Whitefly control
Eretline m
Eretmocerus mundus
Eretmocerus mundus
Eretline m is a proprietary product containing pupae of the whitefly parasitoid Eretmocerus mundus Mercet, Aphelinidae, Hymenoptera.
The initial commercial development of this beneficial was in response to the increasing problems caused by the Tobacco Whitefly, (Bemisia tabaci or(also known as Bemisia argentifolia) in various countries. Extensive testing by USDA showed that Eretmocerus mundus was a successful parasitoid of Bemisia tabaci. Eretmocerus mundus will parasitise Bemisia tabaci, but not the Glasshouse Whitefly Trialeurodes vaporariorum.
Unlike Encarsia formosa, Eretmocerus spp. are unable to turn within the host integument, so do not emerge well when attached to cards. Syngenta Bioline have developed a Blister Pack as an alternative method of distribution. This can be suspended in the crop in the same way as an Encarsia card. It makes the product clearly visible, and allows the grower to easily judge quality and emergence .
Eretmocerus mundus is native to southern Europe, North Africa and the Middle East.
Eretmocerus mundus is a parasite of Bemisia tabaci. It is in the same family as Encarsia formosa, and is similar in size and shape, but does not have the familiar black and yellow coloration. Instead it is a pale yellow or orange, and can be quite difficult to see amongst whitefly larvae. Unlike Encarsia, in which almost all the individuals are female, Eretmocerus mundus populations consist of males and females in almost equal numbers.
Eretmocerus mundus females search leaves for the young larvae of Bemisia tabaci. On finding a suitable host, they palpate it with their antennae and then turn to insert an egg between the host and the leaf surface. The larva that hatches from this egg burrows into the host larva, and a capsule forms around it. The larva initially lives within this capsule, but is not apparently damaged by it. Thus the capsule is different from those formed as part of the hosts’ normal immune response to parasitism. The host continues to feed and grow, and is only killed once it has fully grown and ceased to feed.
Females mainly select mainly second instar host larvae for parasitism, but will lay eggs under other instars. Egg laying is influenced by the leaf structure of the whitefly host plant: hairy leaves lift the margins of the whitefly larvae and make it easier for Eretmocerus spp. females to insert eggs beneath them. The host plant also influences the success of parasite development.
Whitefly parasitised by Eretmocerus mundus do not develop the black colour so characteristic of parasitism by Encarsia formosa parasitism. They are harder to detect within the crop, and so more careful examination of the host is necessary. Using a microscope, it is possible to see one or both of the yellow ‘mycetomes’, which are normally symmetrically placed either side of the midline, displaced to the side. As the pupa reaches maturity the darker yellow or orange of the adult can be seen with the naked eye.
Although Eretmocerus spp. females cannot penetrate the host cuticle with their ovipositors, they nevertheless kill large numbers of host larvae that do not develop into parasites. Females have been observed probing around the vasiform orifice of whitefly larvae, and it is believed that this is host feeding behaviour is . Up to 40% of the mortality which occurs has been attributed to this host feeding.
Eretmocerus mundus
Eretline m is supplied as pupae within ‘Blister Packs’.
Separate the blisters from each other by gently folding and tearing along the perforations.
Bend the card forward slightly at the top of the blister, and pull the tab outwards.
Hang the opened blister onto leaf petioles within the crop, so that it is in a shaded position.
STORAGE:
Use within 18 hours of receipt.
Keep at 5°- 10(C until use.)
Eretline m should be used wherever Bemisia tabaci is the dominant whitefly species present.
Eretmocerus mundus is better adapted to high temperatures, and those that fluctuate strongly from day to night, than is Encarsia formosa. It is behaviourally and physiologically adapted to deal with wide fluctuations in temperature, and exploit those times when temperatures are suitable for activity.
Eretline m should always be used preventively, before whitefly populations become established. High release rates may be able to reduce existing populations, but the cost will be high, and it may be more appropriate to use a compatible insecticide to reduce initial numbers.
Eretline m is supplied in a blister pack containing designed to provide 5,000 adults in total, as 20 blisters each producing 250 adult Eretmocerus mundus.
The blisters should be opened by gently flexing the card until the tab on the back of the blister can be pulled open. This tab then needs to be bent so that it does not re-close the blister. Opened blisters are then hung amongst foliage in the crop.
Use of Eretmocerus mundus is not recommended as a first option where there is a substantial risk of virus transmission from invading adult Bemisia tabaci. Other available biological controls are also not recommended in this situation, and use of an appropriate chemical remains the solution of choice. Eretmocerus mundus may then be introduced when the risk of invasion is lower.
Do not use Eretmocerus mundus where Trialeurodes vaporariorum is the pest. Where T. vaporariorum and Bemisia tabaci are present together, consider using Eretmocerus eremicus, or a combination of Encarsia formosa and Eretmocerus mundus.. On tomato (not except Cherry tomatoes) and Aubergine crops in Northern Europe the Mirid Bug Macrolophus caliginosus provides excellent control of both whitefly species after an initial period of establishment. It should be used in conjunction with Encarsia and Eretmocerus.
The predatory Phytoseiid mite Amblyseius (Typhlodromips) swirskii has recently been shown to control whitefly in some crops and some situations, and may be a useful addition to Bemisia tabaci control programmes. It is not suitable for use in crops grown at low temperatures.
Used as recommended, Eretline m will provide season long control of Bemisia.
Eretline m will not control existing high populations of Bemisia tabaci when used alone. Neither will it control Trialeurodes vaporariorum at any population density. It will not directly reduce adult populations of whitefly, and cannot protect crops from virus infection carried by invading adult whitefly. It may reduce the subsequent spread of viral infection by reducing the numbers of larvae which reach maturity.
A range of chemical insecticides may be successfully integrated with the use of Eretmocerus spp. Where the insecticide used affects the development of whitefly larvae, there will inevitably be an indirect effect on Eretmocerus populations due to the death of hosts. Thus young parasite larvae may die because of the death of the host, but in most cases mature larvae and pupae will survive, and the population will recover rapidly.
Some insecticides such as thiamethoxam, which have long persistence and produce high mortality when applied as a foliar spray, may be successfully integrated with the use of Eretmocerus spp. when applied as a root drench. Trials show that adult Eretmocerus spp. are not killed or repelled by drench applications, and are able to successfully parasitise whitefly larvae which survive treatment, or which establish after treatment. Percentage parasitism was higher on treated plots, and the whitefly population was lower.