on leafminer Liriomyza spp

Transcription

1 real insights on leafminer Liriomyza spp real insights is published by Real IPM (Kenya) Ltd Follow for more real insights Real Solutions: Real Farming

2 Plants need healthy leaves to capture the energy of the sun and turn it into food to fuel plant growth. the yield of the crop, or reduce the sugar content of fruits. Cosmetic damage to the leaves of ornamental plants, due to the presence of mines, may reduce quality and value. Melon fruits need large leaves to produce the sugar needed for top quality fruits. See leaves damaged by leafminers. TRADE BARRIER exported produce could lead to rejections in the country to where the produce is exported. If the problem is persistent the importing country has the right to suspend imports until the plant health authorities can guarantee the in-country problem is under control again. Vegetable leafminer Liriomyza. sativae South American Leafminer Serpentine Leafminer, Pea Leafminer, Liriomyza. huidobriensis American serpentine leafminer Liriomyza trifolii 1 Real IPM (Kenya) Ltd

3 RISK ASSESMENT with chemicals alone and an IPM programme is essential: Leafminer is already resistant to a number of chemical pesticides. Many contact and systemic action chemical pesticides can kill from 25% to harmful effect can last from 1 to 12 weeks, depending on the active ingredient. The leafminer larvae are inside the leaf, so are only susceptible to systemic pesticides, which usually have a longer Pre Harvest Interval, making them impossible to use throughout the cropping period. Some of these organophosphate chemicals are now banned by retailers or governments. But leafminer larvae inside the leaf ARE attacked by leafminer parasitoids (if harmful chemicals have not been used). The leafminer pupae in the soil are not targeted by chemical pesticides. This leaves a reservoir of leafminer that can emerge from the soil as adults and continue attacking the crop. But commercial bio-pesticides such as Real Metarhizium 69 could infect and kill the pupae in the soil, if it is applied to the top surface of the soil where the leafminer pupates. 2 Real IPM (Kenya) Ltd

4 Designing an Integrated Pest Management (IPM) programme begins with understanding the life cycle and behaviour of the pest, so that appropriate interventions can be implemented. A female on average will live for about a week, whereas male leafminers die within a couple of days because they cannot puncture and feed on leaves. Feeding marks in leaves are small, circular, white dots, whereas egg-laying punctures are more oval in shape. LIFE CYCLE AND BEHAVIOUR Female leafminers lay eggs in the leaves, which hatch into larvae within 4 7 days. The larvae feed on the fleshy part of the leaf. This creates a characteristic tunnel or mine in the leaf blade. The larva can be seen at the far end of the tunnel. (below) When the larva is fully fed, it will pupate, either on the leaf surface or drop to the soil, near the plant. in 1-2 weeks, and the cycle begins again. Several generations per year are possible, if the conditions are right. The life span of these pests is days. Female leafminers can lay more than thirty eggs per day and from 200 to 400 eggs in a very short lifespan. Typically they feed and oviposit during much of the daylight hours, but especially near mid-day. When temperatures exceed 40 C leafminer lay fewer eggs. 3 Real IPM (Kenya) Ltd

5 Knowing where and when leafminer adults are likely to be in a crop, will allow growers to target their interventions more effectively. BEHAVIOUR OF LEAFMINER ADULTS are often found taking refuge in the shade during the heat of the day. French scientists in Reunion Islands discovered that planting a barrier of maize plants around low growing crops, manner at certain times of day. where they went for shade. crop in the middle of the day. They are more likely to be found in the windbreaks This made them an easier target for spraying a control agent. It is likely that this tactic may also have a part to play in the control of leafminer Melon growers in Brazil, working with spent most of the middle of the day in the neem tree windbreaks around the edge of 4 Real IPM (Kenya) Ltd

6 LEAFMINER TRAP PLANTS Adult leafminers are also very attracted to the colour yellow and can be trapped on yellow sticky plastic. However, the parasitic wasp for leafminers can also be trapped and killed on the same sticky trap. A yellow plastic sheet without the glue can pull leafminer to a certain place, where a different intervention can be planned, that will not kill Diglyphus. HARVESTING DIGLYPHUS FROM CROP WASTE The attractiveness of the broad bean plants can be enhanced if a yellow plastic strip is also positioned near the trap plants. The yellow strip should not have glue on it so that the parasitic wasp, Diglyphus can also live in the trap crop. - tive to leafminers than others. Such plants include broad beans and spinach. These If the broad beans, are not sprayed with chemical pesticides, they will attract leafminer; the leafminer larvae in the leaf will attract indigenous Diglyphus or other parasitic wasps, that lay eggs in the leafminer larvae. (below) allowing the leafminer to lay more eggs in the trap plants (instead of the crop). Eventually the majority of the mines that can be seen in the leaves will be parasitized and contain Diglyphus. 5 Real IPM (Kenya) Ltd

