Hydroponics BC

Pesticides, the natural way.

This is a great program of using natures own eco balance for your own needs. It reduces your pesticide use while increasing the overall health of the plant by not adding poisons. Anywhere that you can utilize biologicals I would encourage you because we all have to eat and sleep in this world and integrated pest management makes it that much easier.

The Problem


Red spider mite feeds on leaf cells causing yellowish, speckled marks. Depending on the degree of infestation, damage can range from small chlorotic patches, to dying leaves. Webbing can be found in extreme cases which leads to rapid spread of the spider mites to surrounding plants. The resulting damage can seriously reduce crop yields.

The Solution

Phytoselulus persimilis is a very efficient and cost effective way of controlling red spider mite levels in outdoor crops. Phytosefulus mites can be targeted where spider mite hot spots exist, and they will also travel considerable distances to actively seek out their prey. Whilst sprays can offer limited control, they often miss spider mites on the underside of leaves. Furthermore, harvest intervals should be carefully observed when spraying prior to fruiting. Phytoselulus can be introduced at any time after the risk of frost has passed.


Problem


Western flower thrips (WFT) and now to a lesser extent Onion thrips are serious pests on very many plants causing bleached patches on the undersides of leaves, and in severe attacks whole plants will be defoliated. WFT has become resistant to most pesticides since it was found attacking crops in Europe in the early 1980's.

Solution

Amblyseius available in a vermiculite formulation with 10,000 or 50,000/litre may be sprinkled onto low growing bedding or pot crops. Specially formulated breeding colonies of the predator are available in sachets for larger pot crops or salad crops. Orius spp is available in units of 250.

Benefits

CRS sachets provide predators before thrips invasions. Amblyselus can penetrate buds where thrips can avoid sprays. Orius supplement control in heavy infestations.

WFT - Biology of the pest

The life cycle takes between 2-7 weeks and the eggs are laid at a rate of 2-5/day. Adults live for about 6 weeks. Pupation usually occurs in the soil but it can occur on any horizontal surface. The pest over winters in the soil as a pupa and mobile stages can feed on any greenery left in the glasshouse.


Amblyseius cacumeris

This predator has been developed for use in a wide range of situations, with the unique controlled release sachets being ideally suited for use on long season crops (eg cucumbers, peppers). The colourless mite looks like a very small Phytoselulus and can be seen moving very rapidly over leaves. It eats 1 + young thrips larvae/day.

Orius spp.

There ore two species of Orius available in U.K. for WFT control. These are produced in bottles containing 250 predators in a buckwheat/vermiculite mixture. Orius laevigatus is preferable in shorter day lengths, whilst Orius majuscules being larger is also used in the summer months. Adults have been known to lay as many as 150 eggs at rates up to 3/day. The build up of population is dependent on temperature and prey levels, the life cycle taking 25 weeks. Being day length sensitive Orius laevigatus are normally introduced from mid-March and Orius majuscules from mid-late April.

Control

Thrips are difficult to control with chemicals and because of their very rapid multiplication rates Amblysefus should be introduced as soon as the first thrips are seen.

Control relies on complete cover of the crops with predatory mites, to catch young thrips larvae as they hatch. Orius on longer term crops would be applied at 1-5/ m2 but should not be used until the pest is seen attacking the crop.


Glasshouse Whitefly and its control

Problem


The glasshouse Whitefly (Trialeurodes vaporariorum) has been a serious pest of plants in glasshouses during the whole of this century. Both adults and larvae excrete copious amounts of sticky honeydew; black moulds grow on this, smothering plants and making them unsightly. Massive populations develop in plant heads, which together with the black mould kills the plants.

Solution

Encarsia is available on hooked cards (60/card) for hanging in the crop. They are provided in units of 25 cards. designed for easy application to plants. Use as an insurance to control Whiteflies as soon as they infect a crop.

Benefits

Quick and easy to use
Controls resistant strains of Whiteflies
Low cost treatment

Whitefly - Biology of the pest

Whiteflies can survive outdoors on plants even at temperatures below 0C where infestation can occur from weeds round the greenhouses. Once in the greenhouse adult flies lay eggs on young leaves After hatching ( 1-2 weeks) the young disc like larvae crawl over the leaf and settle. getting bigger with each moulting until pupation (1-2 weeks). The whole life cycle takes 3-7 weeks.


Encarsia formosa

These minute wasps (1.5mm long) attack young whitefly larvae (scales) by stinging and laying eggs within them. On pupation the Whitefly pupae turn black. Each wasp lays 60-100 eggs. and the life cycle takes 2-4 weeks to complete. The parasite will not fly below 20C. Introduction rates vary from 0.5-4 parasites/m2/week.

Control

Successful control depends on two important factors:
1. 'Insurance" introductions are made weekly
2. A temperature of 20C+ is required for a short while each day to allow the wasp to fly.

