Caterpillars are still causing crop damage nearly two weeks into June

It is simply astounding (not in a good way) that at this time of the year so many growers, all over the country, are still having issues with caterpillars.  It is the second week of winter, in New Zealand, but after a mild autumn with little or no frosts, the outside populations have not regressed.  They are eating their way through a myriad of different cultivars.   Many growers have been using biological insecticides, such as Bacillus Thuringiensis (kurstaki strain), but the general consensus, from conversations I have had with growers, is concern that it is not working as well as it has in the past, they are struggling to eliminate and control these recurring populations.

I was hoping the article I wrote, posted in late March, would have been the final of the year in regards to caterpillars.  Unfortunately, I think the problem still needs to be addressed.  Last week, in fact even on Monday of this week, I have seen countless numbers of caterpillars causing vast amounts of damage.  As if growers don’t have enough to deal with!  At one property the leaf looked like it had been shot at by a double barrel shot gun.  However, what was pleasing to see is that the BT, that was recently applied, had annihilated the caterpillar population.  There appeared to be a 100% success rate. 

The spraying of products, at any time, is not desirable but least of all in winter.  As discussed in other articles, fungus issues are at the forefront of problems with the warm, wet weather we’ve had.  Keeping your plants healthy is a priority.  Don’t overload your plants, it may be warm but light levels are now dipping to the lowest accumulated weekly light sum this calendar year and will be low for the next six to seven weeks.  I would stress that when you are applying BT, you make sure there is not any residual chemicals left over from previous spraying applications in your tanks or hoses.  Make sure you flush out your tanks multiple times before mixing a BT with water. 

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Article Written by Stefan Vogrincic, Consultant, Grower2Grower

Article Edited by Marie Vogrincic, Editor, Grower2Grower