Insects in peril

Sunday, 03 March 2019

Bumble bee in the Garden of Heligan, England

In my younger gardening years, I would probably have thought, 'Yay!' on hearing that numbers of all kinds of insects are in sharp decline, with recent estimates being a 45% drop worldwide over the past four decades, and predictions that 40% of the planet's insect species will be extinct in the next few decades. A little wiser nowadays, I realise what important roles insects play in our ecosystem: as vital pollinators of plants, including important crops; as food for birds, bats, amphibians, reptiles and other creatures; as predators for destructive insects; as helpers in breaking down decaying matter in the environment; and, in some cases, controllers of weeds.

Bogong moth

Just last week an alarming report illustrated this problem close to home, noting that Bogong moth numbers in alpine areas in Australia this year are catastrophically low, leading to a lack of a key food source for the endangered mountain pygmy possum population as they breed and raise their young. The cause of the drop in moth numbers has been attributed to ongoing drought and unusually high summer temperatures in this region.

Bug on Dahlia Moonfire

Along with changes in weather patterns (particularly an issue in tropical climates), other causes of insect decline include loss of their habitat caused by deforestation, conversion of land to intensive monocultural agriculture and increasing urbanisation; use of pesticides, especially neonicotinoid chemicals that are harmful to many insects; overuse of nitrogen fertilisers in farming, which pollute the wider landscape and reduce biodiversity amongst plants, enabling only a few dominant species to prosper; and the use of herbicides that have destroyed various wild food sources for insects.

Butterfly on lavender

Unlike other environmental issues, where we gardeners can do very little to make a difference, in this case there are small steps we can all take in our own gardens to help. Probably the most important one is to stop using harmful pesticides in our gardens, especially the neonicotinoid-based ones such as Confidor, which are absorbed through the whole plant and can poison any insect that visits its flowers. Many retailers are voluntarily withdrawing them from sale in Australia, which is very commendable. It's a big step to use no pesticides at all, not even the organic ones such as horticultural oils, and I don't know if I can give these up just yet, but I am working on myself with this! Another constructive step we can contemplate taking is to eat more of organically produced food, supporting farmers who are eschewing dangerous chemicals (or grow our own without the use of harmful pesticides).

Orlaya grandiflora with rose Betty Prior, in the garden of Sandra Wilson in Sydney

Another next step we can take is to include in our gardens a diversity of flowering plants to attract insects in their search for food. Plants with single flowers (as opposed to hybridised double flowers) are preferred, and many insects are particularly drawn to the tiny flowers of the Apiaceae and Asteraceae families of plants. Plants such as Queen Anne's lace and Orlaya, along with herbs such as parsley, coriander and chervil allowed to go to flower, are some of the Apiaceae plants, and the Asteraceae family includes all the many and varied daisy plants. Plants from the broad Lamiaceae family also seem to be particularly favoured. However, all flowering plants have their insect pollinators, especially our native flora, and it is also helpful to have a succession of flowering plants throughout the year, so that there is always something in bloom in the garden. Another good reason for us gardeners to acquire more plants!

Insect hotel

Providing a water source for insects is also vital, even if it is just a shallow dish somewhere in the garden. A more challenging step is to leave some of the garden a bit 'untidy', especially over winter, to provide shelter and habitat for insect species. There are some cute insect 'hotels' that can be bought these days, or you can make your own out of lengths of bamboo and other hollow material. Allowing a few weeds here and there is another idea, as these may be a source of food for certain insects. This can be my justification for weedy areas in my garden in future!

It's easy to love butterflies, dragonflies, ladybirds and bees in the garden, but developing an ability to embrace the presence of less lovely insects is something of a greater challenge! Bronze orange beetles, lily borers and mosquitoes are just a few of the horrors that come to mind. I am going to try to find physical methods of controlling them on my plants then leave them for the birds to eat. Tolerating a few holes in leaves gnawed by insects is not the end of the world, either, as I try to tell myself. Hopefully, other creatures will come along and eat many of the less desirable insects if we can re-establish a more natural balance in our gardens over time!

Another thing that gardeners can do is to take on the role of being a 'citizen scientist' and help document the numbers of insects in your vicinity, to help scientists get a more accurate picture of what is happening. One such program, called the Wild Pollinator Count, is currently being run in Australia, and you can find more about it here. Count dates for this year are 14-21 April and 10-17 November.