Some pesticides are lethal to Encarsia formosa. Contact your technical manager for guidance.

Practical use of Encarsia on crops

Cucumbers

Whiteflies overwinter on the smaller weeds so good clean up in the autumn is essential. Introduce Encarsia throughout the crop from 2 weeks after planting at 1-4/ m2/week.

Tomatoes

Parasites must be introduced throughout the season from ane week after receiving plants on the nursery until the heads are stopped. Care must be taken not to remove leaves with unemerged black scales. Use at rate of 0.5 - 1 parasite/ m2/week.

Ornamentals

It is especially important to clean up glasshouses before introducing new crops. This is sometimes difficult where stock plants are overwintered. In all situations introduce Encarsia at 1-3/ m2/week.

Poinsettias must have Encarsia introduced onto the crop from receiving the plants until 2 weeks before marketing. Use 1 parasite/3 plants.

Sticky yellow traps are valuable in monitoring for adult whiteflies.

Note:
Another species of Whitefly, Bemisia tabaci (the cotton whitefly) is potentially a very serious pest of many glasshouse crops. At present it is controlled under plant quarantine regulations.


Aphis gossypii and its control

Problem


Aphis gossypiis a pest of many crops covering leaves with honeydew which encourages the growth of sooty moulds and virus transmission. The pest has become resistant to many pesticides except those which disrupt other systems of biological control used in the glasshouse. Therefore control using Aphidius colemanior Aphidoletes aphidimyza is highly preferable.

Aphis gossypii - Biology of the pest

Aphis gossypii can appear in the glasshouse at any time from April to September. They appear as winged adults which then reproduce asexually very rapidly to form large colonies of phloem feeding aphids.

Aphidius colemani

The parasitic wasp will lay a single egg in the aphid host by inserting its ovipositor. The Aphidius larva develops within the aphid and consumes the entire body contents. The mature larva cuts a slit in the underside of its host and attaches it to the leaf after which it spins a cocoon and pupates. At this stage the aphid resembles a swollen. papery 'mummy'. The adult Aphidius cuts a round hole in the aphid cuticle and emerges. The life cycle takes approximately 3 weeks and a single female will attack up to 300 Aphis gossypii.

Benefits

Easy and covenient to use.
The natural enemies are winged and therefore extremely mobile.
Overcomes the problem of resistance to chemicals.
Completely safe to use.

Control

Ongoing trials suggest the following introduction rates.

Preventative - when the risk of invasion by Aphis gossypii is high, introduce 0.5 per m2 weekly.

Curative - Once Aphis gossypii has been seen increase rate to 2 per m2 for 3 weeks, concentrating Aphidius in the worst affected areas.

Warning
Failure to detect early infestation may result in the removal of badly infested leaves becoming necessary.

Aphidius and Aphidoletes should be applied on the day of receipt. Bottles should be opened near infected areas. Aphidoletes can be split into smaller receptacles containing moist peat and spread around. In badly affected areas bottles of Aphidius can be hung within the crop.

Some pesticides are harmful to Aphidius and Aphidoletes. Consult your Technical Services Managers for guidance.

Always read the instructions on the product label.


Aphidoletes aphidimyza

The small, nocturnal midge lays eggs beside aphid colonies and the orange coloured larva hatches to feed on the aphids. The larva bites aphid knee joints and injects a paralyzing toxin after which it sucks out the aphid's body fluids. A larva will kill up to 50 aphids during its lifetime. The larval stage lasts about 5 days and the life cycle is complete in 3 weeks. A female will lay between 100 and 200 eggs.

Warning

Aphidoletes will hibernate when day length falls to less than 15.5 hours. This can be avoided by the use of low intensity lights.

Control

At the first sign of Aphis gossypii or other aphids 2 to 5 Aphidoletes should be introduced per m2 for at least 3 weeks.

NB. Aphidoletes alone will not be suitable for the control of Aphis gossypii in cucumber crops. Practical use of Aphidius & Aphidoletes on crops.

Cucumbers

Introduce Aphidius colemani as a preventative measure when Aphis gossypii is known to be appearing in the area or as a curative measure when first seen in the crop. Effective monitoring is vital so that outbreaks can be dealt with immediately. It may be necessary to remove badly affected leaves or to spray them with soft soap to disperse the aphid colony. Preventative introductions should be at the rates of 0.25 - 0.50 Aphidius per m2 per week.

At first sighting of Aphis gossypii introduce 0.50 Aphidius per m2 per week, and in hot weather or in high levels of infestation 1.00 per m2 per week will be needed.

Ornamentals

Introduce Aphidius colemani as a preventative measure from the beginning of the season at 0.5/m2 every two weeks. Monitor carefully so that invasions from outside the glasshouse late in the season may be dealt with quickly.

Aphidoletes may be introduced preventatively but will be more effective after aphid colonies are established.

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