Friday, May 7, 2021

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Home Issue 4 Grasshoppers declare war

Grasshoppers declare war

By GEOFF MIERS

Grasshoppers are emerging in large numbers, starting to invade home gardens, attacking a wide range of plants causing considerable damage to the foliage.

Remember also while the grasshoppers are doing some damage the birds, lizards and even spiders are having a lovely time and feasting to their hearts’ content.

However, these creatures, while reducing the numbers, are only doing so marginally and the home gardener maybe required to follow the call to arms.

Grasshoppers can be managed by adopting a varied battle plan.

While there can be a role for many of the alternative methods using barriers, traps and deterrents, largely a successful grasshopper elimination program relies on chemical and technical warfare.

For example, a kid’s swimming shell if lined with yellow plastic and then filled with water will attract grasshoppers and they simply land and then drown.

I manage to incorporate a range of activities in my garden and my two nurseries to manage the thousands of grasshoppers that emerged over a two months period in 2016 when we really experienced a plague.

Walk around your garden in the early morning looking for baby grasshoppers emerging from the soil.

If they are present they will emerge in their hundreds and quick action will remove them while they are young. Once the grasshoppers mature they are not so easy to eliminate.

These baby grasshoppers, less than one centimetre in length, are easy to eliminate. A spray with pyrethrum or fly spray will quickly bring about their demise.

If using fly spray you must wash down the plants you have sprayed as the spray can result in leaf burn. Wait until the grasshoppers have hopped away and immediately wash down your plants.

If spraying with pyrethrum don’t forget to add a little white oil or dishwashing liquid to improve stickability.

Pyrethrum is an extract from a daisy plant and has a half live of 12 hours, it essentially is used as a contact spray.

It breaks down quickly in sunlight and 24 hours after spraying on vegetables for example you can harvest the vegetables and wash them and prepare them for consumption.

Remember also that pyrethrum is only effective on very young grasshoppers it will not work on adult grasshoppers.

As I walk around my nursery hand watering in the early morning or in the evening I always have a can of fly spray with me to particularly catch the odd large grasshoppers. One night in 2016 I sprayed 30 very large grasshoppers, knocked them off the plant and then washed the foliage to remove the fly spray.

Alternatively I attempt to physically catch them by hand. This method is largely adopted as I wander around my nurseries or garden during the day. Twice or three times a day I wonder around looking for these destructive hoppers. One large grasshopper can cause a lot of damage in one day on one plant.

Actually the best way to catch large grasshoppers is to wander around your garden after dark with a powerful torch. They will simply sit there and not move and you can walk right up and spray them or simply physically catch them and tear their heads off.

If you are not comfortable with catching them then approach them with a pair of secateurs and simply cut them in half. Not really a nice thing to do however its them or your garden.

Wandering around the bush yesterday there literally must have been thousands feasting on the new growth following the recent rains. 

For not food producing plants I use a chemical called Carbaryl, it is by far the most effective chemical management tool. It will see them die within an hour or two.

Carbaryl sprayed on foliage is also effective for several days. Any grasshopper that consumes any foliage that has been sprayed with Carbaryl will also die.

Until two years ago Carbaryl was recommended also for food plants with a withholding period of three to twenty days. It today is however not recommended in Australia.

America as an example still approves the use of Carbaryl on food plants with over 11 million tonnes of Carbaryl used annually on home garden food plants and in large scale agricultural farms.

In my production nursery I find I have to spray every two weeks with Carbaryl to manage large outbreaks when they are a problem, although I haven’t been confronted by a grasshopper problems for five years.

As an alternative to using Carbaryl on food plants Malathion can be used as its use is still approved for food plants.

Malathion is a contact spray and must be sprayed onto the grasshoppers to result in their demise. Malathion will result in their demise quickly.

Malathion has a withholding period of three days for vegetables. After spraying vegetables shouldn’t be harvested for at least three days and I recommend you wash the vegetables down prior to using in cooking.

Many people do not like to use Malathion as it has a strong odour, people generally associating the smell with it being a nasty chemical. This is not necessarily the case.

In the case of ornamental plants in pots I have had most encouraging reports of Confidor tablets being most effective on grasshoppers.

These tablets will slowly release a chemical that is absorbed into the sap stream of the plant for several months. The tablet approach is not recommended for food plants.

Confidor also comes in a granular form however it is marketed under the title “Bug Killer”.

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