Plant of the week
Flowers in March, April, May, June, July, December.
See everything that's out this month »

My previous blogs at this time of year:
2009
02 Mar
2010
07 Mar
2012
04 Mar
2016
06 Mar

Reader Comments

  • By Margaret - 2122 (Zone:10 - Warm Temperate) Monday, 04 March 2019

    I heard, with horror, the decline in all kinds of insects, throughout the world. I don"t use anything toxic in my garden and try to encourage insect visitors by planting a wide variety of flowering plants. In the last couple of months, I have been delighted to find four kinds of bees, numerous types of wasps, and other unknown insects, and, best of all, three kinds of butterflies visiting. The latter have been scarce for some time, so I am pleased to see their return. Lovely that you have such a range of insects in your garden, Margaret! I am sure they enjoy all your flowers. Deirdre

  • By Kerrie - 2104 (Zone:10 - Warm Temperate) Monday, 04 March 2019

    Fabulous blog Dierdre!I"m going to follow that link. To me, the elephant in the room regarding all environmental issues nobody wants to talk about is overpopulation of the human kind. The earth even at it"s healthiest can only sustain so many people & I wish people would consider this before planning their families. Thanks, Kerrie. Deirdre

  • By Patricia - 2100 (Zone:10 - Warm Temperate) Monday, 04 March 2019

    Another richly researched blog...thanks once more for sharing valuable information and enthusiasm for keeping our gardens beautiful and environmentally sound. "...and I say to myself, it"s a wonderful world". Thanks, Patricia; I am glad so many people feel the same way. Deirdre

  • By Beth - 2257 (Zone:10 - Warm Temperate) Monday, 04 March 2019

    I do keep a slightly wild garden in spots. I find the swan plant is marvellous as a butterfly host. Once you have this in the garden it takes care of itself renewing after being ravaged by the butterfly caterpillars. It pops up but is very easy to remove if in the wrong place. The bog sage attracts blue banded bees, along with perennial basil. Planting natives also helps support the whole eco system. Midgin berry is a marvellous small (1 metre square) that feeds the local bower birds. Thanks for those suggestions, Beth. Deirdre

  • By Jennifer - 2193 (Zone:10 - Warm Temperate) Monday, 04 March 2019

    Have just resubscribed. Thankyou very much for this blog. Thoughtful and well written. Jennifer Hillier. Thanks for your feedback, Jennifer Deirdre

  • By Ken - 2203 (Zone:10 - Warm Temperate) Monday, 04 March 2019

    Dierdre, Thanks for this; as I think I said before, i always look forward to reading them. I agree wholeheartedly with what you say about insects. It put me in mind of my latest reading matter which is "The Informed Gardener" by Linda Chalker-Scott from Washington State U.. She debunks gardening myths based on scientific research. A lot of what she says just makes common sense, but she has some interesting ideas, too. She is opposes to digging and turning the soil, for example (continued)

  • By Ken - 2203 (Zone:10 - Warm Temperate) Monday, 04 March 2019

    (continued) because of burying the living top layer. This is a practice I have followed for years, based on laziness rather than scientific research. I have copied a section about "organic" gardening for you which I"ll send separately. I was sorry that our planned visit didn"t happen. Perhaps we can try another time later in the year. Regards, Ken Swinbourne Thanks very much, Ken. Hopefully we can catch up some day. Deirdre

  • By Sue - 2074 (Zone:10 - Warm Temperate) Monday, 04 March 2019

    Thanks for a great blog. Standing watering this morning and watching various insects in the garden I noted that there were some I did not recognise, so was glad to have the link to the Pollinator site you have mentioned - lots of pics for ids. I will be doing the count this April. I let parsley and celery flower & seed this summer and it was amazing to see the bugs that visited. A Blue banded bee has taken up residence in a small round hole near the front door. Tricky, but its ok if you know.Insects seem to really like veggies and herbs that have gone to flower! Deirdre

  • By Bren - 2540 (Zone:10 - Warm Temperate) Tuesday, 05 March 2019

    Thanks Ken for the reference to the "The Informed Gardener". It"s a very interesting bog/site: almost as good as this one!

  • By Pam - 2159 (Zone:10 - Warm Temperate) Tuesday, 05 March 2019

    Hi Deirdre,You don"t mention the trend for so many gardens to be just trimmed lawn, trimmed box hedges, and shrubs trimmed into topiary balls. Insect, especially bees, need FLOWERS. A visit to a native garden, such as Boongala Gardens at Kenthurst, is alive with insects amongst the grevilleas and bottle brushes. This is a great point, Pam; thanks for bringing it up. Deirdre

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