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Beetle products will be welcomed

Some new chemistry is on the way to combat Colorado potato beetles.


November 14, 2007
By Peter Darbishire

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Photo courtesy: USDA photograph by Scott Bauer.

Virtually all potato growers will recall the anguish of tackling Colorado potato
beetles (CPB) using insecticides which were no longer effective due to the development
of resistance. Rotation among available products gave way to unusual or desperate
techniques, such as the use of flamers or vacuums and surrounding fields with
plastic-lined trenches. That was a dozen or so years ago. Then, in 1995, new
chemistry with a new mode of action was introduced. There has been relative
calm in the insect's management since, though growers are now more vigilant
about how they use the products now available.

It is good to know that new products are in the pipeline before widespread
resistance emerges once again. At the Southern Crop Protection and Food Research
Centre of Agriculture and Agri-Food Canada in London, Ontario, entomologist
Dr. Jeff Tolman has been reviewing two products, each with new active ingredients
against CPB. For two years, he has looked at foliar-applied products from DuPont
and BASF. DuPont is developing a new family of insecticides, the anthranilamides.
One member of this group, DPX E2Y45 has been in Tolman's trials for two years;
the other (DPX HGW86) for one season. BASF's metaflumazone insecticide has also
been studied for two years. DuPont will be introducing DPX E2Y45 globally with
the trade name Altacor. BASF's product will be known as Alverde.

The DuPont product selectively targets insect ryanodine receptors. This activation
stimulates release of calcium, causing impaired muscle regulation, paralysis
and ultimately, death. "This quickly stops the insects from feeding, though
they are slow to die," Tolman says. "It will be effective on adults
flying into the crop and on the larvae that hatch from eggs. Altacor was still
effective against larvae placed on leaves following foliar application of Assail."

It is worth noting that in Tolman's tests, treated leaves are collected in
the field, then fed to the beetles to assess mortality and protection and how
long a toxic dose remains. "This test is more severe than the situation
in the grower's field," says Tolman. A grower effectively controlling CPB
with Assail may well not need to spray again for two to three weeks when the
population has risen again to threshold levels. It is active on a wide range
of chewing insects, including lepidoptera (caterpillars), CPB and European corn
borer, which has become an important pest of potatoes in Prince Edward Island.

Altacor also has translaminar activity: if applied to the top of a leaf, it
will translocate to the lower surface. Larvae hatching from CPB eggs that have
the product on them will be affected, since CPB larvae feed on their egg shells.
With its novel mode of activity, Altacor will be effective against insects that
are resistant to other active ingredients. Tolman notes that in his trials,
this product shows the best residual activity since the most effective pyrethroid
insecticides. However, he also advises that since it is not systemic, it only
protects leaves on which it is applied: new growth is not protected.

As with most new chemistries, Altacor is a low dosage product. It is also highly
compatible with other pest management products used on potatoes. Though the
actual formulation is still being developed by DuPont, it will likely be introduced
in a dry flowable formulation. The company does not expect the product to be
registered for the 2007 crop season, but is working towards a global introduction.

Metaflumizone, from BASF, belongs to the semicarbazone class of chemistry (Group
22) and has good to excellent activity on lepidoptera species as well as other
pests of economic importance such as beetles, ants, flies, termites and fleas.
BASF says it has early indications of activity on leafhoppers and plant hoppers
and is pursuing this research further.

Both these products have low levels of toxicity or are non-toxic to non-target
species of insects, including predatory insects and pollinators, as well as
mammalian species, birds, fish and aquatic invertebrates.

The products begin to affect target pests quickly, though death is slower from
products with which growers are accustomed. It is important to scout populations
of pests and to judge threshold levels before application or re-application.

As with all pest control products, the user has a critical role to play in
managing these new products. Tolman recommends they should only be used when
economic thresholds are reached and that they are used in conjunction with other
integrated pest management techniques, including rotating among products with
different modes of action and most importantly, separating potato crops as much
as possible from fields planted to potatoes the previous year, a practice which
reduces the impact from beetles walking into the new crop from overwintering
sites.

Also, label rates should be applied. "Insect populations vary in their
susceptibility to control products," says Tolman. Recommended rates are
designed to kill populations that might survive lower doses: application of
below-label rates could ultimately result in selection for resistant populations.
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Other insects too?
There is consensus about using integrated pest management practices, especially
when it concerns insect control.

"I agree that fields should be scouted and applications only made when
economic thresholds have been reached. It is important to rotate between the
different classes of insecticides to prolong the effectiveness of each insecticide.
Follow-up scouting should always be conducted to verify that the insecticide
was effective in controlling the insect," says Dr. Christine Noronha, research
scientist and entomologist with Agriculture and Agri-Food Canada in Charlottetown,
Prince Edward Island.

"If growers still see beetles and larvae feeding after an application,
they should stop using that particular insecticide until a resistance test is
conducted on the surviving individuals. Rotating a field as far away from the
previous year's field is a good practice, especially if the neighbouring fields
are doing the same thing. These beetles are good walkers and can fly up to a
kilometre or more."

She also emphasizes the need for growers to always stick to the label rates
because using lower than recommended rates could result in the development of
resistance. As far as the new products currently in trials, "We have not
tested DPX E2Y45 on potato beetles but we have tested if for one year on the
European corn borer. We found that applied once at peak oviposition, it effectively
controlled European corn borer and reduced damage in terms of number of holes
per plant.

"Currently, the product Success is registered which is also effective
in controlling European corn borer damage in potatoes. The new product was compared
to Success in the trials," she adds.

Another product waiting in the wings for approval is DuPont's Avaunt, a new
chemistry (indoxacarb) which controls European corn borer larvae (lepidoptera).
Alex Crouse, who heads up DuPont's horticultural products sales for Canada,
believes it will be a useful alternative for potato growers plagued by this
pest. Avaunt contains the active ingredient indoxacarb a new mode of action
that blocks the insect's feeding channel in a similar way to how an anaesthetic
works. Feeding ceases within minutes to hours after ingestion, followed by paralysis
and death. It has a high level of safety to beneficial insects. –

New actives crucial
"It is exciting to see several new effective insect control
products, including E2Y45 and HGW86, coming through the pipeline for potato
producers," says Steve Howatt of Atlantic AgriTech in Prince Edward
Island. "In light of past insecticide resistance and tolerance experiences
with the highly adaptive Colorado potato beetle, growers are now much
more careful in how they use and manage their pest control products. Although
a number of effective products are currently available to help battle
this and other insects, it is crucial that new technologies continually
become available to potato producers."

He adds, "By having a range of new actives available to them, growers
will be better equipped to manage this pest, while minimizing the risk
of resistance. The addition of these new tools to the toolbox will allow
growers to better plan their resistance management strategy by rotating
through several families of products."