Influence of Abiotic Factors on Population of Aphid Complex and Its Coexisting Natural Enemies in Mustard Agroecosystem

A field experiment was conducted to determine the population build-up of mustard aphid and their natural enemies in relation to abiotic factors at TCA, Dholi during the Rabi season of 2018-19 and 2019-20 respectively. The incidence of mustard aphid started in the 2nd and 3rd SMW of 2019 and 2020 respectively and reached maximum in 8th SMW in both the years. However, the predatory activity of coccinellids, syrphid larvae and spiders were started from 3rd SW with their peak activity at 3rd and 4th week of February in both the years. Mustard aphid population exhibited positive correlation with maximum temperature (0.347 & 0.543), minimum temperature (0.317 & 0.152) and negative correlation with relative humidity (-0.083 & -0.479) during 2019 & 2020 respectively and rainfall (-0.35) during 2020. However, natural enemies viz., coccinellids, syrphid larvae and spiders exhibited positive correlation with Tmax, Tmin, rainfall and negative correlation with RH in both the years.

Identification of the Klambothrips myopori (Thysanoptera: Phlaeothripidae) Predator Complex in California

To identify the predator complex of the invasive thrips, Klambothrips myopori, on its ornamental host plant Myoporum laetum, field surveys were conducted at three sites in southern California over the period of 1 y. Five insect orders and five spider families were represented in the survey. Although the most abundant groups differed among collection sites, syrphid larvae, anthocorids, Chrysoperla spp., Franklinothrips orizabensis Johansen (Thysanoptera: Aeolothripidae), and one spider family (Salticidae) were all collected at each site. Based on the field surveys, Orius spp. and Chrysoperla spp. were identified as possible key natural enemies of K. myopori. Laboratory studies were then conducted to determine the consumption rates of Orius insidiosus Say (Hemiptera: Anthocoridae) and Chrysoperla rufilabris Burmeister (Neuroptera: Chrysopidae) at constant densities of K. myopori and to define the functional responses of the predators. Both predators consumed more second-instar larvae than other prey stages. Orius insidious displayed a type II functional response, while C. rufilabris displayed both type II and type III depending on prey stage. Generally speaking, O. insidiosus and C. rufilabris consumed a higher proportion of prey at lower pest densities, implying that in an augmentative control program using these commercially available natural enemies, predators could be released early in the year when host plants begin to flush and thrips populations are low to suppress population growth.

Syrphids (Diptera, Syrphidae) and coccinellids (Coleoptera, Coccinellidae) occurring in Myzus cerasi (F.) (Hemiptera) colonies on Prunus avium L.

Syrphids (Diptera, Syrphidae) and coccinellids (Coleoptera, Coccinellidae) occurring inMyzus cerasi(F.) (Hemiptera) colonies onPrunus aviumL.During the sampling period, 243 syrphid larvae belonging to seven species were collected fromM. cerasicolonies onP. avium. Episyrphus balteatusDeg. andEpistrophe eligans(Harr.) were the most numerous species amongst the materials gathered, followed bySyrphus ribesii(L.) andS. vitripennisMeig. All of these species play an essential role in reducingM. cerasipopulations. Amongst theCoccinellidaeoccurring in black cherry aphid colonies,Adalia bipunctataL. was the dominant species, while the subdominant wasCoccinella septempunctataL. andPropylaea quatuordecimpunctata(L.).

Aphid (Hemiptera: Aphididae) populations and the incidence of virus yellows on insecticide-free sugarbeet in south-eastern England in 1978-81

The populations of the most common aphid species on sugarbeet, and their principal predators, were monitored on insecticide-free study areas of the crop in south-eastern England in 1978–81. The peak populations of Myzus persicae (Sulzer) varied considerably in size from year to year and were related to the severity of the previous winter. Those of Aphis fabae fabae Scopoli, which occurred slightly later in the season, also varied greatly in size but were not strongly linked to winter temperatures. The sizes of the peak populations of Macrosiphum euphorbiae (Thomas) were similar each year. The annual variation in the level of infection by virus yellows reflected the peak populations of Myzus persicae and not those of the other aphid species. Coccinellids first appeared in the sugarbeet each year in mid-late June, as the aphid populations were developing, and their peak populations did not vary greatly from year to year. Syrphid larvae appeared later in the season than coccinellids, and their numbers seemed closely linked to those of A. f. fabae. Anystid mites were observed on most count dates in all years. The implications of the findings of the study for control of aphids and virus yellows are discussed.

COCCINELLIDS (COLEOPTERA: COCCINELLIDAE) AND SYRPHIDS (DIPTERA: SYRPHIDAE) AS PREDATORS OF APHIDS IN CEREAL CROPS: A COMPARISON OF SAMPLING METHODS

The reliability of three methods for sampling aphidophagous coccinellids and syrphids in a winter wheat field was compared.In the first method, an observer recorded predators seen during 2 min per 25-m2 sub-plot. In the second, two observers worked successively through each plot, scanning the full height of wheat plants and collecting predators. This method enables calculation of predator density using De Lury’s technique. The third method consisted of collecting wheat plants from each sub-plot for examination in the laboratory.The first method may be used for appraising populations of adult coccinellids on a large scale. The detailed searching method is appropriate for studies of the population dynamics of adult and fourth-instar coccinellids. The plant sampling method is the most accurate for assesssing densities of syrphid larvae and pupae.