7 The old, badly damaged, broad bean trap plant or old crop waste (post harvest) could be placed into large cardboard boxes with plastic jars inserted in the outside (below left). As the Diglyphus hatch form the parasitized leafminer mines, they will fly to the light and can be harvested from these jars. The harvesting takes place twice per day and each time new empty jars replace the ones that have been removed, containing newly hatched Diglyphus (below right). Harvesting of Diglyphus and other leafminer parasitoids can be a very cost leafminer parasitoids. The harvested leafminer parasitoids must be kept cool and used as quickly as possible after harvest. Polystyrene boxes with ice packs are a simple way of creating a cool chain system. 6 6 Real Real IPM IPM (Kenya) Ltd Ltd

8 USING CROP WASTE IN THE FIELD The farmer needs to calculate the risk of leafminer-infested crop debris causing a problem due to emergence of too many leafminer compared to more Diglyphus than leafminer, emerging from the leaf. If the ratio of Diglyphus to leafminer is smaller than 1: 6 then the crop debris into loving crops nearby. There will be more Diglyphus than leafminer hatching form this crop waste and enough Diglyphus to help protect the new crop. A ratio of 1: 6 means that for every one Diglyphus adult there is only 6 leafminer adults in the crop. There is no need to dissect leaves to calculate this ratio. Simply scout the crop and count the number of Diglyphus adults or leafminer adults sitting on leaves in the sample area. The larger the area sampled, the more reliable the data. Parasitized crop waste is placed along the border of a commercial crop, so that the Diglyphus can migrate into the crop to attack the leafminer pest. 7 Real IPM (Kenya) Ltd 7 Real IPM (Kenya) Ltd

9 TIMING THE INTRODUCTION OF DIGLYPHUS It is possible to purchase a range of leafminer parasitoids from biological control companies but they tend to be very expensive. A minimum of 12,000 Diglyphus might be required per hectare to make any impact on leafminer. Of course the Diglyphus should not be applied to the crop, until there are at least a small number of leafminer mines in the leaf, because they need a leafminer larvae to reproduce. Timing is critical. COMPATIBLE BIO-PESTICIDES Real IPM bio-pesticides are compatible with predatory mites and parasitoids for leafminer and other pests. If a prophylactic preventative programme of bio-pesticides is used correctly there COMPATIBLE PESTICIDES from Diglyphus as a parasitic wasp against leafminer unless compatible fungicides and insecticides are used for all other pests and diseases in the crop. For example, many of the pyrethroid insecticides will kill up to 75% of the Diglyphus, which either migrate naturally into the crop, or applied to the crop. This harmful effect can last for up to 12 weeks. This means that within 10 to 12 weeks of applying one application of a pyrethroids insecticide up to 75% of all Diglyphus that enter the crop, could die. Fewer pests in the crop More parasitoids and predatory mites in the crop Less chemical pesticide residues Resistance Management for important chemical insecticide active ingredients. The Real IPM Pesticide Compatibility Charts are soon to be uploaded onto our website We also run training courses on how to design a Compatible Spray Programme. 8 Real Real IPM IPM (Kenya) (Kenya) Ltd Ltd

10 HOLISTIC REAL IPM PROGRAMMES The Real IPM product range includes bio-fungicides and bio-insecticides for a wide range of pests and diseases. Real Bacillus subtilis (rust, powdery mildew, leaf spots, botrytis) Real Trichoderma asperellum (soil diseases, botrytis, downy mildew) Real Metarhizium 69 (leafminer, Real Metarhizium 78 (spider mite) (Trade name Achieve) Real Metarhizium 62 (aphids) Check for your in-country Registrations for these bio-pesticides. In South Africa, Real Bacillus subtilis and Real Trichoderma asperellum are also Registered as bio-fertilisers, so they can be used on any crop. REAL IPM TRAINING Real IPM also produces a wide range of predatory mites, which have a useful target range and are compatible with the above bio-pesticides. Phytoseiulus persimilis (for spider mite curative programme and hotspot control) Amblyseius montdorensis (for - der mite when present as a single pest or together). Amblyseius cucumeris (for thrips 1st instar) Amblyseius swirski (for thrips 1st are also present at the same time). Amblyseius californicus (for spider mite prevention not curative works best in hot temperatures) Amblyseius andersoni (for spider mite prevention not curative works best in cool temperatures). Real IPM produces all its predatory mites under license from Syngenta Bioline in UK. Real IPM can provide on-farm training on Holistic programmes, compatible spray programmes and resistance management. See our website for more information. 9 Real IPM (Kenya) Ltd

11 REAL METARHIZIUM REAL METARHIZIUM Real IPM (Kenya) Ltd has commercialised a number of entomopathogenic fungi (Metarhizium anisopliae) from icipe an international research institute based in Nairobi, Kenya. Metarhizium anisopliae is a ubiquitous, naturally in the soil and when taken out of the soil and mass- produced as a bio-insecticide, it will not persist for more than about 12 hours in the canopy because UV light kills it. Metarhizium 69 has been tested Metarhizium 62 has proved effective against aphids and leafminer Metarhizium 78 infects spider mite, tarsonemid mites, varroa mites and leafminer. PEST-SPECIFIC METARHIZIUM ISOLATES If the Metarhizium spore lands on an insect pest s body and the spore can recognise the pest, only then will it germinate. The process of recognition makes the many different isolates of Metarhizium Scientists at icipe have screened the above isolates against leafminer and found that all three isolates are able to kill adult Liriomyza huidobrensis, using an auto-dissemination device. This means that if a prophylactic preventative spray programme is used for any of the other pests listed above there will be a are not broad spectrum in the same way as some chemical insecticides. This is why each different Metarhizium isolated from the soil is named with a different number. 10 Real IPM (Kenya) Ltd

