (scale bar = 1mm)