Whitefly control

Macro-line c

Macrolophus caliginosus

 

 

How does it work?

All mobile stages of Macrolophus caliginosus, from the first instar to the adult, are voracious predators. They prey on many small invertebrates, but field experience and laboratory studies have shown that whitefly are one of the best foods, giving high fecundity and attracting Macrolophus into crops in regions where it is native. Macrolophus also thrives on eggs of Lepidoptera, and will take some nutrients from plants.

Macrolophus females insert eggs singly into the stems and thicker leaf- veins of plants. These eggs are extremely difficult to see, even with a microscope. At average temperatures of 23°C, the eggs hatch about two weeks after laying, and the larvae become adult about three weeks later.

There is then a further week during which time females mate and develop before they become capable of laying eggs. The generation time at 23°C is therefore six weeks, and at lower temperatures will be substantially longer.

This long generation time makes initial control by Macrolophus slow, and it may be one or more generations before they become easily visible on the crop. Because of this slow build up, it is usual to use Encarsia formosa as an additional control until Macrolophus is well established.

When established on the crop Macrolophus makes a significant contribution to the control of other pests such as spider mite, caterpillar and leaf-miner, but is not recommended specifically for control of these pests. Spider mite in particular is a poor quality diet, and results in slow growth and low fecundity. It is important to note that Macrolophus caliginosus and other generalist predators may have prey preferences, and ignore one potential pest in favour of another thatwhich they prefer. Control of these less favoured dietary items will always be unpredictable.

In the wild, Macrolophus caliginosus is associated with sticky, aromatic plants such as Inula viscosa. It naturally invaded whitefly infested tomato crops in Southern France and controlled whitefly populations when present in sufficient numbers. While it is known to invade cucumber crops in the Barcelona region of Spain, augmentative releases further south have generally failed. The population in those regions reaches sufficient numbers only at the end of the crop, and does not significantly contribute to whitefly control.

When and where should you use it?

Macro-line c was developed specifically for control of whitefly on tomatoes.

It is recommended for use on tomatoes and aubergines only. Cherry tomato varieties can suffer damage from Macrolophus caliginosus if high populations build up.: Aas pest populations decline, the Macrolophus become more phytophagous, and this behaviour can result in fruit drop. This problem is not encountered by all growers, so some other, as yet unidentified, factors may be involved. Establishment on peppers is very variable, and the product is not recommended on this crop or cucumbers.

On tomatoes and aubergines, early release gives the best result. Release rates of 0.25-1/m² are recommended, depending on previous seasons experience of whitefly problems. Initial releases should always be accompanied by use of Encarsia formosa for control of Trialeurodes. Once Macrolophus is established, releases of Encarsia can cease. Where other pests are present appropriate chemical or beneficial treatments should be made, and Macrolophus should not be relied upon to give control.

How should you use it?

Release Macrolophus as uniformly as possible throughout the crop, preferably in subdued light early or late in the day to avoid adults flying directly to the vents.

Open the pack where it is needed, and walk along the plant rows, lifting and gently shaking the wood wool to distribute the adults. Leave the packaging at the base of a plant to allow any remaining adults to leave.

When should you not use it, and what are the alternatives?

Macro-line c has been reported to cause some leaf damage and fruit loss in some tomato crops in Britain, and a few in Holland. No similar damage has been reported from France or other countries.

Cherry and vine ripened tomatoes are most at risk, and to avoid the possibility of damage, Macrolophus should never be used on these crops.

On these crops, a traditional preventive programme of Encarsia releases will provide good protection. Corrective treatments with buprofezin, pymetrozine, insecticidal soap or other compatible chemicals can be used to reduce locally high populations of whitefly. If Bemisia is present, or summer temperatures will be higher than 30°C for extended periods, use Eretmocerus eremicus in addition.

It should not be used on ornamental crops without a trial treatment of a small number of isolated plants.

What will it do?

Macro-line c will help prevent the build-up of high whitefly populations in round tomato and aubergine crops when used as recommended. It will also contribute to control of other pests once it has established.

What will it not do?

Macro-line c will not quickly reduce high existing whitefly populations unless used at very high rates.

It is not recommended for use to control other pests such as spider mite, although once established in the crop it will contribute to their control.

It is not recommended for use on cucumber or pepper crops because of poor establishment, and the availability of effective alternatives.

Chemical compatibility

A number of chemical insecticides can be integrated with the use of Macrolophus caliginosus. Some will result in a reduction of the population as a result of direct toxicity to certain stages, or as an indirect result of prey removal.