12 COMPATIBILITY OF METARHIZIUM It will only succeed in the infection process if it can overcome the insects on immune system, during its growth through the cuticle and epidermis of the insect s body. Once inside the haemocycl of the insect, it will produce a different type of spore that will reproduce by using the nutrients in the haemolymph. Eventually the insect dies. This may take 3 to 5 days. The cadaver may disintegrate with conidia of Metarhizium on the surface. Metarhizium, as a backbone to an IPM programme, in a prophylactic preventative programme, is that it does not appear to kill the predatory mites or parasitic wasps that also attack these pests. This makes Metarhizium a very useful tool, when needing to change the balance between the pest and the predatory mite or parasitic wasps. The Metarhizium will kill more of the target pest, allowing the smaller number of predatory mites or parasitic wasps, to make a bigger impact on overall pest levels. Metarhizium has no mammalian toxicity because it cannot grow at human body temperatures. insect cuticle epidermis appressorium conidia INFECTION PROCESS If the Metarhizium spores land on a pest that it can recognise; it will germinate and begin searching the insect s cuticle for a thin place (integument or opening) where it will form a special pad (appressorium) and then begin excreting enzymes that will help it to penetrate the cuticle. If it does not recognize the host the spore dehydrates and dies within about 12 hours. haemolymph blastospore 11 Real IPM (Kenya) Ltd

13 FORMULATIONS AND APPLICATION RATES Real IPM Kenya produces two formulations of Metarhizium 69. One formulation consists of pure spores which is applied at 200 to 400 ml per hectare. The other is a Total Fermented Product (Met 69 TFP), which is a liquid formulation containing mycelium and two types of spores. It is applied at 1 to 2 liters per hectare. IDENTIFICATION AND LIFECYCLE OF DIGLYPHUS Diglyphus is a very tiny ecto- parasitic wasp, which means that it lays eggs near the larvae (not inside it). The adult will antennae onto the leaf surface to feel the vibrations of the feeding larvae as it tunneling process. A third formulation is pure spores in an inert powder, which is used in control. Seek advice from Real IPM. Check Real IPM s website for Diglyphus egg (yellow) laid on outside of leafminer larvae (white) The Diglyphus egg will hatch and then begin feeding on the leafminer larva killing it. A good sign of a high rate of parasitism is a lot of short mines in the leaves as a result of the death of larvae due to parasitisation. If the leafminer larvae are big, there may sometimes be more than one Diglyphus egg laid on the larvae and more than one Diglyphus wasp will later hatch from this mine. Mines in a leaf therefore do not mean that there is a serious problem with leafminer if the: ratio of adult Diglyphus to leafminer is less than 1: 6 (Diglyphus to leafminer) mines are all shorter than usual due to parasitism. 12 Real IPM (Kenya) Ltd

14 LEAFMINER PARASITOIDS The two main genus of leafminer parasitoids are Diglyphus and Opius. Both of which can be very common in the wild and are also mass-produced by some bio-control companies. These bio-control agents can be quite expensive and their use is largely outdoor crops of lower value, it is probably more cost effective to try to manage bio-diversity in the way described in this treatise. Diglyphus has short antennae, (below left) whereas Opius has longer antennae (below right). Both parasitic wasps will be found in association with leafminer mines, making them easy to identify. Real IPM (Kenya) does not currently mass-produce leafminer parasitoids because prophylactic programmes of Metarhizium 69 in biological control to form an effective IPM programme. A bio-intensive programme with Metarhizium as a backbone, will allow indigenous leafminer parasitoids to contribute more effectively to the control of this pest. If necessary, Met 69 can be tank-mixed with insecticides for leafminer as a resistance management programme for the chemical active ingredient. By tank mixing the Met 69 with a chemical insecticide there is likely to be a measureable synergistic effect. This could be due to the chemical compromising the pest s immune system and allowing the Metarhizium to work faster. As the Diglyphus larvae feeds on the leafminer body, it creates pillars of its faeces to hold up the empty tunnel in the leaf and provide space for it s own pupation inside the leaf. The black dots surrounding the green Diglyphus pupae (bottom left) are these columns of faeces. The Diglyphus pupae (bottom right), has been dissected from the leaf to show the green pupae with red eyes. MONITORING METHODS The use of yellow sticky traps is a very method. Contact Real IPM for Entrap and Monitrap stick traps However, it is not advisable to use these routinely or for mass trapping except in severe infestations, since the yellow sticky traps also catch Diglyphus, which is a very controls this pest without the need for any pesticides. Leafminer prefer to sit on horizontal surfaces rather than vertical surfaces and will therefore be more effective if placed horizontally in the crop. 13 Real IPM (Kenya) Ltd

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